Charmonium Production in 920 GeV Proton-Nucleus Interactions Presented by Wolfgang Gradl for the HERA-B The HERA-B Experiment  High rate forward spectrometer (design: up to 40 MHz interaction rate)  Angular coverage: 15 – 220 mrad in bending plane, 15 – 160 mrad in vertical plane  Multiple target wires (C, Ti, W) simultaneously in HERA’s 920 GeV proton beam = 41.6 GeV  Excellent vertexing:  z ¼ 430  m,  x,y ¼ 45  m for primary vertex  Very good particle identification (e, , , K, p) capabilities: RICH, ECAL, MUON  Hardware track trigger for lepton pairs  Online event reconstruction on 240 processor PC farm Pretriggers: ECAL clusters or hit coincidences in Muon Detector as trigger seeds (custom hardware) First Level Trigger (FLT): Track trigger in custom hardware using tracking detectors behind magnet Second Level Trigger (SLT): FLT track confirmed, search second track, extrapolation to Vertex Detector, vertex fit (PC farm) HERA-B detector: data is read out and buffered for 10  s (proton bunches cross every 96 ns, 0.5 interactions/BX) The dilepton trigger chain Fourth Level Trigger (4LT): Full online event reconstruction and classification (PC farm) Tape storage: 150 Million dilepton triggers 5 MHz 3 MHz 20 kHz 100 Hz Data Taking Period 2002/03  Running time:480 h  Dilepton trigger events150 £ 10 6  J/  rate 1,000 h -1 (both channels) N J/  = § 730 N J/  = § 550  About 300 k J/  ! ee,  collected  Mainly on C and W targets  Study of J/ ,  (2S),  c production  Investigation of x F, p T dependence  A dependence of production  Sensitive range: -0.3 · x F · 0.15 Charmonium Production Dielectron ChannelDimuon Channel J/  Production Via  c Decays  Radiative decay:  c ! J/   ! l + l -  (l = e,  )   c selection :  M ´ M(ll  ) – M(ll)  ECAL resolution does not allow separation of  c ,  c2  Published using 2000 data (based on 370 § 74 reconstructed  c in both channels):  2002/03: in total ¼ 15,000  c ! l + l -   Preliminary result for R  c using 20 % of statistics (1280  c !  +  -  reconstructed):  Results are compatible within errors  M [GeV]  M [GeV] (background subtracted)  0 Production p T dependence of polarization in J/  !  +  - : expected statistical error on J/  ! e + e - A-Dependence of J/  Production  Parameterisation:  Nuclear effects:   1  Strength of `anomalous’ J/  suppression determined by A dependence  Analysis method: use only runs with two simultaneously operated targets ) cancellation of systematic uncertainties no need to determine absolute luminosities  Preliminary results using only 25% of available statistics  Preliminary: normalize to result of E866 J/  ! e + e - J/  Differential Distributions J/  Polarization W C Stat.err §§ e§e§ Target (5-6.5)§ 5%-0.3 < x F < 0.1C, W cRangeTarget -0.5 § 0.1C, W Target J/  ! e + e - Introduction Investigation of Charmonium production:  Measurement of  (2S) production cross section   0  J/  production via feed-down from  c1,2  Differential cross sections for J/ , polarization of J/  Nuclear effects in Charmonium production:  A dependence of J/  production  Accessible kinematic range: · x F · 0.15 first measurement at negative x F possible Conclusions Part of HERA-B’s statistics of 2002/03 analysed. Preliminary results obtained for J/  production via  c,  (2S) production, J/  differential distributions. First result of A dependence of J/  production at negative x F. N J/  ¼ 177, % of statistics: N J/  ¼ 101,000  Measurement of   0 relative to J/  production:   J/  = 357 § 8 § 25 nb/nucl based on E771 and E789 results  Preliminary result using J/  ! e + e - produced on Carbon target only: