M.Mevius Open and hidden beauty production in 920 GeV proton –nucleus collisions at HERA-B M.Mevius DESY

M.Mevius Outline the HERA-B experiment open b production upsilon production conclusions

M.Mevius The HERA-B Detector

M.Mevius Data Sample Data taking is finished in 2003; analysis is in progress additional: 210 M minimum bias events 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 VDS vertex reconstruction online event reconstruction 150 M dilepton trigger events J/  (>1000 per hour)  c  (2S)

M.Mevius Dilepton spectra ~ 1600 Long Tracks (Vertex Detector + Tracking System) PID:  likelihood, E/p Dilepton Vertex Probability > 1% J/  acceptance: < x F < 0.15 muon channel ~ 108,000 J/  → ee σ = 64 MeV/c2 //  J/   (2S) electron channelmuon channel ~ 108,000 J/   ee σ = 64 MeV/c2 //  J/   (2S) electron channel ~ 177,000 J/    σ = 44 MeV/c 2 ~ 3000  (2S) ~ 1600

M.Mevius open b production Theoretical uncertainties: –b quark mass GeV –At NLO, scale (  ) dependence Previous measurements do not agree between each other

M.Mevius pn  bb + X b(b)  B  J/  + X J/       ; e + e - open b production Measurement relative to direct J/  production to minimize trigger/reconstruction uncertainties  R = relative efficiency  1 B selection eff. from MC

M.Mevius open b production B Selection: (30-45% Efficiency) Lepton impact to the wire Distance J/  to wire 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

M.Mevius open b production Vertex z resolution ~ 500 μm Good agreement between data and MC simulation good separation between direct and detached J/  Cuts optimized simultaneously Background: bb and cc simultaneous semileptonic decays Combinatorial Prompt J/ 

M.Mevius open b production C,W,Ti targets Unbinned likelihood fit preliminary 20% sys. error under investigation main contribution: Br(bb  J/  X) = 2.32  0.20%

M.Mevius J/  cross section E771/E789 : scaled to HERA-B cms energy  (J/  )=357 ± 2 ± 36 nb/nucleon E771/E789 HERA-B measurement on min. bias data ongoing using E771/E789 result: preliminary

M.Mevius upsilon production HERA-B  s = 41.6 GeV E772 (A=2) E605 (A=64) 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]) Theoretical prediction Hadronization: Possible nuclear suppression ?

M.Mevius upsilon production pA  + X   μ +μ- ; e+e- Measurement relative to prompt J/  –Less sensitive to systematic effects Prompt J/  cross section from E771 and E789

M.Mevius upsilon production 25% W + 75 % C (targets) Mass resolution between 140 and 160 MeV/c 2 Background: Drell-Yan: shape estimated from MC  (1S) /  (2S) /  (3S) relative production fixed to E605 results Random combinatorial: estimated from like sign pairs in data 8

M.Mevius upsilon production 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 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

M.Mevius upsilon production Not used in fit  Modified Craigie parameterization to include nuclear suppression (parameter  ) Data compatible with no nuclear suppression:  = 0.99  0.05

M.Mevius HERA-B has finished data taking preliminary results: –  (bb) : using:  (J/  )=357±2±36 nb/nucleon –  production: Conclusions

M.Mevius model dependence 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 )

M.Mevius 92% of J/  are produced in our x F range J/  from b decays kinematics