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Precision Measurements of the Proton Structure by H1 and ZEUS

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Precision Measurements of the Proton Structure by H1 and ZEUS Powered By Docstoc
					Precision Measurements of the
 Proton Structure by H1 and
           ZEUS


              S. Glazov, DESY,
       for H1 and ZEUS collaborations
                  DIS 2011



                                   1
                    Proton structure probe
                                             Neutral current Deep Inelastic Scatter-
                                             ing (DIS) cross section:
                                                      d2 σ±   2πα2 Y+ ±
                                                            =        σr =
                                                     dxdQ2     Q4 x

                                               2πα2 Y+         2    y2                                                    Y−
                                             =    4x
                                                       F2 (x, Q ) −    F L (x, Q2 )                                          xF3
                                                Q                   Y+                                                    Y+
                                        where factors Y± = 1 ± (1 − y)2 and
                                       y2 define polarisation of the exchanged
                                       boson and y = Q2 /(S x).
Kinematics is determined by boson virtuality Q2 and Bjorken x.
At leading order:                                                   H1 and ZEUS
                                                                   1




                                                             xf
                                                                                                                 Q2 = 10 GeV2
 F2      =    x   e2 (q(x)
                   q        ¯
                          + q(x))
                                                                                               HERAPDF1.0
                                                                  0.8

 xF3     =                      ¯
              x 2eq aq (q(x) − q(x))                                                           exp. uncert.
                                                                                               model uncert.
                                                                                                                           xuv
 σ+           x(¯ + c) + x(1 − y)2 (d + s)
                                                                                               parametrization uncert.

  CC     ∼      u ¯                                               0.6
                                                                                   xg (× 0.05)

 σ−      ∼                          ¯ ¯
              x(u + c) + x(1 − y)2 (d + s)
  CC                                                              0.4
                                                                                                                           xdv
xg(x) — from F2 scaling violation, jets and F L                            xS (× 0.05)

                                                                  0.2




                                                      2             10-4
                                                                                          -3
                                                                                         10              10-2            10-1
                                                                                                                                 x
                                                                                                                                     1
                 HERA, H1 and ZEUS.

                                                        Ee × E p =27.5×920 GeV2
                                                        √
                                                          s = 318 GeV
                                                        L= 5·1031 cm−2 s−1
                                                        e beam polarisation.
                                                                                               Status: 1-July-2007
                                                                                         400




                                                        -1
                                                         H1 Integrated Luminosity / pb
                                                                                                     electrons
                                                                                                     positrons
                                                                                                     low E


                                                                                         300                           HERA-2




                                                                                         200


                                                                                                                                       HERA-1
                                                                                         100




                                                                                           0
                                                                                               0                 500            1000          1500
                                                                                                                                  Days of running



Integrated luminosity: about 500 pb−1 per experiment.



                                           3
       Overview of H1 and ZEUS Results
• High Q2 , high x.
   – Combined Measurement of Neutral and Charged Current Cross
     Sections at HERA, H1prelim-10-141 ZEUS-prel-10-017
   – PDF fits including HERA-II high Q2 data, H1prelim-10-142
     ZEUS-prel-10-018
   – High Q2 NC and CC e+ p measurement using HERA-II data.
     ZEUS-prel-11-003.
   – Measurement of neutral current (e+ p) cross sections at high x using
     HERA-II data, ZEUS-prel-11-004
• Low Q2 , low x.
   – Measurement of the Inclusive e± p Scattering Cross Section at High
     Inelasticity y and of the Structure Function F L . H1 Collaboration,
     Eur.Phys.J.C71 (2011) 1579, 12/10
• Fits using exclusive final states
                                                  cc
   – QCD Analysis of Combined H1 and ZEUS F2 Data,
     H1prelim-10-143 ZEUS-prel-10-019
   – Jets at high Q2 , H1prelim-11-0xx
   – Jet cross sections used in PDF Fit, H1prelim-11-034, ZEUS-11-001


                                              4
                                2
                High Q , high x


            (H1prelim-10-141,ZEUS-prel-10-017),
   (H1prelim-10-142,ZEUS-prel-10-018), ZEUS-prel-10-018,
                     ZEUS-prel-11-004
(Also talks of J. Sztuk-Dambietz, A. Caldwell, S. Trevor, I. Singh)




                                                5
Combined H1 and ZEUS HERA-I-HERA-II measurements
                                                                                                                                                                                                                                                                   talk of J. Sztuk-Dambietz
                                                                               H1 and ZEUS                                                                                                                                        H1 and ZEUS
     σr,CC(x,Q )




                                                                                                                                                                    σr,CC(x,Q )
                                                                                                                                                                                                   2             2            2              2                 2               2         2             2
     2




                                                                                                                                                                    2
                                       2             2                     2             2                      2              2              2             2                             Q = 300 GeV                 Q = 500 GeV                         Q = 1000 GeV              Q = 1500 GeV
                                   Q = 300 GeV                         Q = 500 GeV                             Q = 1000 GeV                  Q = 1500 GeV




                                                                                                                                                                                                                                                                                                               August 2010
                    2                                                                                                                                                              1.5

                   1.5
                                                                                                                                                                      +             1
     -




                    1
                                                                                                                                                                                   0.5
                   0.5




                                                                                                                                                                                                                                                                                                               HERA Inclusive Working Group
                    0                                                                                                                                                               0
                                       2                 2                 2                 2                  2              2              2             2                                     2              2            2                  2             2               2         2             2
                                   Q = 2000 GeV                        Q = 3000 GeV                            Q = 5000 GeV                  Q = 8000 GeV                          0.6    Q = 2000 GeV                Q = 3000 GeV                        Q = 5000 GeV              Q = 8000 GeV

                    1
                                                                                                                                                                                   0.4

                   0.5
                                                                                                                                                                                   0.2


                     0                                                                                                                                                              0
                                                                                                          -2             -1             -2             -1                                                                                                     -2        -1              -2        -1
                   0.8             2                     2             2                     2       10             10             10             10                                                                                                     10        10              10        10
                              Q = 15000 GeV                       Q = 30000 GeV                                                                                 x                 0.15
                                                                                                                                                                                              2
                                                                                                                                                                                         Q = 15000 GeV
                                                                                                                                                                                                                 2        2
                                                                                                                                                                                                                     Q = 30000 GeV
                                                                                                                                                                                                                                                 2                                                         x
                   0.6
                                                                                                                                                        -
                                                                                                                              HERA I CC e p                                        0.1                                                                                       HERA I+II CC e+p (prel.)
                   0.4
                                                                                                                              HERAPDF1.0                                                                                                                                     HERAPDF1.5
                                                                                                                                                                                  0.05
                   0.2

                    0                                                                                                                                                               0
                              -2                -1                -2                -1                                                                                                        -2            -1            -2            -1
                         10                10                10                10                                                                                                        10            10            10            10
                                                                                                 x                                                                                                                                                   x



      • Combination of HERA-I and HERA-II data collected by H1 and ZEUS,
        for CC and NC processes (missing only NC e+ p from ZEUS, which
        comes next!).
      • 674 combined data points with 134 sources of systematic uncertainty.
      • Significantly more precise e± p CC and e− p NC data compared to
        HERA-I combination.


                                                                                                                                                                                                        6
                                                           HERAPDF1.5 Fit
                                                    H1 and ZEUS                                                                                                       talk of A. Caldwell
i




                                                                                                                                  August 2010
σr,NC(x,Q ) x 2


                  10 7
                                                                                                                     +
                                x = 0.00005, i=21
                                                                                       HERA I+II NC e p (prel.)
2




                  10 6               x = 0.00008, i=20                                 Fixed Target
                                       x = 0.00013, i=19
                                           x = 0.00020, i=18                           HERAPDF1.5
                                             x = 0.00032, i=17
  +               10 5                           x = 0.0005, i=16
                                                   x = 0.0008, i=15
                                                       x = 0.0013, i=14                                                                                          • NLO        HERAPDF1.5
                       4                                   x = 0.0020, i=13
                  10
                                                               x = 0.0032, i=12                                                                                    (prel.) fit
                                                                    x = 0.005, i=11
                  10 3                                                 x = 0.008, i=10                                                                           • Good agreement between
                                                                               x = 0.013, i=9
                                                                                   x = 0.02, i=8                                                                   DGLAP prediction and
                  10 2                                                                 x = 0.032, i=7
                                                                                         x = 0.05, i=6
                                                                                                                                                                   the data.




                                                                                                                                  HERA Inclusive Working Group
                  10                                                                            x = 0.08, i=5
                                                                                                    x = 0.13, i=4
                                                                                                                                                                 • Extrapolation to low Q2 is
                   1
                                                                                                        x = 0.18, i=3                                              consistent with fixed tar-
                                                                                                          x = 0.25, i=2
                                                                                                                                                                   get data.
                       -1
                  10                                                                                         x = 0.40, i=1


                       -2
                  10                                                                                         x = 0.65, i=0


                       -3
                  10
                                                       2                   3                    4                    5
                            1   10                10                  10                   10                   10
                                                                                                                     2        2
                                                                                                                Q / GeV

https://www.desy.de/h1zeus/combined results/index.php?do=proton structure


                                                                                                                          7
                            HERAPDF1.0 and HERAPDF1.5 fits                                                                              talk of A. Caldwell
                                  H1 and ZEUS                                            H1 and ZEUS HERA I+II 10 parameter PDF Fit
      1                                                                           1




                                                                                                                                                        March 2011
xf




                                                                            xf
                                                    Q2 = 10 GeV2                                                               Q2 = 10 GeV2

                                  HERAPDF1.0                                                                 HERAPDF1.5 (prel.)
     0.8                                                                         0.8
                                  exp. uncert.                                                               exp. uncert.




                                                                                                                                                        HERAPDF Structure Function Working Group
                                  model uncert.                                                              model uncert.
                                                                                                                                          xuv
                                  parametrization uncert.     xuv                                            parametrization uncert.
     0.6                                                                         0.6
                      xg (× 0.05)


     0.4                                                                         0.4
                                                                                         xg (× 0.05)                                      xdv
                                                              xdv
              xS (× 0.05)

     0.2                                                                         0.2
                                                                                         xS (× 0.05)


                             -3
                                                                                  0                     -3
       10-4                 10              10-2            10-1        1         10-4                 10              10-2             10-1        1
                                                                    x                                                                           x

                                     ¯ ¯
              • Fits parameterise xU, xD, xuv , xdv and g using
                x f (x) = AxB (1 − x)C (1 + Dx + Ex2 ) form.
              • Experimental, model and parameterisation uncertainties are estimated.
              • HERAPDF1.5 fit provides determination of the valence quark densities
                at high x with reduced uncertainties compared to HERAPDF1.0.



                                                                                   8
                                            HERAPDF1.5 NNLO fit                                                                                                          talk of A. Caldwell
             H1 and ZEUS HERA I+II 14 parameter PDF Fit                                                                            H1 and ZEUS HERA I+II PDF Fit
      1                                                                                                                     1




                                                                           March 2011




                                                                                                                                                                                                 March 2011
xf




                                                                                                                      xf
                                                   Q2 = 10 GeV2                                                                                                          Q2 = 10 GeV2

                                 HERAPDF1.5f (prel.)                                                                                                   HERAPDF1.5 NNLO (prel.)
     0.8                                                                                                                   0.8
                                 exp. uncert.                                                                                                          exp. uncert.
                                 model uncert.




                                                                           HERAPDF Structure Function Working Group




                                                                                                                                                                                                 HERAPDF Structure Function Working Group
                                                                                                                                                       model uncert.
                                 parametrization uncert.     xuv                                                                                                                   xuv
                                                                                                                                                       parametrization uncert.
     0.6                                                                                                                   0.6
                                 HERAPDF1.5 (prel.)



     0.4                                                                                                                   0.4
             xg (× 0.05)                                     xdv                                                                    xg (× 0.05)                                    xdv



     0.2                                                                                                                   0.2
             xS (× 0.05)                                                                                                           xS (× 0.05)


      0                     -3
                                                                                                                            0                     -3
      10-4                 10              10-2            10-1        1                                                    10-4             10                  10-2            10-1        1
                                                                   x                                                                                                                     x

           • NNLO QCD fit using fixed αS (MZ ) = 0.1176.
           • Flexible gluon: xg(x) = AxB (1 − x)C − A xB (1 − x)25 .
           • χ2 /Nd.f. is comparable between NLO and NNLO fits: 744.3/660 vs
             735.1/660.
           • HERAPDF1.5NNLO has harder gluon at high x compared to
             HERAPDF1.0NNLO fit.

                                                                                                                            9
                                                ZEUS NC e+ p data
                                     ZEUS                                                                 talk of S. Trevor
∼
σ


         Q 2 = 200 GeV 2      Q 2 = 250 GeV 2      Q 2 = 350 GeV 2     Q 2 = 450 GeV 2
    1



0.5
                                                                                              • ZEUS new preliminary NC
                                                                                                e+ p measurement based on
    0

         Q 2 = 650 GeV 2      Q 2 = 800 GeV 2     Q 2 = 1200 GeV2      Q 2 = 1500 GeV2
                                                                                                complete HERA-II sample.
    1
                                                                                                → last inclusive sample for
0.5                                                                                             HERA-II.
    0
                                                                                              • Data are compared to HERA-
    1
        Q 2 = 2000 GeV2       Q 2 = 3000 GeV2     Q 2 = 5000 GeV2      Q 2 = 8000 GeV2          II e− p sample and predictions
                                                                                                based on HERAPDF1.5 fit.
0.5
                                                                                              • Difference between e− p and
    0                                                                                           e+ p cross sections can be used
        Q 2 = 12000 GeV 2    Q 2 = 20000 GeV 2    Q 2 = 30000 GeV 2   10-2     10-1
    1                                                                  ZEUS NC (prel.)
                                                                       e +p (135.5pb -1)
                                                                                                to measure xF3 and constrain
0.5
                                                                       SM (HERAPDF1.5)
                                                                       P e = 0 (corrected)      valence quarks.
                                                                       ZEUS NC
                                                                       e - p (169.9pb -1)
                                                                       SM (HERAPDF1.5)
    0                                                                  P e = 0 (corrected)

        10-2    10-1        10-2    10-1         10-2    10-1
                                                                x



                                                                                             10
                                          ZEUS Extension to high x
                                                                                                 ZEUS                                                                           talk of I. Singh
                                 10                                   10                               10                                 10


                                     1                     Q2=575      1                    Q2=725      1                     Q2=875       1                     Q2=1025


                                10-1                                  -1                                -1                                 -1




                                          0   0.2   0.4   0.6   0.8    1 0     0.2   0.4   0.6   0.8    1 0      0.2   0.4   0.6   0.8     1 0      0.2   0.4   0.6   0.8   1
                                     1                     Q2=1200     1                    Q2=1400     1                     Q2=1650      1                     Q2=1950
                                     -1                               -1                                -1                                 -1
          d2σ/dxdQ2 [pb/GeV2]   10
                                  -2                                                                   -2                                 -2
                                10
                                  -3                                                                   -3                                 -3
                                10

                                          0   0.2   0.4   0.6   0.8    1 0     0.2   0.4   0.6   0.8    1 0      0.2   0.4   0.6   0.8     1 0      0.2   0.4   0.6   0.8   1
                                     1                     Q2=2250     1                    Q2=2600     1                     Q2=3000      1                     Q2=3500

                                10-1                                  -1                                -1                                 -1


                                  -2                                                                   -2                                 -2
                                10
                                  -3                                                                   -3                                 -3
                                10

                                10-1 0        0.2   0.4   0.6   0.8    1
                                                                      -1   0   0.2   0.4   0.6   0.8    1
                                                                                                       -1    0   0.2   0.4   0.6   0.8     1
                                                                                                                                          -1    0   0.2   0.4   0.6   0.8   1

                                10-2                       Q2=4150                          Q2=4850    -2                     Q 2 =5600   -2                     Q2 =7000
                                  -3                                                                   -3                                 -3
                                10

                                10-4                                                                   -4                                 -4

                                  -5                                                                   -5                                 -5
                                10

                                10
                                  -2      0   0.2   0.4   0.6   0.8    1 0     0.2   0.4   0.6   0.8    1 0      0.2   0.4   0.6   0.8     1 0      0.2   0.4   0.6   0.8   1

                                10
                                  -3                       Q2=9500                          Q2=15500                          Q 2 in [GeV2 ] +
                                                                                                                              ZEUS (prel.) e p 142 pb-1
                                10-4                                                                                                         +
                                                                                                                              ZEUS (prel.) e p 142 pb-1
                                  -5
                                10                                                                                            (Integrated/Averaged)
                                10
                                  -6
                                                                                                                              CTEQ6D
                                          0   0.2   0.4   0.6   0.8    1 0     0.2   0.4   0.6   0.8    1                     HERAPDF 1.5
                                                                                                  x                           ↓ 68% CL




 • Not so many accurate constraints on PDFs at largest x.
 • Resolution of kinematic reconstruction at HERA degrades for
   low y < 0.01
→ Integrated xmin < x ≤ 1 measurement. ZEUS-prel-11-004.


                                                                                                                                   11
                            2
Low x, Low Q , High y


H1 Collab., Eur.Phys.J.C71 (2011) 1579, 12/10
         (Also talk of A. Petrukhin)




                                   12
                            Measurement of Cross Section at High y

                                                                              H1 Collaboration
                                                                                                                                      talk of A. Petrukhin
σr           2
           Q = 1.5 GeV
                                   2             2
                                            Q = 2 GeV
                                                                2            2
                                                                         Q = 2.5 GeV
                                                                                              2     2
                                                                                                   Q = 3.5 GeV
                                                                                                                    2

     1.5                      1.5                              1.5                           1.5


      1                            1                             1                             1


     0.5                      0.5                              0.5                           0.5
                                                                                                                        • Analysis of HERA-II data sample
                   -3
           10-4 2 10        10-2 2      -42          -3    -2 2          -42       -3    -2 2      -4 2   -3   -2 2
                                                                                                                          with dedicated extension to low
             Q = 5 GeV                  Q = 6.5 GeV                      Q = 8.5 GeV               Q = 12 GeV
     1.5                      1.5                              1.5                           1.5
                                                                                                                          Ee → high inelasticity y.
      1                            1                             1                             1
                                                                                                                        • Reduction of the errors at high y
     0.5                      0.5                              0.5                           0.5
                                                                                                                          for E p = 920 by factor of ∼ 2
     1.5
             -4        -3
           Q2 = 15 GeV 2
                              -2

                              1.5
                                        -4
                                        Q2 = 20 GeV2
                                                     -3    -2

                                                               1.5
                                                                         -4        -3
                                                                         Q2 = 25 GeV 2
                                                                                         -2

                                                                                             1.5
                                                                                                   -4     -3
                                                                                                   Q2 = 35 GeV2
                                                                                                               -2
                                                                                                                          compared to HERA-I sample.
      1                            1                             1                             1                        • Reduced proton energy run for
     0.5                      0.5                              0.5                           0.5                          E p = 460 GeV and E p =
             -4
             2
           Q = 45 GeV
                       -3     -2
                                 2           2
                                        Q = 60 GeV1.5
                                                     -3
                                                                2             2
                                                                         Q = 90 GeV
                                                                                   -3
                                                                                              2
                                                                                                          -3              575 GeV.
     1.5            1.5

                                                                                                   Ep = 920 GeV         • Extension of the kinematic reach
      1                            1                                1



     0.5                      0.5                               0.5
                                                                                                   Ep = 575 GeV           to Q2 ≥ 1.5 GeV2 .
                                                                                                   Ep = 460 GeV

             -4        -3     -2        -4           -3    -2            -4        -3    -2
           10     10        10         10        10       10            10        10    10
                                                                                              x
                                                                                               x




                                                                                                                          13
     Measurement of the Structure Function F L
                                                                    H1 Collaboration talk of A. Petrukhin
FL
             0.28


                    0.43

                           0.59


                                  0.88


                                          1.29

                                                 1.69

                                                        2.24


                                                                    3.19

                                                                           4.02


                                                                                  5.40

                                                                                         6.86


                                                                                                10.3

                                                                                                       14.6
            4
            x 10
     0.4



     0.2



       0
                                                                                                   H1
                                         HERAPDF1.0 NLO                           MSTW08 NNLO
                                         CT10 NLO                                 JR09 NNLO
                    ZEUS                 NNPDF2.1 NLO                             ABKM09 NNLO
     -0.2
                    2                                          10                               50
                                                                                          2     2
                                                                                         Q / GeV
Measurement of the structure function F L extended to Q2 ≥ 1.5 GeV2
and compared to predictions from PDF groups. Good agreement,
within the uncertainties.

                                                                           14
Low x phenomenology: DGLAP vs Dipole
                                                                                                                       talk of A. Petrukhin
σr    2           Q2=3.5 GeV2
                                                      H1 Collaboration
                                                    Q2=5 GeV2                  Q2=6.5 GeV2
                                                                                              Compare DGLAP and DIPOLE mod-
     1.5                        1.5                         1.5
                                                                                              els in the region of phase space valid
                                                                                              for both: x < 0.01 and Q2 ≥ 3.5 GeV2 .
       1                              1                         1

     0.5                        0.5                         0.5

                     -3
           10-4 10 2=8.5 GeV2
                       -2
                 Q 10 10
                            -1
                                          10-4 10-3 Q2=12 GeV2
                                                     10-2 10-1      10-4 10-3 Q2 =15 GeV2
                                                                               10-2 10-1        • Three DIPOLE models: GBW,
     1.5                        1.5                         1.5

       1                              1                         1
                                                                                                   IIM and B-SAT and two different
     0.5                        0.5                         0.5                                    DGLAP models for heavy flavors
                     -3
           10-4 10 2=20 GeV2
                      -2
                  Q 10 10
                           -1
                                          10-4 10-3 Q2=25 GeV2
                                                     10-2 10-1      10-4 10-3 Q2 =35 GeV2
                                                                               10-2 10-1           and inclusion of higher orders for
     1.5                        1.5                         1.5

       1                              1                         1
                                                                                                   F L : RT and ACOT.
     0.5                        0.5                         0.5
                                                                                                • Valence quark contribution siz-
                     -3
                      -2   -1
           10-4 10 2=45 GeV2              10-4 10-3 Q2=60 GeV2      10-4 10-3 Q2 =90 GeV2

     1.5
                  Q 10 10
                                1.5
                                                     10-2 10-1

                                                            1.5
                                                                               10-2 10-1
                                                                                                   able even for x < 0.01. Use
       1                              1                         1                                  DGLAP estimate to correct for it.
     0.5

                     -3
                                0.5                         0.5
                                                                                                • Best χ2 /Nd.f. is for ACOT
           10-4 10 2 10-2 10-1            10-4 10-3 2 10-2 10-12    10-4 10-3 10-2 10-1
                 Q =120 GeV2                      Q =150 GeV
     1.5                        1.5                                                                (248/249), followed by IIM
       1                              1
                                                                      Ep
                                                                      Ep
                                                                           = 920 GeV
                                                                           = 820 GeV
                                                                                       σ920
                                                                                        r
                                                                                       σ820
                                                                                                   (259/252) and B-SAT (262/252).
     0.5                        0.5                                   Ep   = 575 GeV
                                                                                        r
                                                                                       σ575
                                                                                        r
           DGLAPvalence                                               Ep   = 460 GeV   σ460
                                                                                        r
      0            -3
                                          10-4 10-3 10-2 10-1
           10-4 10        10-2 10-1
                                                                x




                                                                                                     15
    Inclusive ++ Results


H1prelim-11-0xx, (H1prelim-11-034, ZEUS-11-001),
       (H1prelim-10-143,ZEUS-prel-10-019)
                                           c     e
 (Also talks of R. Kogler, K. Nowak, R. Plaˇ akyt˙ )




                                        16
      Decomposing u and c densities at low x
                                                                                                            c     e
                                                                                              talk of R. Plaˇ akyt˙
 Inclusive structure function F2 is sensitive




                                                F2 c
                                                                     Q2 = 4 GeV 2                  Q2 = 6.5 GeV2                Q2 = 12 GeV2




                                                 c




                                                                                                                                                     August 2010
                                                       0.4
                                                        0.4                           0.4                          0.4

 to
                                                       0.2
                                                        0.2                           0.2                          0.2
                       ¯
        F2 ∼ 4 U + U + D + D ,   ¯
                                                         00                             0                            0




                                                F2 c
                                                                     Q2 = 20 GeV2                  Q2 = 35 GeV2                 Q2 = 60 GeV2




                                                 c
  where U = u + c and D = d + s + b. At low            0.6
                                                        0.6                           0.6                          0.6




                                                                                                                                                     HERA Inclusive Working Group
 x and Q2       2
               mC , contribution of charm to           0.4
                                                        0.4                           0.4                          0.4

                                                       0.2
                                                        0.2                           0.2                          0.2
 F2 reaches 30%.
                                                         00                            0                             0




                                                F2 c
 Determination of charm contribution is a                            Q2 = 120 GeV2                 Q2 = 200 GeV2                Q2 = 400 GeV2




                                                 c
                                                       0.4
                                                        0.4                           0.4                          0.4


 mixed theoretical/experimental problem: it            0.2
                                                        0.2                           0.2                          0.2

 can be calculated given the gluon den-
                                                         00                            0                             0




                                                F2 c
                                                                     Q2 = 1000 GeV2




                                                 c
 sity, however description of the charm                0.3
                                                        0.3                                 10-4      10
                                                                                                         -3
                                                                                                              10-2
                                                                                                                     x
                                                                                                                         10-4     10
                                                                                                                                     -3
                                                                                                                                          10-2
                                                                                                                                                 x
                                                                                                      HERA (prel.)
 threshold is complicated leading to a num-            0.2
                                                        0.2                                           HERAPDF1.0 + Fc c (prel.)
                                                                                                      RT standard
                                                                                                                    2


                                                       0.1
                                                        0.1                                           RT optimised
 ber of matching schemes (RT, ACOT,                                                                   ACOT-full
                                                                                                      S-ACOT-χ
                                                         00                                           ZMVFNS
                                                                           -3
 FONLL...).                                                   10-4      10      10-2
                                                                                       x



                    cc
Combined HERA F2 data reaches 5 − 10% precision per point, can
be used to study different HF models.


                                                       17
                     Scan of mc and Predictions for LHC
                                                 model




                         H1 and ZEUS (prel.)                                                                                                    c     e
                                                                                                                                  talk of R. Plaˇ akyt˙
χ2




                                                                  August 2010
                                           cc
                         HERAPDF1.0 + F2 (prel.)
   1200
                                  RT standard
                                                                                                 All models use a parameter mmodel which is
                                                                                                                               c
                                  RT optimised
                                  ACOT-full
                                  S-ACOT-χ                                                       related to the charm pole mass. Use it as
                                  ZMVFNS
   1000                                                                                          a free parameter to tune the models to the




                                                                  HERA Inclusive Working Group
                                                                                                 charm data.
      800                                                                                        Fits to combined HERA-I inclusive and
                                                                                                   cc
                                                                                                 F2 data using different models for HF
      600                                                                                        treatment.
               1.2         1.4           1.6               1.8
                                          mc    model
                                                        / GeV



          32
                                                                                                 Large ∼ 7% spread of the total pp → Z
σZ / nb




                                                                  August 2010


                Z(   s = 7 TeV)
          31    HERAPDF1.0 + Fcc(prel.)
                              2
                                                                                                 cross section predictions for mmodel scan be-
                                                                                                                                  c
          30                                                                                     tween 1.2 − 1.8 GeV and also for a fixed
                                                                  HERA Inclusive Working Group




          29
                                                                                                 mmodel when considering different models.
                                                                                                   c

          28
                                                                                                 However, the spread is reduced to < 1.0%
                                                   RT standard
                                                   RT optimised
                                                   ACOT-full
                                                                                                 (excluding ZMVFNS) when predictions
          27                                       S-ACOT-χ
                                                   ZMVFNS
                                                                                                 are evaluated at the mmodel (opt) values.
                                                                                                                        c
          26
               1.2          1.4          1.6                1.8
                                                mcmodel
                                                          / GeV




                                                                                                         18
                                                                               Combined DIS+Jets Fit
                                                                H1 and ZEUS (prel.)                                                                                                                                                        H1 and ZEUS (prel.)
                                                                                                                                                                                                                                                                           talk of K. Nowak
                                                                                           H1 data




                                                                                                                           March 2011




                                                                                                                                                                                                                                                                                               March 2011
                                                           PDF uncertainty                                                                                                                                                       PDF uncertainty                    ZEUS data
                                                1.4                            1.4         Eur. Phys. J. C65, 363 (2010)
                                                                                                                                                                                                                      1.4                             1.4
ratio to NLO (NLOJet++ ⊗ HERAPDF1.6 free α s)




                                                                                                                                                                      ratio to NLO (NLOJet++ ⊗ HERAPDF1.6 free α s)
                                                                                                                                                                                                                                                                    Nuc. Phys. B765 (2007)
                                                           scale uncertainty
                                                                                                                                                                                                                                 scale uncertainty
                                                1.2                            1.2                                                                                                                                    1.2                             1.2
                                                  1                              1                                                                                                                                      1                               1
                                                0.8                            0.8                                                                                                                                    0.8                             0.8
                                                                     0.6
                                                0.6 150 < Q2 < 200 GeV2              200 < Q2 < 270 GeV2                                                                                                              0.6                    0.6
                                                                                                                                                                                                                            125 < Q2 < 250 GeV2             250 < Q2 < 500 GeV2

                                                1.4                            1.4                                                                                                                                    1.4                             1.4




                                                                                                                           HERAPDF Structure Function Working Group




                                                                                                                                                                                                                                                                                               HERAPDF Structure Function Working Group
                                                1.2                            1.2                                                                                                                                    1.2                             1.2
                                                  1                              1                                                                                                                                      1                               1
                                                0.8                            0.8                                                                                                                                    0.8                             0.8
                                                                     0.6
                                                0.6 270 < Q2 < 400 GeV2              400 < Q2 < 700 GeV2                                                                                                                                    0.6
                                                                                                                                                                                                                      0.6 500 < Q2 < 1000 GeV2 1000 < Q2 < 2000 GeV2


                                                1.4                            1.4                                                                                                                               2.5                    2.5
                                                                                                                                                                                                                   2                      2
                                                1.2                            1.2
                                                                                                                                                                                                                 1.5                    1.5
                                                  1                              1                                                                                                                                 1                      1
                                                0.8                            0.8
                                                                                                                                                                                                                 0.5                    0.5
                                                                                                                                                                                                                   0                      0
                                                0.6 700 < Q2 < 5000 GeV2 5000 < Q2 < 15000 GeV2
                                                                      0.6                                                                                                                                       -0.5 2000 < Q2 < 5000 GeV2
                                                                                                                                                                                                                                       -0.5                      Q2 > 5000 GeV2

                                                      10               ET [GeV]       10                      ET [GeV]                                                                                                      10                     ET [GeV] 10                      ET [GeV]

                  • Fit combined inclusive HERA I+II data and add to this fit published
                    inclusive jet samples from H1 and ZEUS.
                  • Good description of the jet cross sections: HERAPDF1.6 set.

                                                                                                                                                                                                                            19
                     Combined Jet+DIS inclusive fit and αS (mZ )                                                                                                                                                                                                                                    talk of K. Nowak
             H1 and ZEUS HERA I+II 14 parameter PDF Fit                                                                                 H1 and ZEUS HERA I+II PDF Fit                                                                                                       H1 and ZEUS HERA I+II PDF Fit with Jets
      1                                                                                                                         1                                                                                                                                    1




                                                                               March 2011




                                                                                                                                                                                                                   March 2011




                                                                                                                                                                                                                                                                                                                                                                                        March 2011
xf




                                                                                                                          xf




                                                                                                                                                                                                                                                               xf
                                                       2           2                                                                                                             2           2
                                                   Q = 10 GeV                                                                                                                Q = 10 GeV                                                                                                                            Q2 = 10 GeV2

                                 HERAPDF1.5f (prel.)                                                                                                       HERAPDF1.5f (prel.)                                                                                                                   HERAPDF1.6 (prel.)
     0.8                                                                                                                       0.8                         free αs(M )                                                                                              0.8                          free αs(M )
                                 exp. uncert.                                                                                                                        Z                                                                                                                                     Z
                                 model uncert.                                                                                                             exp. uncert.                                                                                                                          exp. uncert.




                                                                               HERAPDF Structure Function Working Group




                                                                                                                                                                                                                   HERAPDF Structure Function Working Group




                                                                                                                                                                                                                                                                                                                                                                                        HERAPDF Structure Function Working Group
                                 parametrization uncert.     xuv                                                                                           model uncert.               xuv                                                                                                       model uncert.                                                            xuv
                                                                                                                                                           parametrization uncert.                                                                                                               parametrization uncert.
     0.6                                                                                                                       0.6                                                                                                                                  0.6
                                 HERAPDF1.5 (prel.)



     0.4                                                                                                                       0.4                                                                                                                                  0.4
             xg (× 0.05)                                     xdv                                                                       xg (× 0.05)                                     xdv                                                                                  xg (× 0.05)                                                                                   xdv



     0.2                                                                                                                       0.2                                                                                                                                  0.2
             xS (× 0.05)                                                                                                               xS (× 0.05)                                                                                                                          xS (× 0.05)


      0                     -3
                                                                                                                                0                     -3
                                                                                                                                                                                                                                                                     0                     -3
      10-4                 10              10-2            10-1            1                                                    10-4                 10              10-2            10-1                      1                                                     10-4                 10               10-2                10-1                                                 1
                                                                       x                                                                                                                                   x                                                                                                                                                                    x


                Fix αS , no jets                                                                                                        Free αS , no jets                                                                                                                     Free αS , + jets
                                                                                                                                                                                                                                                              H1 and ZEUS (prel.)




                                                                                                                                                                                                                                                                                                                               March 2011
                                                                                                                                                                                                           20
                      • Freeing αS in fits increases xg(x) uncertainty




                                                                                                                                                                                                      min
                                                                                                                                                                                                                                                                                 HERAPDF1.5f




                                                                                                                                                                                                 χ2 - χ2
                        at low x due to large xg(x)-αS correlation.




                                                                                                                                                                                                                                                                                                                               HERAPDF Structure Function Working Group
                                                                                                                                                                                                           15
                                                                                                                                                                                                                                                                                 HERAPDF1.6
                      • Inclusion jets allows to reduce this correlation                                                                                                                                   10
                        and improve uncertainty.
                                                                                                                                                                                                               5
                      • αS (MZ )    =      0.1202 ± 0.0013(exp) ±
                        0.0007(mod)        ±     0.0012(had)+0.0045 (th).
                                                              −0.0036                                                                                                                                          0

                                                                                                                                                                                                                                                  0.114 0.116 0.118             0.12            0.122 0.124 0.126
                                                                                                                                                                                                                                                                                                          αS(M )
                                                                                                                                                                                                                                                                                                                           Z




                                                                                                                                                                               20
                                              ¯
                       HERA PDF Compared to p p and pp Jets
                                         Tevatron Jet Cross Sections                                                                  1.5                      ATLAS Preliminary       ∫ L dt=37 pb




                                                                                                                 Ratio wrt CTEQ 6.6
                                                                                                                                                                                                         -1
                                                                                                                                               |y | < 0.3
                       2.5
 Ratio to HERAPDF1.0

                                                                                                                                                                                        s =7 TeV
                                 |y | < 0.4                           0.4 < |y | < 0.8
                                  jet                                        jet
                        2                                                                                                              1                                               anti-kt    jets, R=0.4

                       1.5                                                                                                                                                                    Data with
                                                                                                                                      0.5                                                     statistical error

                        1
                                                                                                                                      1.5   0.3 < |y | < 0.8
                                                                                                                                                                                              Systematic
                                                                                                                                                                                              uncertainties
                       0.5

                       2.5                                                                                                             1                                               NLO pQCD ×
                                                                                                                                                                                       Non-pert. corr.
                                 0.8 < |y | < 1.2                     1.6 < |y | < 1.6
                                        jet                                  jet
                        2
                                                                                                                                      0.5                                                     CTEQ 6.6

                       1.5
                                                                                                                                      1.5   0.8 < |y | < 1.2                                  MSTW 2008
                        1

                       0.5                                                                                                             1                                                      NNPDF 2.1


                       2.5                                                                                                                                                                    HERAPDF 1.5
                                                                                                                                      0.5
                                               1.6 < |y | < 2.0                     2.0 < |y | < 2.4
                                                          jet                                  jet
                        2
                                                                                                                                      1.5   1.2 < |y | < 2.1
                       1.5
                                                                                          HERAPDF1.0
                        1
                                                                                          D0 RunII                                     1
                       0.5
                                                                                                                                      0.5
                        0                                                                                                                                                          3
                             0          200         400         600         200          400            600                                      102                          10
                                                                                         PT      jet
                                                                                                       [Gev/c]                                                               p [GeV]
                                                                                                                                                                              T




• HERAPDF sets do not include jet data, yet gives satisfactory
  description of these data.
• For Tevatron (D0), HERAPDF is somewhat below predictions,
  for ATLAS, HERAPDF provides the best description of the data.


                                                                                                                 21
 H1 Measurement of Inclusive and Multi-jets
                                                                  talk of R. Kogler




 • New measurement of inclusive and multi-jet cross section for
   150 < Q2 < 15000 GeV2 .
 • Compared to predictions from recent PDF sets: CT10, NNPDF2.1,
   HERAPDF1.5
→ Some preference for HERAPDF1.5, mostly due to high x high Q2 bins
  were CT10, NNPDF2.1 are high due to Tevatron jet data.

                                              22
                          Summary
 • Many new results from HERA during last year
 • New HERA-II data improve precision at high x, in particular for
   uv .
 • Combination of the H1 and ZEUS data brings ultimate precision
   for PDFs. PDF analysis is performed at NLO and NNLO.
 • New H1 results provide F L measurement down to
   Q2 = 1.5 GeV2 , new input for low x phenomenological analyses.
 • Combined charm data fix heavy flavour models parameter
   variation, reduce PDF uncertainties for the LHC predictions.
 • Fit to inclusive + DIS-jet data provides determination of αS (MZ )
   with consistent treatment of PDF uncertainties.
→ HERA continues to provide data essential for physics at the LHC.
The data is the main ingredient for all modern PDF fits. HERAPDF
fits provide alternative PDF sets with well understood experimental
and theory uncertainties.



                                           23
EXTRAS




         24
                       HERAPDF1.5 and HERAPDF1.5f fits
             H1 and ZEUS HERA I+II 10 parameter PDF Fit                                                                            H1 and ZEUS HERA I+II 14 parameter PDF Fit
      1                                                                                                                     1




                                                                           March 2011




                                                                                                                                                                                                 March 2011
xf




                                                                                                                      xf
                                                   Q2 = 10 GeV2                                                                                                          Q2 = 10 GeV2

                                 HERAPDF1.5 (prel.)                                                                                                    HERAPDF1.5f (prel.)
     0.8                                                                                                                   0.8
                                 exp. uncert.                                                                                                          exp. uncert.
                                                                                                                                                       model uncert.




                                                                           HERAPDF Structure Function Working Group




                                                                                                                                                                                                 HERAPDF Structure Function Working Group
                                 model uncert.
                                                             xuv                                                                                       parametrization uncert.     xuv
                                 parametrization uncert.
     0.6                                                                                                                   0.6
                                                                                                                                                       HERAPDF1.5 (prel.)



     0.4                                                                                                                   0.4
             xg (× 0.05)                                     xdv                                                                   xg (× 0.05)                                     xdv



     0.2                                                                                                                   0.2
             xS (× 0.05)                                                                                                           xS (× 0.05)


      0                     -3
                                                                                                                            0                     -3
      10-4                 10              10-2            10-1        1                                                    10-4                 10              10-2            10-1        1
                                                                   x                                                                                                                     x

                                    ¯ ¯
             • Fits parameterise xU, xD, xuv , xdv and g using
               x f (x) = AxB (1 − x)C (1 + Dx + Ex2 ) form.
             • Recently fits were extended from 10 to 14 parameters, by relaxing
               assumptions that Buv = Bdv , using extra term for uv and flexible
               parameterisation for the gluon: xg(x) = AxB (1 − x)C − A xB (1 − x)25 .
      → similar overall errors, more flexible shapes (important for NNLO).


                                                                                                                           25
                       Measurement of the ratio R
                                                               H1 Collaboration
  R                    2
                      Q = 2 GeV   2               2
                                                 Q = 2.5 GeV  2
                                                                            Q2= 3.5 GeV2
      1.5
        1
                           R=0.25
      0.5                                                                                     • Measurements
        0
                       2
                           R=0
                                  2               2           2              2           2
                                                                                                of the structure
                      Q = 5 GeV                  Q = 6.5 GeV                Q = 8.5 GeV
      1.5                                                                                       function     FL
        1
      0.5                                                                                       and F2 can be
        0                                                                                       presented as a
                      Q2= 12 GeV2                Q2= 15 GeV2                Q2= 20 GeV2
      1.5                                                                                       measurement of
        1
      0.5
                                                                                                the ratio
        0
                                                                                                      FL
      1.5
                       2
                      Q = 25 GeV   2              2
                                                 Q = 35 GeV   2              2
                                                                            Q = 45 GeV   2
                                                                                                 R=          .
        1
                                                                   H1 Data                          F2 − F L
                                                                   ACOT
      0.5
        0
                 -4              -3         -4              -3         -4               -3
            10              10         10              10         10               10
                                                                                          x
For Q2 ≥ 3.5 GeV2 , data are consistent with constant R = 0.26 ± 0.05




                                                                       26
                    Low x phenomenology: λ fit
                                                          R     y
    • Using R = 0.26, calculate F2 = σr 1 −              1+R 1+(1−y)2

    • Fit F2 in each Q2 bin assuming (modified) power-law behaviour:
                                                  ln x
                                    F2 = Cx−λ+λ

               H1 Collaboration                                   H1 Collaboration
λ   0.4
          b)                                  λ’ 0.02
                                              λ’             b)
    0.3                                            0.01
    0.2
                                                         0
    0.1                  H1 Data
                                                  -0.01
     0                   Line fit
                                                  -0.02 -1
     10-1       1      10         102                 10            1    10         102
                            Q2 / GeV2                                         Q2 / GeV2
Offset-method fit assuming λ = 0              Offset-method fit assuming λ = 0.25
       χ2 /do f = 538/350                          χ2 /do f = 464/350

Rise of F2 is tamed compared to pure power-law for Q2 ≤ 10 GeV2 .


                                                    27

				
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