July Hernan Wahlberg, BEACH041 Open and Hidden Beauty in 920 GeV Proton-Nucleus Collisions Hernan Wahlberg Utrecht University/NIKHEF For HERA-B Collaboration

July Hernan Wahlberg, BEACH042 Outline HERA-B detector Reference prompt J/  sample for beauty analysis  ( ) production cross section Open cross section Summary

July Hernan Wahlberg, BEACH043 Hera-B Detector

July Hernan Wahlberg, BEACH044 Reference Prompt J/  Sample Di-Muon total sample: Approx. 177,000 J/  events Width: 44 MeV/c 2  (2S) J/  (  ) Di-Electron total sample: Approx. 108,000 J/  events Width: 64 MeV/c 2  (2S) J/  (ee) Long Tracks (Vertex Detector + Tracking System) PID:  likelihood, E/p Dilepton Vertex Probability > 1% J/  acceptance: < x F < 0.15

July Hernan Wahlberg, BEACH045  : Motivation Theoretical prediction – Hadronization: Possible nuclear suppression ? HERA-B  s = 41.6 GeV Several measurements available but unclear situation at √s ~ 40GeV HERA-B has good coverage in the central region of collisions ( x F ~ [-0.35,0.15]) E772 (A=2) E605 (A=64)

July Hernan Wahlberg, BEACH046  : Method Measurement relative to prompt J/  –Less sensitive to systematic effects Prompt J/  cross section from E771 and E789 pA  + X      - ; e + e -

July Hernan Wahlberg, BEACH047  : Signal 25% W + 75 % C (targets) Mass resolution between 140 and 160 MeV/c 2 Background: –Random combinatorial: estimated by like sign pairs of real data –Drell-Yan: shape estimated from MC  (1S) /  (2S) /  (3S) relative production fixed to E605 results

July Hernan Wahlberg, BEACH048  : Preliminary Results Both channels are compatible Extrapolation to √S = 38.8 GeV yields: Br d  /dy  y=0 = 2.4 ± 0.9 pb/n –compatible with E605 –(more than 1  ) below E772 and E771 Events Br d  /dy  y=0 +-+- 33 ± 73.9 ± 1.1 pb/n e+e-e+e- 31 ± ± 1.2 pb/n both3.4 ± 0.8 pb/n

July Hernan Wahlberg, BEACH049  : Global Situation Modified Craigie parameterization to include nuclear suppression (parameter  Data compatible with no nuclear suppression:  = 0.99  0.05 Not used in fit   s (GeV)

July Hernan Wahlberg, BEACH0410 B: Motivation Theoretical uncertainties: –b quark mass GeV –At NLO, scale (  ) dependence Previous measurements do not agree

July Hernan Wahlberg, BEACH0411 pA  bb + X b(b)  B  J/  + Y J/       ; e + e - B: Principle of the Measurement

July Hernan Wahlberg, BEACH0412 B: Principle of the Measurement 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 Only needed: count detached J/  Measurement relative to prompt J/  Prompt J/  cross section from E771 and E789

July Hernan Wahlberg, BEACH0413 B: Detached Scheme P P B Selection: (30-45% Efficiency) Lepton impact to the wire Lepton closest distance of approach to primary Distance J/  to wire

July Hernan Wahlberg, BEACH0414 B: Real Data vs. MC Vertex z resolution ~ 500  m Good agreement between real data and MC simulation

July Hernan Wahlberg, BEACH0415 B: Signal Carbon + Tungsten targets 35% of total sample Cuts optimized simultaneously Background: –bb and cc simultaneous semileptonic decays –Combinatorial –Prompt J/  Unbinned likelihood fit

July Hernan Wahlberg, BEACH0416 B: Sample Cross Check

July Hernan Wahlberg, BEACH0417 Only statistical errors Good compatibility of two channels 1.3  lower than HERA– B (2000) B: Preliminary Result

July Hernan Wahlberg, BEACH0418 B: Ongoing studies – Simultaneous semileptonic decays – Search of exclusive decays – Lifetime measurement

July Hernan Wahlberg, BEACH0419 Conclusions Events observed in hidden and open beauty in the data sample Preliminary  cross section measurement: 3.4 ± 0.8 pb/n –in agreement with E605 Global fit to  data consistent with no nuclear suppression Preliminary bb cross section measurement (35% of the total statistics) –The complete HERA-B sample will be significantly larger than previous fixed target experiments

July Hernan Wahlberg, BEACH0420 Back-up slides

July Hernan Wahlberg, BEACH0421 Essential bibliography P.NASON, QCD at High Energy, Proc. Of the XX Int. Symp. on Lepton and Photon Interactions at High Energies, hep-ph/ P.NASON et al., Adv. Ser. Direct. High Energy Phys. 15(1998), 609 H1 Coll. T.Sloan et al., Proc. QCD 2001 Conf., Moriond, March ZEUS Coll. J.Breitweg et al., Eur.Phys.J.C18(2001) L3 Coll. M.Acciarri et al., Phys.Lett.B503(2001) 10 OPAL Coll. OPAL Phys.Note PN455, August 29,2001 N. Kidonakis et al., Phys.Rev. D64 (2001) D.M.Jansen et al., Phys.Rev.Lett.74 (1995)3118 T.Alexopoulos et al., Phys.Rev.Lett.82 (1999) 41 R. Bonciani et al., Nucl.Phys.B529 (1998) 424

July Hernan Wahlberg, BEACH0422 Detector characteristics (I)  Large acceptance: mrad in x (bending plane), mrad in y (vertical plane)  Target – up to 8 wires inserted into the halo of 920 GeV proton beam (C, Ti)  VDS – Vertex Detector System. Dilepton vertex resolutions:  z  600  m,  x,y  70  m  Dipole Magnet- field integral 2.13 Tm  OTR – Outer Tracker. Honeycomb drift cells; wire pitch 5/10 mm; spatial hit resolution  350  m; Backward hemisfere in CM (negative x F ) World largerst honeycomb tracker: 1000 modules, channels  ITR – Inner Tracker: MicroStrip Gas Chambers, pitch 100  m, resolution 100  m; Forward hemisfere in CM (positive x F ) World largerst (gas) micro pattern tracker

July Hernan Wahlberg, BEACH0423 Detector characteristics (II)  RICH – Ring Imaging Cherenkov Hodoscope C 4 F 10 radiator gas, 2 planes of PMT 4  separation: e/  p  [3.4, 15] GeV/c,  /K p  [12,54] GeV/c  ECAL – Electromagnetic CALorimeter – Sandwich sampling calorimeter (“Shashlik”); Pb and W as converter; 3 regions  MUON detector – 4 tracking stations; Gas pixel chambers, Proportional tube chambers, some with segmented cathodes  DAQ system – High bandwidth, high trigger and logging rates  TRIGGER. - Pretriggers on ECAL & MUON seeds - FLT hardware based on ITR/OTR - SLT software trigger; Tracking+Vertexing; linux farm with 240 nodes  Event reconstruction; on-line, linux farm with 200 nodes

July Hernan Wahlberg, BEACH0424 b production model systematics Changing PDFs from MRST to CTEQ b quark mass from 4.5 to 5.0 GeV/c 2 QCD renormalization scale  from 0.5  o to 2  o Fragmentation functions –Peterson form with  from to –Kartvelishvili form with   from 12.4 to 15.0 from to 2.0 GeV 2 Fraction of b-baryons produced in the b-hadronization process from 0 to 12%  ±1.5%  ±1%  ±2%  ±3%  ±1%  ±2% Default model: MRST PDF, Peterson FF  =0.006 Total: ±5% Studied variations:Sys cont. to  (bb )

July Hernan Wahlberg, BEACH0425 J/  from b decays kinematics 92% of J/  are produced in our x F range