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					                                         Physics results from HERA-B
                                                                  Martin Bräuer, HERA-B

                   Contents:                                         H1/Hamburg seminar
                    • HERA-B:
                        •The goals of HERA-B
                        • The Detector
                        • The Vertexdetector
                        • How to measure
                    • Measuring σ bb with the data collected in the year 2000
                        • Motivation & theory
                        • The data sample
                        • The Method
                        • The Measurement
                    • The data of the year 2002/3
                        • σ bb measurement
                        • Charmonium                                             HERA
                        • Min-bias, open charm
                    • Summary and conclusions                                         B
Physics results from HERA-B
                                                             HERA-B, the plan..
           Measure CP-Violation:




              Γ(B0 → f ) − Γ(B0 → f )
       Af =
              Γ(B0 → f ) + Γ(B0 → f )
                            xt 
           = sin (2δ ) sin  
                           τ 

           î        Design:
                  • Huge Interaction rate
                  • Complex di-lepton Trigger
                  • Face 4..5 overlayed interactions (LHC in 1994..)                           HERA
                  • Good PID (detect Kaons, electron/pion sepparation)
           Now: The factories do it much better..
                                                           Martin Bräuer, MPI für Kernphysik
                                                                                                 B
Physics results from HERA-B                                                                       2
                                                                                                     HERA-B
                                                 tracking




                                                                                                                   p+


                                                                         Chambers removed
                                                                                                            target
                                                                         after 2000                   VDS


                      muon         ECAL         RICH                          magnet
       20                     15                  10                            5                             0m



         • Large foreward spectrometer                   Targets used:                       ∆r = 100 µm
         • Angular coverage 15 - 250 mrad                        ∆r = 50 µm
         • Tracking and PID (µ± and e±)
         • Using the p-beam only                             +                              C               HERA
                                                         p       Ti
         • Covers x F ≡ 2 p z, c.m. s ∈ [− 0.4, 0.15 ]            500µm
                                                                                    1000µm
                                                                      Martin Bräuer, MPI für Kernphysik
                                                                                                                   B
Physics results from HERA-B                                                                                          3
                                                                    The Vertexdetector
       • Large and complex                1000 mm
         system !
       • ~ 135 000 chans.
       • Working according to                                                                           Target
         design in the year 2000
       • Roman-pot design,
         movable
       • Standalone tracking
       • Tracks used on
         trigger-level
       • Full angular
         coverage (15-250
         mRad)


        Module: double sided strip detectors,
                  50 x 70 mm2, 50µm readout
                  pitch, analog readout,                                                                 HERA
                  1024+1280 chans
        7+1 (fix) superlayer
        2 modules per superlayer per quadrant , 5° stereo - angle
                                                                    Martin Bräuer, MPI für Kernphysik
                                                                                                                 B
Physics results from HERA-B                                                                                      4
                                                        Vertexdetector Alignment




                                            n []
         Alignment determines vertex-                   4
                                                            search-window,
                                                   10              tracking                              Alle Spuren
         resolution ï Essential !                                                                        χ
                                                                                                          2
                                                                                                              Spur   < 1,75


         • time dependent                     10
                                                 3

         • 2-track-vertex-resolution reached:
                      60µm transverse,           2
                                              10
                     500µm longitudinal

                                                   10
        Principle: Linear Least Squares
        (Gauß, program: V. Blobel, H1)
        Parameter: u, α, z                         1
                                                             -1000     -500           0         500      1000
                                                                                                 uTreffer-uSpur [µm]
                              No momentum measurement in VDS,
                              not all channels perfectly working

                              ï Non-gaußian residuals !                                                       HERA

                              Solved, under control for the published data
                                                                     Martin Bräuer, MPI für Kernphysik
                                                                                                                         B
Physics results from HERA-B                                                                                                   5
                                                                                                   The Trigger
          Tracking in every bunch-crossing !
                                                                                           2 main stages:
                         Myo                      ECA
                            n   pr e-                   L pr                               - FLT (hardware)
                                     t r i gg                  e-tr                        - SLT (software)
                                             er                     igge
                                                                         r                   + tracking in VDS
                                                                                             + vertexing
                                                                             FL T




      Myo                        sear
         n                              ch
                                                                                                                  p+
                   E CA                  Trigg
                          L                    e   r-trac                           Mag
                                                            k-ch                        net
                                                                a   mbe
                                                                        rs                                        HERA
                                         Strong suppression:
                                         => FLT requires ~100% efficiency !
                                                                              Martin Bräuer, MPI für Kernphysik
                                                                                                                       B
Physics results from HERA-B                                                                                            6
                                                       How to measure with HERA-B
            Full ONLINE event processing :
                                                    trigger-tracks                                  VDS
                  tracking in VDS
                                      tracking in PC




                                                                                                             fitted tracks
                                                                                                    magnet
                                     Prolongation to TC,
                                     confirmation


                                Match                                                               RICH
                              ï momentum
                                                                        magnet
                              RICH ring ?
                              ï PID (K, p)                                                          ECAL
                                               ECAL cluster?
                                               ï PID (e)                                            muon

                              MUON-prolongation ?                                                      HERA
                              ï PID, L(µ)
                                                                Martin Bräuer, MPI für Kernphysik
                                                                                                                 B
Physics results from HERA-B                                                                                                  7
                                                                       σ bbTheory 1
         pQCD has made progress,    Heavy flavor hadroproduction, near
         problems remain:           threshold:
                                    ïsoft gluons ï large (log)
                                                      corrections
                                    ï (Sudakov) resummation
                                      σ bb @ HERA-B similar computations
                                      σ tt @ CDF/D0

                    CDF:            2 papers:
                     p p → B+ X       Bonciani et al.: NLO +
                                                       next-to-leading-log

                                      Kidonakis et al.: NNLO +
                                                        NNLL

                                                                                     HERA
                                   LHC: top-production not too far
                                   from partonic threshold ! ï ??
                                                 Martin Bräuer, MPI für Kernphysik
                                                                                       B
Physics results from HERA-B                                                             8
                                                                                       The input




                                                                                                920 GeV
                                                                                                HERA-B




         Experiment: @ 800 GeV
         E789: (p-Au)                 ( )
                              b → J/ψ µ ± X       σ (bb ) = ( 5.7 ± 1.5 ± 1.3 ) nb/nucl

         E771: (p-Si)         bb → ( µ X )( µ X ) σ (bb ) = ( 43
                                       +      −
                                                                        ± 7 ) nb/nucl
                                                                          +27
                                                                          −17
                                                                                                   HERA
         Prediction @ 920 GeV:                (12 ≤ σ(bb ) ≤ 70) nb/nucl
                                                            Martin Bräuer, MPI für Kernphysik
                                                                                                          B
Physics results from HERA-B                                                                               9
                                                                                            Theory 2
         Theoretical perspectives:                     Bonciani et al.: 23 nb @ 39,2GeV
         Assume a measurement with                      Major sources of uncertainty:
           σ (bb ) = ( 30 ± 7   ) nb/nucl               (3..12 nb/nucl each)
                                                        • b-mass (4.5 .. 5.0 GeV)
                                                        • PDF (MRSR1/2)
         Kidonakis et al. (41.6 GeV) :                  • renormalisation scale

        σ (bb ) = ( 30 ± 8 ± 10    ) nb/nucl

           kinematics                      scale
             one-particle-inklusive vs.
             pair-invariant-mass

          In addition:
          - PDF‘s
          - ambiguities in expressions
          - subleading log contributions                                                           HERA
          - higher orders (maybe)              They need differential
                                               measurements !
                                                               Martin Bräuer, MPI für Kernphysik
                                                                                                     B
Physics results from HERA-B                                                                           10
                                                                                               Methods
              Measure the cross section:
              • Semileptonic decays
                                                               All Methods possible
              • Exclusive reconstruction                       with the data from the
              • Detached vertex                                last season !

                          Used for the published analysis (limited staistics)




                   Data sample used : 450,000 µ+µ- and
                                      900,000 e+ e- candidates !


                                                                                                     HERA


                                                                 Martin Bräuer, MPI für Kernphysik
                                                                                                       B
Physics results from HERA-B                                                                             11
                                                                                 Method used
         Measure cross section for detached vertices relative to prompt cross section
         ï minimize systematics.
          1. select Np prompt pN → J / ψ X
                                       2. select NB from bb → J / ψ X

                                     NB               1
                ∆σ b b        = σr ⋅    ⋅      ∆z
                                     NP εR ⋅ εB ⋅ Br (bb → J / ψ X )
                                                          detached vertex selection efficiency
                                                                                               εB
                                                     relative detection efficiency
            3. Normalize to σ(pN → J/ψ X)                                                      εP
                  using E789/E771 scaled to x F ∈ [− 0.25, 0.15 ]

                                           Aα      E866 : α = 0.955 ± 0.005
                   σ r = σ (pN → J/ψ X ) ⋅                                                          HERA
                                           A
                   E789 + E771 : σ = (357 ± 8 stat ± 27 syst ) nb/nucl                                B
Physics results from HERA-B                                     Martin Bräuer, MPI für Kernphysik      12
                                        Trigger and Dataset in the year 2000
               5MHz interaction rate, produced with one target wire (C or Ti)

                        Muon Pretrigger                                  Electron Pretrigger
                         µ-candidates                                       e-candidates
                            Rin                                                                             Rin
                R µ pre =                                                                   R e pre =
                            185                                                                            1700
                                       First Level Trigger (hardware) :
                                      not ready, just counting pretriggers


                            R µ pre
                                  Second Level Trigger (software) :           R
                R out   =                                              R out = e pre
                          7000 2-track-trigger in main tracker and VDS        2500


                                            Online Farm (software) :
                                      full reconstruction & classification


                                                                                                              HERA
                                Data sample used : 450,000      and
                                                              µ + µ-
                                                   900,000 e+ e- candidates !
                                                                       Martin Bräuer, MPI für Kernphysik
                                                                                                                  B
Physics results from HERA-B                                                                                       13
                                                       Bremsstrahlung PID
           ECAL problems due to:

           • noise
           • too much material (2 X0)




               Use BRemsstrahlung:
                                                  ε BR (data ) = 0.34 ± 0.02 ± 0.02
                                         e±        ε BR (MC) = 0.34 ± 0.01 ± 0.01
                         ∆x
                                     γ

                                                                                            HERA

                              ECAL            magnet
                                                        Martin Bräuer, MPI für Kernphysik
                                                                                              B
Physics results from HERA-B                                                                    14
                                                                                                                        Prompt Signals
                                         J/ψ → e + e -                                                                  J/ψ → µ + µ -
                     2500
                                                    ≥0 bremsstrahlung γ   a)
                     2000                                                                         600
                     1500




                                                                               2
                                                                                                  500




                                                                               Entries/25 MeV/c
                     1000
                           500                                                                    400                                         + −
                                                                                                                                            µ µ data
                             0                                                                                                                      + −
       2




                                                     ≥1 bremsstrahlung γ b)                       300                                       Fit to µ µ data
       Entries/ 50 MeV/c




                           400                                                                                                               + + − −
                                                                                                  200                                       µ µ /µ µ data
                           200                                                                    100

                             0                                                                      0
                                                     2 bremsstrahlung γ   c)                            2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 3.8                     4
                                                                                                                + −                     2
                            80                                                                                 µ µ invariant mass (GeV/c )
                            60                                                               • reco-tracks, confirmed by trigger-tracks
                            40
                            20
                                                                                             • Likelihood cuts: µ-system & RICH
                             0                                                               • Dimuon vertex required
                                 2 2.25 2.5 2.75 3 3.25 3.5 3.75 4 4.25 4.5
                                           + −                     2
                                          e e invariant mass (GeV/c )                             µ + µ - - signal :
          Strong PID requirements:                                                                  2880 ± 60
              • E / p = 1 ± 3σ                                                                                                                      HERA
                                                                                                  e + e - - signal :
              • bremsstrahlung tagging
                                                                                                    5710 ± 380 stat ± 280 syst
                ε BR = 0.34 ± 0.02stat ± 0.02syst
                                                                                                              Martin Bräuer, MPI für Kernphysik
                                                                                                                                                          B
Physics results from HERA-B                                                                                                                                   15
                                                                                         Detached Vertex Selection
                      Identify    pA → bb → J / ψ X                                                                                             X               l+
                                              → µ +µ −
                                                   + −
                                           or → e e                                            p   +                       b                                         l-

                      Signature: long lifetime ï use
                      • impact parameter (Iw) and                                                  Iw                                      z flight ≈ 8 mm
                      • flight-distance (∆z) cuts
                                                                                                                    ∆z                                  ≈ 10 × σ z vertex
     Entries/ 10 µm




                                                        Data                               10 2                                                         Data
                                                                                                                       ∆z


                                                                               Entries/40 µm
               10 2
                                          Iw            Prompt J /ψ MC                                                                                  MC

                                                        b→ J /ψX MC                        10
               10

                                                                                               1
                      1
                                                                                                        -2   -1.5     -1 -0.5 0 0.5 1 1.5 2
                                                                                                                     + −
                          0      0.02      0.04      0.06      0.08      0.1                                        e e decay length ∆ z (cm) H E R                       A
                                   Lepton impact parameter to the wire (cm)


                                                         Optimise cuts: maximizing S MC                                               Bdata
                                                                                                                    Martin Bräuer, MPI für Kernphysik
                                                                                                                                                                          B
Physics results from HERA-B                                                                                                                                               16
                                                                                                                                      Detached Signals
                                                                                                                    Upstream spectrum                 Downstream spectrum
                                       b → J / ψ → µ +µ −
                                                                                                            4                                a)                         b)




                                                                                        2
                                                                                        Entries/100 MeV/c
                                                                                                            3
                                                               NB = 1.9 +1..5
                                                                        −
                                                                          22
                                                                                                            2

                                                                                                            1

                                                                                                            0
                                                                                                                     2.5       3    3.5     4 2.5     3             3.5      4
                                                                                                                                + −                     2
                                                                                                                               µ µ invariant mass (GeV/c )
                                                             + −
                                       b → J /ψ→ e e
                                                                                                                    Upstream spectrum                Downstream spectrum
                                                                                                                                              a)                          b)



                                                                                        2
                                                                                        Entries/100 MeV/c
                                                                                                            6
                                                               NB = 8.6 +3..9
                                                                        −3 2
                                                                                                            4
                                      4.5
       e e invariant mass (GeV/ c )
      2




                                             Upstream                Downstream
                                       4                                                                    2
                                      3.5
                                                                                                            0
                                       3                                                                        2   2.5    3     3.5 4      2 2.5 3 3.5               4   4.5
                                                                                                                                + −                     2
                                                                                                                               e e invariant mass (GeV/c )
                                      2.5                                                                                                                           HERA
      + −




                                       2
                                                                                                                                                                          B
                                        -3      -2      -1    0      1        2     3
                                                             + −
                                                             e e decay length ∆z (cm)
Physics results from HERA-B                                                                                                     Martin Bräuer, MPI für Kernphysik            17
                                                                Cross Section Measurement
          • Extrapolating to full xF
          • Combining both channels




          We get:
                     (
          σ (bb ) = 32        +14       +6
                              −12, stat −7, syst   ) nb/nucl


         Published:                                            N.Kidonakis et al. (2001) : NLO+NNLL
         Eur. Phys. J. C 26, 345-355 (2003)                    Phys.Rev. D64(2001) 114001-1

                                                               R.Bonciani et al. (2002) : NLO+NLL with latest MRST PDF
                                                               Nucl. Phys. B529 (1998)

                                                                                                                      HERA
                                Recent calculations agree well !
                                                                                  Martin Bräuer, MPI für Kernphysik
                                                                                                                        B
Physics results from HERA-B                                                                                              18
                     N(J/ψ)    52.8 k
                     M(J/ψ) 3.125 GeV
                     σ(J/ψ) 63 MeV

                      No Bremsstrahlung
                      requirement


40 % of statistics
                     N(J/ψ)    25.0 k
                     M(J/ψ) 3.113 GeV
                     σ(J/ψ) 63 MeV
                     ≥ 1 Bremsstrahlung
                     requirement
                                                        σ bb from the New Data Set
                J/ψ→e+e- : 40 % of statistics                    J/ψ→µ+µ- : 60 % of statistics
                                                                                          ∆z < - 0.5 cm
                                                                                 No upstream J/ψ

                          HERA
                              -B, pr
                                               elim !                                      !
                                       downstream
                                                                          e lim
                                                                     , pr                                  Impact
                                                                   -B Entries 740                          par. cut
                                                                 RA     Χ /ndf   2
                                                                                22.73/26
                                                            HE
                         upstream
                                                                               N(J/ψ)     40.35 ± 11.22
                                                                               M(J/ψ)     3.087 ± 0.022
                                                                               σ(J/ψ)     0.0696 ± 0.015
          ∆z/σz > 10                                                                 ∆z > 0.5 cm
          impact par. cut
          No bremsstrahlung
          requirement
                                    # J/ψ = 40 ± 12                     # J/ψ = 40 ± 11                    HERA
         2000 :                                         2000 :
         n = 8.6+3.9                                    n = 1.9 +2.2
          B     −3.2                                     B      −1.5
                                                                       Martin Bräuer, MPI für Kernphysik
                                                                                                                B
Physics results from HERA-B                                                                                       20
                                                                                        Charmonium 1

            Typical parametrisation of pA cross section                           σpA = σpN · Aα
             if α = 1 for all xF, pT    no nuclear effects

            Measure for J/ψ and χc nuclear dependence vs. xF, pT
                                                                                       K.G.Boreskov, A.B.Kaidalov hep-ph/0303033
                                                              NRQCD
                                                 χc
            Using Carbon &
                                                        total J/ψ
            Tungsten
            2-wire sample                               direct J/ψ

                                         ψ(2s)

             Input to test               R.Vogt Nucl. Phys. A700(2002)539

             different models
                                                                                                                   HERA
            χc production characteristics, nuclear dependence
               nearly unexplored
                                                                            Martin Bräuer, MPI für Kernphysik
                                                                                                                            B
Physics results from HERA-B                                                                                                   21
                                                                                            Charmonium 2
                                             xF distribution


                                                                       J/ψ              1         N J / ψ ⋅ ε C/ ψ ⋅ L C 
                                                                                                               J
                                                                   α         =                       W
                                                                                              ln  J / ψ J / ψ            
                                                                               ln( A W / A C )  N C ⋅ ε W ⋅ L W 

                                                                        Statistical errors only



                              No corrections applied !

                         xF range : [- 0.35, 0.15]


                                                                               Muon channel full statistics




                                                  •      Statistical error estimation for 2-                        HERA
                                                         wire sample (only µ-channel)

                                                                                Martin Bräuer, MPI für Kernphysik
                                                                                                                          B
Physics results from HERA-B                                                                                                   22
                                                       Charmonium Production : χc
          Fraction of J/ψ produced via χc                                       ∆M = M (J/ψ γ) – M (J/ψ)
                                                                               background subtracted
           R χc =
                     ∑ σ (χ ci )Br (χ ci → J / ψγ )                                N(χc) = 6806 ± 1058
                              σ ( J / ψ ) tot                                      M(χc) = 0.437 ± 0.004 GeV




                                                       Entries/12.5 MeV/c2
                                                                                   σ(χc) = 0.044 ± 0.008 GeV
                                                                                                      Only µ-channel
                                                                                              HE R
                                                2000                                                   A -B
                                                                                                           , pr
                                                                                                                  elim
                                                                                                                       !




                                                 √                                                       ∆M [GeV/c²]

                   Measurement 2000 based on                     First measurement of χc                           HERA
                   380 ± 74 χc                                   suppression
                 Rχc = 0.32 ± 0.06stat ± 0.04sys                 in nuclear matter possible !
                                                                              Martin Bräuer, MPI für Kernphysik
                                                                                                                           B
Physics results from HERA-B                                                                                                23
                                                   Upsilon Production : σ(pA→ Υ )
                                Υ→µ+µ-                              Υ→e+e-



                              HE R                                          HE R
                                     A -B                                            A -B
                                         , pr                                            , pr
                                                elim                                               elim
                                                     !                                                  !


                                          Y   Y´ Y´´                       Υ Υ´Υ´´



               # Υ events 35 ± 8 Width 157 MeV                 # Υ events 33 ± 10 Width 335 MeV

                                          Width : in agreement with MC

                   Existing measurements by E605, E771 contradictory
                                                                                                        HERA
                 Measurement of the Υ production cross section is feasible
                 may help to distinguish between Fermilab measurements
                                                                    Martin Bräuer, MPI für Kernphysik
                                                                                                            B
Physics results from HERA-B                                                                                 24
                                                                 Minimum Bias
         We took also a min-bias data
         sample ( 220 ⋅ 10 6 events):


         We see         J/ψ → µ + µ -
                                                    HER
                                                               A-B
                                                                   ,         pre
         ï independent cross checks                                             lim
                                                                                        !

         ï promising !

         Statistics too low for
         competetive prompt cross
         section determination !


                                                                                        HERA
                                        µ + µ - invariant mass [GeV/c]

                                                    Martin Bräuer, MPI für Kernphysik
                                                                                            B
Physics results from HERA-B                                                                 25
                                                                                   Minimum Bias

                   HER                                   Wires: C, Ti, W
                          A-B   N(D0)   162 ± 27
                   pr e
                        lim ,
                                M(D0)  1.865 GeV
                                σ(D 0) 30 ± 5 MeV          K0s              2.8 M
                            !     85 % of statistics
                                                           Λ0               620 k              ~ factor 300 to
                                                           Λ0               310 k              2000 statistics
                                                           Ξ-                 10 k
                                                           Ξ+                6.2 k
                                                           Ξ0(1530)          1.5 k
                                                           Ω-                  500
                                                           Ω+                  460
        HER
               A-B               N(D+) 82 ± 12             K*0 + K*0        1.1 M
        pr e
             lim ,               M(D+) 1.868 GeV           Φ                  63 k
                 !               σ(D+) 26 ± 4 MeV
                                   85 % of statistics
                                                        Measurements of differential cross sections,
                                                        atomic number dependence
                                                         Measurement of ratio (D+/D0)       HERA


                                                                      Martin Bräuer, MPI für Kernphysik
                                                                                                             B
Physics results from HERA-B                                                                                      26
                                                    Summary and conclusions
            • HERA-B has determined σ bb with the data-set of the year
              2000                +6
                                      (
                              σ (bb ) = 32
                              +14
                                             −12, stat −7, syst   ) nb/nucl

            • Recent calculations agree well
            • First measurement with negative xF
            • First measurement with J/ψ → e + e - and J/ψ → µ + µ - measured
              simultaneously

            The new data:
            • Large new data set
            • Promising first results
            • Understanding of the detector improved
                                                                                                                  HERA
            • Analysis ongoing

                                                                              Martin Bräuer, MPI für Kernphysik
                                                                                                                    B
Physics results from HERA-B                                                                                          27
                                                                                 Selection Cuts
              Optimise cuts: maximizing S MC                 Bdata


                                                  µ channel          e channel
                       requirement                ∆z σ z >   7 .5                ∆z > 5 mm
                                                      Iw > 45 µm                  Iw > 200 µm
                                                    Iprim > 160 µm   Min(e, trk ) > 250 µm
                                        ∆z
                              εR ⋅ εB               0.41 ± 0.01              0.44 ± 0.02
                                             MC



                        Iw          : impact parameter with respect to the wire
                        Iprim       : impact parameter with respect to the primary vertex
                        Min(e, trk) : minimum distance between electron track and
                                      any other track
                                                                                     HERA


                                                                     Martin Bräuer, MPI für Kernphysik
                                                                                                         B
Physics results from HERA-B                                                                              28
                                                                                 Systematics

                                                          statistics        ch                        syst
         external/internal sources          ch   syst%    dominated sources                           %
          σr                                eµ 11         µ+µ- bkg                                µ   +10
          BR(bb → J/ΨX )                    eµ    9       fluctuations                                -24
         trigger & detector sim. ε r        eµ    5       e + e - bkg shape                       e     7
         b production / decay               eµ    5       e + e - bkg                             e    11
         Prompt counting J/Ψ np   ( )       e     5       fluctuations
         Prompt J/Ψ MC prod. Mod.           eµ    2.5     Partial contribution                    e   13
                                                                                                  µ   +10
         A-dependence in ε R ⋅ ε   ∆z
                                        b   eµ    1.7                                                 -24
         Partial contribution               e    17
                                            µ    16

                                            Total:    +20 %
                                                                                                      HERA
                                                      -23 %

                                                              Martin Bräuer, MPI für Kernphysik
                                                                                                            B
Physics results from HERA-B                                                                                  29

				
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