Open and Hidden Charm production in 920 GeV Proton-Nucleus Collisions Presented by Marko Stari for the Hera-B collaboration The Hera-B detector High rate forward spectrometer (1 40 MHz) Angular coverage : 15 220 mrad in bending plane, 15 160 mrad in vertical plane Interaction of 920 GeV/c protons with nuclei of target wires (s = 41.6 GeV) at e-p storage ring HERA Acceptance in mid-rapidity region Eight wires in halo of HERA proton beam Wire materials with atomic number A from 12 (C) to 184 (W) Designed for high interaction rates Radiation hard detectors Particle identification (e, , , K, p) Hardware track-trigger for lepton pairs High speed digital links for trigger data transmission On-line event reconstruction with PC-farm Abstract HERA-B is a fixed-targed multi-particle spectrometer experiment at the 920 GeV proton beam at DESY. The collected data sample from the 2002/2003 HERA run includes 200 million interactions recorded with a minimum bias trigger and 150 million event taken with a dilepton trigger. Clean samples of D 0 K - +, D + K - + +, D *+ D 0 +, J/ + - and J/ e + e - from the minimum bias sample have been reconstructed. Preliminary results on the total cross sections are presented. Data sample Data taking: November 2002 March 2003 Interaction trigger: - hits in RICH or energy in ECAL - logging rates: 1000Hz (1.7 Tb/day) 182 million events three target materials: C, Ti, W TargetAEventsL [b -1 ] C (b1) M280.7 C (i2) M97.5 Ti (b2) M32.4 W (i1) Open charm D + K - + + N=9211 Data analysis at least one primary vertex found identification of K and in RICH good secondary vertex secondary vertex of D 0 (D + ) is detached: - distance significance z/ z > 6(10) - impact parameters of tracks b/ b > 4 D meson comes from primary b/ b < 3 for D*+: m(K,) within 50MeV of D 0 mass Efficiency Monte Carlo: PYTHIA FRITIOF 7.02 efficiency for D 0 : 0.6% main losses: - det. acceptance (10%) - detached vertex (10%) kinematic range: < x F < 0.05 Cross-section per nucleon Preliminary results Cross sections per nucleon ( = 1 assumed) Production ratios pN [b/N] 0.1 0.7 GeV/c good dilepton vertex Efficiency PYTHIA FRITIOF visible range in y: < y < visible fraction: 63% efficiency: 33% ( + - ) 25% (e + e - ) Preliminary results Both channels combined Visible cross sections per nucleus Differential at y=0 ( = 0.96 assumed) d pN /dy = 380 42 28 nb/N Total ( = 0.96 assumed) pN = 643 71 48 nb/N Target pA [b/nucleus] C3.91 0.70 0.27 Ti16.30 5.57 1.10 W69.60 10.8 4.7 D 0 K - + D *+ D 0 + (K - + ) + N=4910 N=19420