The HERMES Spectrometer The HERMES Spectrometer_

Document Sample
The HERMES Spectrometer The HERMES Spectrometer_ Powered By Docstoc
					     hermes                                                                              HERMES and the Spin of the Nucleon
The HERMES Spectrometer:
m
           Spectrometer                                         FIELD CLAMPS                                 TRIGGER HODOSCOPE H1
                                                                                                                                                                                                                                                                                                                      Internal Gas Target:                                                                                                      Luminosity and Polarisation 1995 − 2000
                                       FRONT                                                DRIFT CHAMBERS                  270 mrad
2                                      MUON
                                                                                                                                                                                                                                                                                                                   polarised Gases: H, D, He                                                                                           7




                                                                                                                                                                                                                                                                                                                                                                                                              Accumulated DIS [·10 ]
                                                                                                                                                                                                                                    170 mrad




                                                                                                                                                                                                                                                                                                                                                                                                              6
                                       HODO
                                                                                                                                  PRESHOWER (H2)
                                                                                                                                                                                                                                           £¡£¡£¡£¡
                                                                                                                                                                                                                                            ¡¡¡¡£¤£¤
                                                                                                                                                                                                                                          ¤¡¤¡¤¡¤¡
                                                                                                                                                                                                                                         £¡£¡£¡£¡£¤
                                                                                                                                                                                                                                      ¤£¤¡¤¡¤¡¤¡                                                                                                                                                                                                              →
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               Hermes 2000 Online Analysis                                                     60
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               40


1
                                    DRIFT
                                   CHAMBERS
                                                                                                                                                                                                                                      ¡£¡£¡£¡£¤
                                                                                                                                                                                                                                    £¤¡£¡£¡£¡£¤
                                                                                                                                                                                                                                    ¡¤¡¤¡¤¡   ¤¡¤¡¤¡     140 mrad
                                                                                                                                                                                                                                                                                                                      unpolarised Gases:                                                                                               6        1995 (e++3He)= 2.3 ·106 DIS
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  +
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            2000 (e + d)
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        →
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               20

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    850                         950                      1050


                                                FC 1/2
                                                                                                                                                                                                                                   ¡£¡£¡£¡£¤
                                                                                                                                                                                                                                   £¡¤¡¤¡¤¡
                                                                                                                                                                                                                                ¤£¤¡£¡£¡£¡
                                                                                                                                                                                                                                ¡¤¡¤¡¤¡£¤                                                                            H2, D2, He, N2, Ne, Kr                                                                                            5
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               60
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               40
                                                         PROP.                                                                                                                                                                £¤¡£¡£¡£¡ ¢
                                                                                                                                                                                                                              ¡¤¡¤¡¤¡
                                                                                                                                                                                                                              ¡ ¡ ¡ ¡ ¢
                                                                                                                                                                                                                              ¡¢¡¢¡¢¡
                                                                                                                                                                                                                          ¢ ¢¡ ¡ ¡ ¡                     27.5 GeV
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               20


                                                                                                                                                                                                                                                                                                                               PID:
                                                      CHAMBERS                                                                                                            LUMINOSITY                                                                                                                                                                                                                                                   4                                                                                                                                         1000                       1175                         1350
0                                                                                                                                                                                                                         ¡¢¡¢¡¢¡ ¢                                                                                                                                                                                                                                                                                                                                            60
                                                                                                                                                                          MONITOR
     TARGET                                                MC 1-3                                                                                                                                                        ¢¡ ¡ ¡ ¡ ¢
                                                                                                                                                                                                                        ¡¢¡¢¡¢¡                          e+                                                                                                                                                                                                                                                                                                                    40
      CELL
              SILICON
                      HODOSCOPE H0
                                        DVC                                                                                                                                                                             ¡¢¡¢¡¢¡
                                                                                                                                                                                                                       ¡ ¡ ¡ ¡ ¢
                                                                                                                                                                                                                    ¢ ¢¡ ¡ ¡ ¡
                                                                                                                                                                                                                    ¡¢¡¢¡¢¡ ¢                                                                                   TRD + Calo + Preshower + RICH                                                                                          3                                                                                                                                       20

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 1300                       1400                         1500
-1                                                                                      BC 1/2                                                                                                                     ¢¡ ¡ ¡ ¡ ¢
                                                                                                                                                                                                                  ¡¢¡¢¡¢¡                                                                                                                                                                                                                                                                                           +   →                                                      60


                       STEEL PLATE
                                                                                                              BC 3/4        TRD                                CALORIMETER
                                                                                                                                                                                                                 ¡ ¡ ¡ ¡ ¢
                                                                                                                                                                                                                  ¡¢¡¢¡¢¡
                                                                                                                                                                                                              ¢ ¢¡ ¡ ¡ ¡
                                                                                                                                                                                                              ¡¢ ¢ ¢                                     140 mrad                                               lepton identification eff. > 98%                                                                                       2

                                                                                                                                                                                                                                                                                                                                                                                                                                                                              →
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       1997 (e + p)

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               →
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               40
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               20
                                                                                                                                                                                                                                                                                                                                                                                                                                                                    1996 (e++ p)                                                     -
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         1998/99 (e + d)
                                                                                                                                                                                                                                                                                                                  hadron contamination: < 1%
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 1450                       1650                         1850
                                                                                                     RICH                                                                                                 IRON WALL                                                                                                                                                                                                                    1                                                                                                                                       60
-2                                                                                                                                                                                                                                                     170 mrad                                                                                                                                                                                                                                                 →
                                                                                                                          270 mrad                                                                                                                                                                                                                                                                                                                                                             1999 (e++ d)                                                                    40
                                                                                                                WIDE ANGLE
                                                                                                                                                                                            MUON HODOSCOPES                                                                                                                                                                                                                                                                                                                                                                    20
                                                                                                              MUON HODOSCOPE                                                                                                                                                                                                                                                                                                           0
                                                                                            MAGNET                                                                                                                                                                                                                                                                                                                                         0               50               100                  150                     200              250                                   1800                        2025                         2250
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     Days of Running
                  0                         1               2             3             4            5           6                7                                                8                      9                                       10 m




                                                The Quark Polarisations ∆q                                                                                                                                                                                                                                                                                                                   The Gluon Polarisation ∆G

Flavour Separation: Use correlation                                                                                                                                                                                                                                                                                                             Direct Determination: Isolate Photon−Gluon Fusion process
between struck quark and detected hadron
                                                                                                                                                                                                                                                                                                                                                                                                                                                                            Select pairs of high pT hadrons
                                         ¯          ¯
                                   ∆u, ∆ u , ∆ d, ∆ d , ∆ s, ∆ ¯
                                                               s
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    Nh± − Nh±
                         e q (x,Q )∫dz D (z,Q ) ∆q(x)                                  2                 2                    h                                                    2
                                                                                                                                                                                                                                                                                                                                                                                                                                                                            A|| =           ~ − ∆G
     A (x,Q ) = C * Σf
                h                           2                                            f f                                    f
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  Nh± + Nh±      G
              1
                       Σ e q (x,Q2)∫dz Dhf’(z,Q2) q(x)                              f’
                                                                                       2
                                                                                          f’ f’
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                Estimated relative contributions
                                                                                                                                                                                                                                                                                                                                  First negative asymmetry in DIS                                                                                                                                               using PYTHIA
                                                          Pqh(x,z)
                                                                                                                                                                                                                                                                                                                                                                  1



                                                                                                                                                                                                                                                                                                                                                  A||(pT ,pT )
                                                                                                                                                                                                                                                                                                                                                 h2
                                        To extract Quark Polarisations solve




                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         fi (i = QCDC, PGF, VMD)
                                                                                                                                                                                                                                                                                                                                                                           pT >1.5 GeV/c
                                                                                                                                                                                                                                                                                                                                                                 0.8         h1


                                                                                                                                                                                                                                                                                                                                                 h1
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    1      pT >1.5 GeV/c
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               h1
                                                                                                                                                                                                                                                                                                                                                                 0.6


                                                                                            A=PQ
                                                                                                                                                                                                                                                                                                                                                                 0.4                                                                                                                                                                                                                            fPGF
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   0.8                          fQCDC
                                                                                                                                                                                                                                                                                                                                                                 0.2
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                fVMD
                                                                                                                                                                          HERMES ∆q extraction  MC projection                                                                                                                                                    0
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   0.6
                                                                                                                                      x (∆u + ∆u)




               Hermes preliminary (1995 - Spring 1999)                                                                                                              0.5                      →                →
                                                                                                                                                                                                                                                                                                                                                            -0.2
                                                                                                                                  –




     0.75                                                                                                                                                                     MC: 96/97 H + 98-00 D
                                                                                                                                                                              HERMES publ. PLB 464 (1999) 123
                           –
                  (∆u+∆u)/(u+u)
                                   –
                                                                                     Quark polarisations                                                  0.25                                                                                                                                                                                              -0.4
        0.5                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        0.4
                                                                                     extracted from the                                                              0                                                                                                                                                                                      -0.6
     0.25
                                                                                     1995−1999 data
                                                                                                                                      x (∆d + ∆d)




                                                                                                                                                          0.25
                                                                                                                                  –




                                                                                                                                                                                   CTEQ4LQ / (1+R)                                                                                                                                                          -0.8
         0                                                                                                                                                                         GRSV 2000 / (1+R)
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   0.2
                                                                                                                                                                     0
                                                                                                                                                                                                                                                                                                                                                                  -1
                                                                                                                                                                                                                                                                                                                                                                           0.6         0.8   1           1.2                                   1.4         1.6  1.8
                                                                                                                                                                                                                                                                                                                                                                                                                                                      h2
        0.5                –       –
                                                                                                                                                      -0.25                                                                                                                                                                                                                                                                                          pT    (GeV/c)
                  (∆d+∆d)/(d+d)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     0
                                                                                                                                                          0.05
                                                                                                                                                                                                                                                                                                                                  Possible contributing processes:                                                                                                                                                                                                        0.6             0.8     1       1.2         1.4         1.6  1.8
                                                                                                                                      x ∆u
                                                                                                                                  –




                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             h2
         0                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  pT    (GeV/c)
                                                                                                                                                                     0
     -0.5


         -1                                                                                                                                               0.05
                                                                                                                                      x ∆d
                                                                                                                                  –




         0
                  ∆qs/qs
                                                                                            MC − prediction for
                                                                                                                                                                     0
                                                                                                                                                                                                                                                                                                                                       ADIS ~ ∆q/q                                                                                     AVMD ~ 0                                                                                                                    ∆G/G is positive
                                                                                                                                                                                                                                                                        M. Beckmann, J. Wendland, HERMES 2001




                                                                                            Polarised PDFs based                                          0.05
                                                                                                                                      x ∆s = x ∆s
                                                                                                                                  –




         -1
                                                                                            on the measured data
                                                                                            from1995−2000
                                                                                                                                                                     0
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    ∆G/G = 0.41± 0.18 ± 0.03
         -2                                                                                                                                           -0.05
                                                                                                                                                          0.02                                                0.1                                                   0.7
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        Strong model dependence for ∆G/G extraction
                                                                                                                                                                                                                                                                                                                                       AQCDC ~ ∆q/q                                                      APGF ~ −∆G/G
          0.02                                  0.1                       0.6
                                                                          x                                                                                                                                                                                          x
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        Factor 2 smaller error bar with 1998 − 2000 data



                                                                                                                                                                                                                                                                                                                    ∆q       ∆G

                                                                                                                                                                                                                                                                                                                 Lg
                                                                     Exclusive Reactions                                                                                                                                                                                                                                        δq                                                                                                                         Transversity
                                                                                                                                                                                                                                                                                                                        Lq
     Analysis of hard exclusive processes leads to a
                                                                                                                                                                                                                                                                                                                                                 Completely unknown quantities δqf(x) and H1⊥(z)
     new class of parton distributions
                                                                                                                                                                                                                                                                                                                                                                                        can only be measured in semi−inclusive DIS
                                                   ˜ ˜
           Generalised Parton Distributions H, H, E, E                                                                                                                                                                                                                                                                                                                                       chiral odd distribution functions δqf(x)
     Total quark angular momentum via second moments                                                                                                                                                                                                                                                                                                                                         chiral odd fragmentation function H1⊥(z)
      Jq = ½ ∆Σ + Lq = ½ ∫x dx (Hq (x,ξ,t=0) + Eq(x,ξ,t=0))                                                                                                                                                                                                                                                                            Prediction:
                                                                                                                                                                                                                                                               γ

                                                                                                                       γ∗                                                                        γ
                                                                                                                                                                                                                                                                                                                                       2001−2003 transversely polarised hydrogen target ⇒ 7*106 DIS
 Simplest Process:                                                                                                                                                                                                          l                                      l’


 Deeply Virtual Compton Scattering                                                                                            k- ∆
                                                                                                                                 2
                                                                                                                                                                               k+∆
                                                                                                                                                                                 2                                                                                                                                                                                                      Aπ+p(x,y,z) =                                                               PT Dnn δu(x) H1⊥(z)
                                                                                                                                                                                                                    P- ∆                                           P+∆

 Isolate via BH−DVCS interference
                                                                                                                       P- ∆
                                                                                                                          2
                                                                                                                                                                                            P+∆
                                                                                                                                                                                              2
                                                                                                                                                                                                                       2                                             2
                                                                                                                                                                                                                                                                                                                                                                                                                                                                            u(x) D1(z)
                                                                                                                                                                                                                                                                                                                                                                                         1                                                                      3                                                        2.5
                                                                                                                                                                                                                                                                                                                                                                                  +




                                                                                                                                                                                                                                                                                                                                                                                                                                                      δu(x)




                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                (z)/Du(z)
                                                                                                                                                                                                                                                                                                                                                                                 AT
                                                                                                                                                                                                                                                                                                                                                                                  π




                                                                                                                                                DVCS                                                      Bethe−Heitler                                                                                                                                                                                                                a)                                                       b)                                                                        c)
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     1




                                                                                                                                                                                                                                                                                                                                                                                       0.8   0.2<z<0.3                                                      2.4                                                             2
                                                                                                                                                                                                                                                                                                                                                                                             0.3<z<0.5
                                                                                                                                                                                                                                                                                                                                                                                             0.5<z<0.7
                                                                                                                                                                                                                                                                                                                                                                                       0.6   0.7<z<1.0                                                      1.8                                                          1.5
                                                                                                                                                                                                          2
                                                                                                         x                                                                                       ∆
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                (1)u




              ALU ~ sin(Φγ) x ℑ F1 H 1                                                                                            ˜                                                                                                                                                                                                                                                    0.4                                                                  1.2                                                             1
                                                                                                                     F1       F2 H 1                                                                                     F2 E 1
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                H⊥
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 1




                                                                                                                                                                                                                                                                                                                                                                                       0.2                                                                  0.6                                                          0.5
                                                                                                                                                                                                                2
                                                                                                     2 x                                                                                     4M                                                                                                                                                                                          0
                                                                                                                                                                                                                                                                                                                                                                                                         -1
                                                                                                                                                                                                                                                                                                                                                                                                                                                                0
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       -1
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            0
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                0                                   0.5              1
                                                                                                                                                                                                                                                                                                                                                                                                    10                                                                            10
                                                                                                                                                                                                                                                                                                                                                                                                                                                 x                                                          x                                                                       z
                                                                                                                                                                                       →+
                                                                                                                                                                                       e p→e γX
                                                                                                                                                                                                     +
                                                                                                                                                                                                                  (0.4 < Mx < 1.4 GeV)

                                                                                                                                                                                                                                                                                                                                       What do we know already ?
φ




                                                                                                                                            Single Spin Asymmetry
  LU
 Asin




         0.6          →+                                                                                                                                                                                                                 FIT BY: P1 + P2 sin(φ)
                       e p → e+γ X                                                                                                                                    0.6
                                                                                      Single Spin                                                                                                                                        P1 = 0.07 ± 0.03
                                                                                                                                                                                                                                         P2 = -0.20 ± 0.05
         0.4
                                                                                      Asymmetry                                                                       0.4                                                                χ /ndf = 1.49
                                                                                                                                                                                                                                          2
                                                                                                                                                                                                                                                                                                                                                        π0
                                                                                                                                                                                                                                                                                                                                                        π+
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       Even with long. pol. H−target
                                                                                                                                                                                                                                                                                                                                       0.05
                                                                                                                                                                                                                                                                                                                                                        π-

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           AULsinφ ≠ 0
         0.2                                                                                                                                                          0.2
                                                                                                                                                                                                                                                                                                                                sinφ




                                                                                                                                                                          0
                                                                                                                                                                                                                                                                                                                                       UL




              0

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    AULsinφ ~ ST Σfe2fh1f(x) H1⊥f(z)
                                                                                                                                                                                                                                                                                                                                 A




                                                                                                                                                                                                                                                                                                                                            0
                                                                                                                                                                     -0.2
        -0.2
                                                                                                 Φ Dependence                                                        -0.4
        -0.4
                                                                                                                                                                                       HERMES                         PRELIMINARY                                                                                                                                                                                                                                                                           ST: transv. target spin component with
                                       HERMES             PRELIMINARY                                  of SSA                                                                                                                                                                                                                          -0.05


        -0.6
                                                                                                                                                                     -0.6                                                                                                                                                                       0.2                0.4           0.6         0.1              0.2                                0.25         0.5    0.75         1                              respect to γ*
                                                                                                                                                                              -3            -2           -1                 0                   1          2            3                                                                                              z                            x                                                       P⊥ (GeV)
                      -1       0        1       2     3     4    5    6         7
                                                                                                                                                                                                                                                          φ [ rad ]
                                                                    Mx (GeV)                                                                                                                                                                                                                                                                                     Spin dependent Collins fragmentation function H1⊥u(z) > 0
                      Measure 2004 − 2005 with new Recoil Detector
                                                                                                                                                                                                                                                                                                                                                                                                                                                           h1 can be measured
                             to improve exclusivity of data


                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        iihttp://hermes.desy.de
                                                      Deutsches Elektronen-Synchrotron
     DESY
                                                      Hamburg, Germany

				
DOCUMENT INFO
Shared By:
Categories:
Tags: Hermes
Stats:
views:14
posted:8/7/2010
language:English
pages:1
Description: Hermes, the French fashion brand, early in order to create a well-known senior horses in Paris, France, and after the introduction of the bags, clothing, scarves, perfume, enamel, jewelry and household goods, make the brand more comprehensive diversity. hermes is also the ancient Greeks called Mercury.