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					 HERA-B results



Università and INFN – Bologna

From the HERA-B Collaboration




           HERA-B results       1
                              13 Nations
    HERA-B:                   30 Institutes           150 physicists
              IHEP, Beijing              Norway
      China                                            U. Oslo
              U. Tsinghua
                                                       LIP, U. Coimbra
   Denmark    NBI, Copenhagen           Portugal       LIP, U. Lisbon
                                                       ITEP, Moscow
              U. Humboldt, Berlin      Russia          JINR, Dubna
              U. Dortmund
              DESY                   Slovenia
              MPI Heidelberg                           J.F. Inst, Ljubljani
   Germany    U. Heidelberg
              U. Mannheim
                                        Spain          U. Barcelona
              MPI Munich
              U. Rostock          Switzerland          U. Zurich
              U. Siegen
              DESY Zeuthen            Ukraine          INR, Kiev

              INFN, U. Bologna                         U. Texas, Austin
      Italy
                                                       U. Cincinnati
              U. Utrecht                        USA    Wayne State U.
Netherlands   NIKHEF                                   U. Houston
                                                       U. Calif, Los Angeles
                               HERA-B results                         2
              The HERA-B Detector
       Muon Detector
      4 layers of gas pixel      Inner / Outer Tracker                Top View
     chambers (inner) and        7 layers of GEM-MSGCs
    MWPC with cathode pad         (inner) and honeycomb        Wire Target
         readout (outer),          drift chambers (outer)   2 stations, 4 wires
   pad-coincidence pretrigger                                each (C, Ti, W)


                                                                         920 GeV/c
                                                                          Protons


e+/e- beam
                                                                   Silicon Vertex
                                                      Magnet          Detector
                                                                   8 double-layers of
                ECAL                  RICH                            double-sided
                                  C4F10 radiator,                    Si-microstrips
           W/Pb-scintillator     multianode PMT
        20sampling shashlik
           m                         10 plane
                                   focal m                          0m
          calorimeter, cluster
               pretrigger
                                  HERA-B results                              3
had to face LHC equivalent
particle flux 10 ears in                      Si
advance.
                                                   gas
       exploring a new
      regime of radiation
      load, particle flux,
      event rates...


detectors               At forefront
trigger system          of technology
DAQ                          HERA-B results              4
          The HERA-B detector
 p-Nucleus interactions at 920 GeV
                                                 S=41.6 GeV
BX crossing rate: 10 MHz  Up to 4•107 interactions/s (~5ev/bx)
Very sophisticated and challenging detector.
Large central acceptance ( 5 > lab > 2 )
Capability to reconstruct the full event
Very good particle ID for (e, , , K, p)
High resolution vertexing
Target: 8 wires in the p-beam halo
  5 materials: C, Ti, Al, Pd, W                         184W

Double wire configuration for                12C
A-Dependence Measurements: C+W
Online event reconstruction
Very selective multilevel trigger                 48Ti

(hardware + software) J/  μμ/ee                            z [cm]



  Suitable for P-Nucleus interaction studies
                              HERA-B results                     5
Electromagnetic Calorimeter (ECAL)
               INFN contribution (Bologna)




Main Italian responsibilities:
 readout and pretrigger electronics
 Second Level Trigger and reconstruction codes
 Detector calibration and maintenance
                           HERA-B results         6
              Trigger & DAQ System
Multilevel trigger scheme based on Kalman filter.


5 (10) MHz      Pretrigger/Level 1
  (<12 s)
                 (rejection ~250)

 20 KHz               Level 2
 (5-10 ms)       (rejection. ~200)


100 Hz       Full online reconstruction
 (~1s)           and logging to tape



Two PC-Linux farms used in L2 and for the offline
reconstruction.        HERA-B results               7
             Main data samples
Data taking finished in 2003.


•150 M di-lepton trigger events (e+e-/μ+μ- triggers)
    300 000 J/ψ (>1000 per hour)
    15 000 c1+ c2                               Electrons
       5 000 ψ(2S)
                                              ~ 108,000 J/

• 210 M minimum bias events                   σ = 64 MeV/c2

   1000 ev/s >1TB/day
                                    /
                                                ~ 1600 (2S)
• 35 M hard photon events

• 60 M “glueball” trigger events
Dilepton spectrum: Muon Channel

                                      High-mass region:
   Low-mass region:
                             J/
                                         Approx. (2S/3S)
                                                 3,500 events
        /                              Mass: 3674 MeV/c2
                                         Width: 53 MeV/c2
                     
   Approx. 177,000 events                (1S)
   Mass: 3095 MeV/c2
   Width: 44 MeV/c2
                                      (2s)



                     HERA-B results                             9
                 Physics topics
Main physics topics addressed:
 FCNC D0  μμ Br limit
                                                 Di-lepton trigger
 bb cross section                         J/
  production                                      e+ e-
 J/ production                       (2s)        + -
   J/: pT distribution                     C
   J/: xF distribution                    D0
   J/: A-dependence                       bb
 (2s) production                   (1-3s)        MB data
 c/J/ production ratio              D0           K()
 Open charm production
                          HERA-B results                     10
 Pentaquark production
          New Limit on BR(D0+)
                                                                W+
                                                  c                       μ+
        18 events   3 evt   6 events                                           BR from
                                                        d,s,b        νμ
                                                                          μ-   SM: ~10-19
                                                  u
                                                                W-
                                               • Search for flavor-changing
                                                 neutral current decay D0+
                                                 (branching fraction enhanced in
                                                 some MSSM models ~10-7)
                                               • 3 events in signal region:

                                                        BR(D0+) < 2.010-6
                                                             (90% CL)
                                               Phys.Lett.B596:173-183,2004
Current limits by :
    •CDF: BR(D0+) < 2.510-6 (90% CL) Phys. Rev. D68 (2003) 091101
    •BaBar: BR(D0+) < 1.310-6 (90% CL) hep-ex/0408023
                                       HERA-B results                               11
        σ(bb): inclusive b production
    B Meson has a long life time ( ~ 9 mm at HERA-B kinematics)
               ~ 0.5 mm dilepton vertex resolution
   J/ from a B decay will be detached from primary interaction
                                               upstream   downstream
    pA  bb X                                                    ℓ+
          b  J/ψ Y  e+e-/+- Y                          Δz          J/ψ
                                                 p
                                                            b                 ℓ-
    Analysis cuts:
    - Decay lenght (Δz)                                   IW            Y
    - Impact parameter

Normalization on the
inclusive prompt J/ cross
section.
 Systematic error
minimization
                              HERA-B results                             12
                  open b production
• C,W,Ti targets
• Full statistics
• Unbinned likelihood fit

   ( )
  bb
              0.027  0.004  0.005
 ( J / )

20% sys. error under investigation,
main contribution:
Br(bbJ/X) = 2.320.20%


Lifetime:

 = (1.41 ± 0.16)ps

                               HERA-B results   13
                      Cross section
Cross section obtained by using the fit based on NRQCD of J/ψ cross
sections .
                                                                 Previous HERA-B result of year

   ( )
  bb  14.9  2.2  2.4 nb/nucleon
                                                                 2000 (~ 10 ev)
                                                                 [Eur. Phys. J. C26, 345 (2003)]:
                                                                    s (bb) = 32-+12-+7 nb/N
                                                                                 14 6
    Phys. Rev. D73 (2006) 052005
• Theoretical uncertainties:                                                         N. Kidonakis et al.




                                      σ(bb) (nb/nucleon)
                                                           102
                                                                    HERA-B
   – b quark mass 4.5 - 5 GeV                                       E789
   – At NLO, scale ()                                              E771
     dependence                                            10

• Previous measurements do not
  agree between each other
• Agreement with the previous                              1
  HERA-B result (1.5 σ)
                                                                           R. Bonciani et al.
                                                            400      500     600    700    800   900       1000
                                                                                   Proton energy (GeV)
                              HERA-B results                                                     14
                 Upsilon production
       30.87.4stat                       pN  + X,             +-, e+e-
                                                 d
                                Br (  l l  )       ( ) | y 0
                                                  dy                   n  J /  1
Drell-Yan                                                                   
                                  Br ( J /   l l  )   J /      nJ /     yeff
   Comb. BG                         NLO calculation inside CEM (hep-ph/0311048)


            M(+-) (GeV/c2)


       7514stat      ee                                         NA3       E605
                                                                             E605
                                                                                     CERN
                                                                   FNAL              CCOR
                                                                   FNAL      E772    HERA-B
                                                                   FNAL      E771
                                                                   FNAL      R-108




                                       d                          m        Craigie
                                Br                ( s )   o exp   o      parametrization
                                        dy    y 0                    s
             M(e+e-) (GeV/c2)   HERA-B results                                         15
                 J/ψ production cross section
                                ( A)
                            N
s   ( A)
    J/y    =                    J/y ® e+ e- / m+ m-                                                         W
                                                      ( A)        ( A)
               Br( J / y ® e e / m m ) ×
                                 + -
                                        L  + -
                                                             ×e




                                                                            σ(pAJ/ψ)
                                             inclusive                                            Ti




                                                                                   [μb]
                     μ+μ-                   measurement
                  100 ± 12
                                     used MB data to minimize                             C
                                        trigger systematics
                                    for each target material                                                     A
                                    (A = 12 [C], 48 [Ti], 184 [W])

                                                                         p-p                HERA-B          PHENIX
                                                                         p-A
               μμ mass
               [GeV/c2]

s   pN   (J/y ) = (663 ± 74 stat ± 46syst )nb/nucl
                                                                         IHEP             experimenta
                                                                                             l data
     Good agreement with the fit of J/ψ + ψ′                                               sometimes
     cross sections and ψ′/ψ production ratios                                            inconsistent
     (29 results in all) in the context of NLO                             WA39
               NRQCD (F. Maltoni) HERA-B results                         CERN-                preliminary   16
                                                                           PS
          J/ψ Differential Distribution: pT
Electron channel: compared with p-A results (√s=38.8 GeV) agreement with
muon channel in all distributions.
       1 ds                                                                       <pT> grows
              [GeV-2/c2]                                                        logarithmically
A     s dpT 2
                                                                                    with A:
197




                                                             <pT> [GeV/c]
                           E789 (Au)
184
 48
 28                                    HERA-B (W)

 12
  9
                                          HERA-B (Ti)
                                        E771 (Si)
             E672/E706 (Be)                                                            Si Ti    W Au
                                                                               Be C
                                       HERA-B (C)
                                                                            d pT
ds                                              pT [GeV/c]                           = 0.021 ± 0.003
     µ é + (35p ×pT < pT >) ù                                               d ln A
                           2 - 6
   2
       1 256
       ê                    ú
dpT    ë                    û
                                         HERA-B results                                        17
     J/ Differential distribution: xF
Electron channel: compared with p-A results (√s=38.8 GeV) agreement with
muon channel in all distributions.
                                                     Fitting curves:
                                                      d s / d xF µ [(1 - x1 )(1 - x2 )]k /(x1 + x2 )
                 E789 (Au)
                                                                     1
                                                      with x 1 , 2 =   (x 2 + 4 m 2 y /s ± x F
                                                                          F        J/          )
                                                                     2
                             E672/E706 (Be)

                                     E789
                                    (Be, Cu)                C
                 E771 (Si)

                                                                  Ti
        HERA-B (C-W)


                                                                           W



      first data produced
         at negative xF
                                    HERA-B results                                        18
                    J/ polarization
Measured in different reference systems (CS, GJ, HCM) and wrt pT and xF
                                                                Interaction & p-
                                                    Exp.                                
        GJ               Preliminary:                              momentum

                         [-0.3,0.0] ±0.1            E379       p-Fe @ 400 GeV      0.16 ± 0.08
                                                  E672/E706    p-Be @ 530 GeV      0.01 ± 0.15
                          Same range as           E672/E706    p-Be @ 800 GeV      -0.11 ± 0.15
                          previous                  E771       p-Si @ 800 GeV      -0.09 ± 0.12
                          experiments                                              [+0.1 : -0.5]
                                                    E866       p-Cu @ 800 GeV
                                                                                    xf [0.3:0.9]


   pT                     xF                                   angle perpendicular to 

                                                                     Hint for  > 0




                                                            No experimental results
                                                           important to study also 
        Also studied by CDF but at larger pT
                                 HERA-B results                                        19
            J/ A-Dependence
  • Test of charmonium production models in nuclear
    matter (nonrelativistic QCD + initial/final state
    interactions in nucleus)         A ;   N /  L
                                     pA   pN




• Previous result of FNAL E866 extended to xF = –0.35
• Result from full +– sample, statistical uncertainties
  only, similar results for e +e -
                           HERA-B results                20
                             (2S) Production
                                                                                            (1.63 ± 0.07)% C
      BR( (2S)     
                          )   (2S)     N (2S) J/ 
 R                                                                                  =   (1.99 ± 0.24)% Ti
       BR(J /      
                          )   J/       NJ/   (2S)
                                                                                            (1.62 ± 0.10)% W

                                                                        E444                 NA38,    E789
• Measure (2S) cross                                                NA38 E705               NA50 &      HERA-B c




                                            B′σ(ψ′)/Bσ(J/ψ) (%)
                                                                        E331                  NA51       HERA-B ti
  section relative to J/                                            p-A               E288              HERA-B w
  reduce systematic                                                                                  E771

    uncertainties                                                      18                        12
                                                                                   6           9 27       197
                                                                        4                  9 2
• No dependence wrt A                                                                        1
                                                                                                  64
                                                                                                    108 28 12
                                                                          2 12                       184     184
  and cms energy                                                          3
• Competitive                                                             8

  measurements
                                                                          12
                                                                                                               s   [GeV ]
                                                                  HERA-B results                               21
        (2S)differential distributions
                                                                 BJ/y ®                       í J/y
Fraction of J/ψ from ψ′:                       Ry ¢ = r y ¢ ´                l+ l-            ï
                                                                                              ï       p +p -
                                                                                     ×By ¢®   ï
                                                                                              ï J/y   p 0p 0   = (7.0 ± 0.2 ± 0.4 BRs )%
                                                                 By ¢®     l+ l-
                                                                                              ì
                                                                                              ï J/y
                                                                                              ï
                                                                                              ï J/y
                                                                                                      h
                                                                                              ï
                                                                                              î       p0

Constraint on the double ratio (test of lepton universality)
  e+ e-      +
               By ¢® e+ e-
                  -
                           By ¢® m+ m-
 ry ¢   m m
         ry ¢            =                                        = 1.00 ± 0.08± 0.04
                             BJ/y ®   e+ e-
                                                BJ/y ®   m+ m-                          current PDG avg.: 1.03 ± 0.12

                                              HERA-B                                  E771
                                                                                      NA50                              NRQCD (p-p)
                                              E789
           B ¢ds (y ¢)                                              B ¢ds (y ¢)
          Bds ( J /y )                                             Bds ( J /y )




                                                   pT                                                                      xF
            HERA-B measurements extend the range of the previous
                                     or better
            results with comparable HERA-B results precision                                                                  22
                              c Production                                                  background: mixed events

Test of charmonium production models:




                                                                       Entries (10 MeV/c2)
                                                                                                         Muon channel
fraction R(c) of J/ from radiative decays
c J/  μ+ μ– 

                      c ,i  BR( c,i  J/ )
               2
                                                      N c  J /
  R(  )      i 1
                                                          
                              J /                   NJ /  c  
     c
     R(c)




                                      Average




                                                    HERA-B results                                       M(J/ ) – M(J/)
                                                                                                                23
                                 ECMS
              Pentaquark Searches
                     Phys. Rev. Lett.93:212003,2004

First negative result based on high statistics and performed
on two different states.                     wire
                                                          K-(us) or (uds)
Searched pentaquark states:
Θ+(1530, uudds) → pK0 (or nK+)                        p     + (uudds)

Ξ  (ddssu) → Ξ π (or Σ K) → Λππ                              K0
              and charge c.
                                                              p

MB data sample (~210M evts, 3 nuclear targets C, Ti, W) used to:
 search for the reported pentaquark signals
 provide upper limits on particle yield ratios (vs Λ(1520) and Ξ0(1530))
 possibly determine physical quantities (width, spin, parity, charge) of
                                states (p-K
pentaquarks for different finalHERA-B results 0, -)               24
                                 +,-- signals
                           pK0s mass                   mass                           NA49
 Counts




                                                    Counts
                                                                                   HERA-B
B d/dy b/C




                                                  B d/dy b/C
                     UL(95%)
                                                                               UL(95%)
                                                                 

               1.4    1.475 1.55 1.625      1.7
                         mass GeV/c2
                     UL(95%)Bd/dy|y=0 =                          UL(95%)Bd/dy|y=0 =
                         4-16 b/N                               2.5 b/N @ 1862 MeV/c2
                     @ 1521-1555 MeV/c2
                                                                     -- / - < 3/B %
                 + / (1520) < 3 – 12 %                          -- / (1530)0 < 4/B %
                               Phys. Rev. Lett. 93 (2004) 212003
                                             HERA-B results                              25
                      Open charm production: signals K                                                                                                                           -
                                                                                                                  p+
                      p                   K-                                               p                                                            p D *+ D 0
                                  0                                                                D   +               K-                                                             p+
                              D
                                                              p+                                                       p+
                          N                                                                    N                                                          N                     p+

                                         D0+D0                                                                          D±                                       D*±           49 ± 10




                                                                                                                                 entries/(0.5 MeV/c2)
                                           194 ± 20                                                               92 ± 11

                                                                     entries/(10 MeV/c2)
entries/(10 MeV/c2)




                                                                                                                                                              | m( K p ) - m( D0 )|< 50MeV
                                                                                                                                                              | m( K p ) - m( D0 )|> 50MeV

                                      Kπ inv. mass                                                     Kππ inv. mass [GeV/c2]                                  m(Kππ)-m(Kπ) [GeV/c2]
                                       [GeV/c2]
                                                                                                   D0                                                         D+
                                               dN/dz [a.u.]




                                                                                               cτ = 125 ± 21 μm                                            cτ = 292 ± 38 μm
     agreement with
     PDG values                                                                                            preliminary

                                                                                   HERA-B
                                                                   proper decay length [μm] results                         proper decay length [μm]                                 26
                         Open charm production: cross section
                          preliminary                        -0.1 <   xF < 0.05     full xF range
                     σ(D0) [μb/nucl]                         21.4 ±   3.2 ± 3.6  56.3 ± 8.5 ± 9.5
                     σ(D+) [μb/nucl]                         11.5 ±   1.7 ± 2.2 30.2 ± 4.5 ± 5.8
For Isospin symmetry
 and feeddown BRs,   σ(D*+) [μb/nucl]                        10.0 ±   1.9 ± 1.4 27.8 ± 5.2 ± 3.9
      expected       σ(D+)/σ(D0)                                       0.54 ± 0.11 ± 0.14
                     σ(D*+)/σ(D0)                                      0.49 ± 0.12 ± 0.10


s INCL ( D± )/ s INCL ( D0 ) = 0.326 ± 0.003 s INCL ( D*± )/ s INCL ( D0 ) = 0.497 ± 0.001
                 violated by about a factor 2
                                                                   avg. = 0.43 ± 0.09
Important test for QCD




                             avg. = 0.61 ± 0.08
                             D±/D0                                 D*±/D0


                                                  HERA-B
                                                   prel.                              HERA-B prel.
                                                                                  ud
                                            ud
                                        √                                     √
                                                  HERA-B results                             27

				
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