Physics from HERA-B Torsten Zeuner PRC open session 7th May 2003 Universität Siegen PRC open session 7th May 2003

Data taking 2002/03 Data taking 30. October 2002 – 03. March 2003 35 % ~ 35 % running time delivered of which ~ 70 % used for data taking ~ 150 · 106 dilepton triggered events ~ 210 · 106 minimum bias events achieved J/ψ rates : 1200 – 1400 J/ψ per hour 30 - 40 J/ψ per hour (2000)

J/ψ - Statistics J/ψ→µ+µ- : full statistics J/ψ→e+e- : 40 % of statistics J/ψ→µ+µ- : full statistics N(J/ψ) 52.8 k M(J/ψ) 3.125 GeV σ(J/ψ) 63 MeV N J/ψ 166 k M J/ψ 3.095 GeV σ J/ψ 45 MeV Nψ(2s) 2.7 k Mψ(2s) 3.672 GeV σψ(2s) 53 MeV No Bremsstrahlung requirement Entries/30 MeV/c² N(J/ψ) 25.0 k M(J/ψ) 3.113 GeV σ(J/ψ) 63 MeV ≥ 1 Bremsstrahlung requirement μ+μ- invariant mass [GeV/c²]

Analysis in Progress Improve pN→bbX cross section measurement higher statistics in inclusive analysis : b→J/ψX (J/ψ→ee/μμ) exclusive recon. of b decays (B±→J/ψK±, B0→J/ψK±π±, B→J/ψKs, B→J/ψKK) Understand double semileptonic b decays: bb→µµX Atomic number dependence of charmonium production in pN extend existing Fermilab measurements of J/ψ, ψ´ to negative xF measurement of atomic number dependence of χc Minimum Bias physics Open charm production Strangeness production in nuclear matter Λ polarization Measurement of pA→ Υ cross section (ee/μμ) Upper limit on Br(D0→μ+μ-) Direct photons ...

bb Cross Section Measurement Inclusive reaction pA → bb X, with bb  J/ X → (e+ e- / µ+ µ-) X Select b  J/ X via detached J/ψ vertices IW l+ J/ B z X l- upstream | downstream Normalization to prompt J/ψ (pA  J/X) Minimize systematic errors

Detached J/ψ Analysis J/ψ→e+e- J/ψ→µ+µ- # J/ψ = 40 ± 12 Δz/σz > 10 impact par. cut No bremsstrahlung requirement (40 % of statistics) Preliminary downstream 2000 : upstream # J/ψ = 40 ± 12 J/ψ→µ+µ- Δz < - 0.5 cm Δz > 0.5 cm Impact par. cut (60 % of statistics) Entries 740 Χ2/ndf 22.73/26 N(J/ψ) 40.35 ± 11.22 M(J/ψ) 3.087 ± 0.022 σ(J/ψ) 0.0696 ± 0.0154 Preliminary 2000 : No upstream J/ψ # J/ψ = 40 ± 11

Charmonium Production 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 Using Carbon & Tungsten 2-wire sample NRQCD K.G.Boreskov, A.B.Kaidalov hep-ph/0303033 χc total J/ψ direct J/ψ ψ(2s) Input to test different models R.Vogt Nucl. Phys. A700(2002)539 χc production characteristics, nuclear dependence nearly unexplored

Charmonium Production xF distribution Statistical errors only No corrections applied ! xF range : [- 0.35, 0.15] Statistical error estimation for 2-wire sample (only μ-channel) Muon channel full statistics e-channel increases statistics up to factor 2 (depending on particle ID cuts)

Charmonium Production : χc Fraction of J/ψ produced via χc ΔM = M (J/ψ γ) – M (J/ψ) background subtracted Entries/12.5 MeV/c2 ΔM [GeV/c²] N(χc) = 6806 ± 1058 M(χc) = 0.437 ± 0.004 GeV σ(χc) = 0.044 ± 0.008 GeV 2000 √ Only µ-channel Preliminary Measurement 2000 based on 380 ± 74 χc First measurement of χc suppression in nuclear matter possible ! Rχc = 0.32 ± 0.06stat ± 0.04sys

Upsilon Production : σ(pA→ Υ ) Υ→μ+μ- Υ→e+e- Y Y´ Y´´ Υ Υ´ Υ´´ Preliminary Existing measurements by E605, E771 contradictory Preliminary # Υ events 35 ± 8 Width 157 MeV # Υ events 33 ± 10 Width 335 MeV Width : in agreement with MC Measurement of the Υ production cross section is feasible may help to distinguish between Fermilab measurements

Minimum Bias Data sample Open charm signals ~210·106 events recorded on Carbon, Tungsten and Titanium wire N(D0) 162 ± 27 M(D0) 1.865 GeV σ(D0) 30 ± 5 MeV K0s 2.8 M 85 % of statistics 0 620 k ~ factor 300 to 2000 statistics 0 310 k - 10 k + 6.2 k Preliminary 0(1530) 1.5 k - 500 N(D+) 82 ± 12 M(D+) 1.868 GeV σ(D+) 26 ± 4 MeV + 460 K*0 + K*0 1.1 M  63 k 85 % of statistics Measurements of differential cross sections, atomic number dependence Measurement of ratio (D+/D0)

Expect preliminary results for summer conferences. Summary HERA-B detector & trigger in good shape Data taking : 30.October 2002 – 3.March 2003 1200-1400 J/ψ per hour, 70% of available beam time used ~ 300,000 triggered J/ψ (e+e-/μ+μ-) ~ 210·106 Minimum bias events Analysis of 2002/03 data in progress Quality of recorded data looks good, first preliminary results promising Expect preliminary results for summer conferences.