1. August 25 2005Hernan Wahlberg, HADRON051/26 Open and Hidden Beauty in 920 GeV Proton-Nucleus Collisions Hernan Wahlberg Utrecht University/NIKHEF For the HERA-B Collaboration

2. August 25 2005Hernan Wahlberg, HADRON052/26 Outline HERA-B detector Reference prompt J/  sample for beauty analysis Open cross section  ( ) production cross section Summary

3. August 25 2005Hernan Wahlberg, HADRON053/26 HERA-B Detector (I)

4. August 25 2005Hernan Wahlberg, HADRON054/26 HERA-B Detector (II) Fixed target detector at p ring HERA, DESY Proton beam at 920 GeV/c (√s = 41.6 GeV) Interaction rate ~ 5 MHz Wire targets (different materials: C,W,Ti) in proton halo Multiple trigger level (Hardware + Software) for lepton pairs High resolution vertexing (~ 500  m-longitudinal) Very good particle ID for e, , , K and p

5. August 25 2005Hernan Wahlberg, HADRON055/26 Data Sample HERA-B has finished data taking (March 2003) Dilepton trigger Pretriggers: high E T ECAL clusters, MUON hits FLT (hardware trigger): track finding behind magnet SLT (software trigger): track finding behind magnet and in silicon detector + vertex reconstruction 165 M dilepton triggered events ≈ 300.000 J/Ψ (>1000 per hour to tape) 3 target wires of different materials Carbon (A=12, ≈ 64% of total statistics) Titanium (A=48, ≈ 9%) Tungsten (A=184, ≈ 27%)

6. August 25 2005Hernan Wahlberg, HADRON056/26 Reference Prompt J/  Sample J/  : 148200±500  ’: 2600±120 J/  : 103800±1000  ’: 1700±160 Long tracks (vertex detector + tracking system) PID:  likelihood, E/p Dilepton vertex probability > 1% J/ ψ acceptance: -0.35 < x F < 0.15

7. August 25 2005Hernan Wahlberg, HADRON057/26 Outline HERA-B detector Reference prompt J/  sample for beauty analysis Open cross section  ( ) production cross section Summary

8. August 25 2005Hernan Wahlberg, HADRON058/26 B: Motivation Theoretical uncertainties: b quark mass 4.5 - 5 GeV Production near energy threshold. At NLO, scale (  ) dependence. Need to go beyond NLO Previous measurements: Poor statistical precision Incompatible HERA-B 2002 measurement

9. August 25 2005Hernan Wahlberg, HADRON059/26 B: Selection Method B Selection: (~ 40% Efficiency) Lepton impact to the wire Distance J/  to wire pA  bb + X b(b)  B  J/  + X J/       ; e + e -

10. August 25 2005Hernan Wahlberg, HADRON0510/26 B: Principle of 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 to count detached J/  Measurement relative to direct J/  production to minimize trigger/reconstruction uncertainties  R = relative efficiency  1 B selection efficiency from MC

11. August 25 2005Hernan Wahlberg, HADRON0511/26 B: Data and MC Samples Good agreement between data and MC simulation Good separation between direct and detached J/ 

12. August 25 2005Hernan Wahlberg, HADRON0512/26 B: Detached J/  (muons) Detachment cuts (on significance) optimized blindly and simultaneously: Δz > 9 σ I w l > 2.6 σ I w J/Ψ < 9σ UpstreamDownstream 46.2 +8.6 -7.9 -0.1±1.4 Upstream from target: unphysical region Downstream from target: signal region Unbinned likelihood fit Background: Combinatorial B doublesemileptonic No prompt J/ 

13. August 25 2005Hernan Wahlberg, HADRON0513/26 B: Detached J/  (electrons) Detachment cuts (on significance) optimized blindly and simultaneously : Δz > 10 σ I w l > 3.0 σ I w J/Ψ < 12σ Upstream from target: unphysical region Downstream from target: signal region Unbinned likelihood fit Background: Combinatorial B doublesemileptonic No prompt J/  UpstreamDownstream 36.9 +8.5 -7.8 -4.2±1.9

14. August 25 2005Hernan Wahlberg, HADRON0514/26 B: Sample Confirmation (I) Confirmation of B flavor: Long lived candidates around J/ψ mass B lifetime compatible with expectations 1.54 ps (PDG)  = 1.39 ± 0.19 ps

15. August 25 2005Hernan Wahlberg, HADRON0515/26 B: Sample Confirmation (II) Search for additional tracks in a common vertex ( J/  +h ± ) Relax detachment cuts Partially independent sample Higher purity but lower stat R Δσ = (4.3±1.0)x10 -2 compatible with main result (see next slide) Some fully reconstructed final state events Ongoing study based on double semileptonic bb decay sample 22 ± 5

16. August 25 2005Hernan Wahlberg, HADRON0516/26 B: Results (I) e and μ channels are partially independent Results agree well within errors μ+μ-μ+μ- e+e-e+e- μ + μ - & e + e - R Δσ (x10 -2 ) in HERA-B acceptance 3.01 ± 0.57 stat 3.60 ± 0.79 stat 3.2 ± 0.5 stat Good control of systematics

17. August 25 2005Hernan Wahlberg, HADRON0517/26 B: Results (II) σ J/Ψ = (352 ± 2 ± 26) nb/n (average E789-E771) Weighted average with previous HERA-B measurement (I Abt et al., Eur. Phys. J. C26 (2003) 345) Cross section in full x F range:

18. August 25 2005Hernan Wahlberg, HADRON0518/26 B: Results (III) Ongoing study suggests ~40% higher σ(J/ψ) and consequently σ( ) Result compatible with lower limit of theoretical predictions Compatible with E789

19. August 25 2005Hernan Wahlberg, HADRON0519/26 Outline HERA-B detector Reference prompt J/  sample for beauty analysis Open cross section  ( ) production cross section Summary

20. August 25 2005Hernan Wahlberg, HADRON0520/26  : Motivation Test quarkonium production models Possible nuclear suppression ? 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]) HERA-B  s = 41.6 GeV E772 (A=2) E605 (A=64)

21. August 25 2005Hernan Wahlberg, HADRON0521/26  : Method pA  + X      - ; e + e - Measurement relative to prompt J/  Less sensitive to systematic effects Prompt J/  cross section from E771 and E789

22. August 25 2005Hernan Wahlberg, HADRON0522/26  : Signal 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 30.8±7.4 75±14   +-  +-   e+e-  e+e-

23. August 25 2005Hernan Wahlberg, HADRON0523/26  : Preliminary Results EventsBr d  /dy  y=0 +-+- 30.8 ± 7.43.0 ± 0.7 stat ± 0.6 stat pb/n e+e-e+e- 75 ± 144.7 ± 0.9 stat ± 1.0 sys pb/n Both3.5 ± 0.8 pb/n Both channels are compatible Extrapolation to √s = 38.8 GeV yields: Br d  /dy  y=0 = 2.3 ± 0.5 stat ± 0.5 sys pb/n compatible with E605 (more than 1  ) below E772 and E771 Based on σ J/Ψ = (352 ± 2 ± 26) nb/n (average E789-E771)

24. August 25 2005Hernan Wahlberg, HADRON0524/26  : Global Situation  Modified Craigie parameterization to include nuclear suppression (parameter  Data compatible with no nuclear suppression:  = 0.96  0.05

25. August 25 2005Hernan Wahlberg, HADRON0525/26 Conclusions (I): B cross section HERA-B measured (2000+2004) R σ = (2.8±0.4±0.3)x10 -2 Lifetime of candidates in agreement with expectations Compatibility between different channels The complete HERA-B sample (~90 events) is significantly larger than previous fixed target experiments Based on σ J/Ψ = (352 ± 2 ± 26) nb/n (average E789-E771) Ongoing fit of existing experimental results on σ(J/  ) with COM parametrisation to provide absolute bb cross section

26. August 25 2005Hernan Wahlberg, HADRON0526/26 Conclusions (II):  cross section Preliminary  cross section measurement 3.5 ± 0.8 pb/n I n agreement with E605 Global fit to  data consistent with no nuclear suppression

27. August 25 2005Hernan Wahlberg, HADRON0527/26 Backup Slides

28. August 25 2005Hernan Wahlberg, HADRON0528/26 P.NASON, QCD at High Energy, Proc. Of the XX Int. Symp. on Lepton and Photon Interactions at High Energies, hep-ph/0111024 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 2001. 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) 114001-1 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 BIBLIOGRAPHY

29. August 25 2005Hernan Wahlberg, HADRON0529/26 J/  cross section E771/E789 : scaled to HERA-B cms energy  (J/  )=352 ± 2 ± 26 nb/nucleon E771/E789 HERA-B measurement on min. bias data ongoing HERA–B Preliminary

30. August 25 2005Hernan Wahlberg, HADRON0530/26 Detector characteristics (I)  Large acceptance: 15-220 mrad in x (bending plane), 15-160 mrad in y (vertical plane)  Target – up to 8 wires inserted into the halo of 920 GeV proton beam (C, Ti, W)  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 hemisphere in CM (negative x F ) World largerst honeycomb tracker: 1000 modules, 115000 channels  ITR – Inner Tracker: MicroStrip Gas Chambers, pitch 100  m, resolution 100  m; Forward hemisphere in CM (positive x F ) Not used in this analysis (stability issues)

31. August 25 2005Hernan Wahlberg, HADRON0531/26 Detector characteristics (II)  RICH – Ring Imaging Cherenkov Detector 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

32. August 25 2005Hernan Wahlberg, HADRON0532/26 MUON AND ELECTRON CHANNEL: RELATIVE X-SECTION RESULTS Channel  ee TargetCTiWC W Atomic weight 1247.87183.841247.87183.84 npnp 91850±3008080±10045380±20067100±7004800±20032400±600 n bb 27.8±6.33.0±2.115.5±4.517.8 +5.8 -5.2 0.9±1.018.4 +6.2 -5.5 <εRεΔz><εRεΔz>0.390(4)0.389(11)0.396(5)0.359(7)0.416(21)0.394(13)  0.96 Br(bb → J/Ψ X) 2.32±0.20 R Δσ A (x10 -2 )3.32±0.784.2±2.93.8±1.23.3±1.01.9±2.36.4±2.1 R Δσ (x10 -2 )3.01±0.573.60±0.79

33. August 25 2005Hernan Wahlberg, HADRON0533/26 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 0.002 to 0.008 Kartvelishvili form with   from 12.4 to 15.0 from 0.125 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 )

34. August 25 2005Hernan Wahlberg, HADRON0534/26 J/  from b decays kinematics 92% of J/  are produced in our x F range

35. August 25 2005Hernan Wahlberg, HADRON0535/26  : Theory (preliminary) Theoretical prediction: NLO + (NNLO+NNNLL) Uncertainties: b mass Renormalization scale  Compatible with Modified Craigie parameterisation HERA-B preliminary

36. August 25 2005Hernan Wahlberg, HADRON0536/26