1. Open and Hidden Charm production in 920 GeV Proton-Nucleus Collisions Presented by Marko Starič (marko.staric@ijs.si) 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, µ, π, 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 - π +, D + → K - π + π +, D *+ → D 0 π +, J/ψ →μ + μ - and J/ψ →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 [μb -1 ] C (b1)12.0168.8 M280.7 C (i2)12.0120.5 M97.5 Ti (b2)47.8724.7 M32.4 W (i1)183.867.638.2 Open charm D + → K - π + π + N=92±11 Data analysis at least one primary vertex found identification of K and π in RICH good secondary vertex secondary vertex of D 0 (D + ) is detached: - distance significance Δz/σ z > 6(10) - impact parameters of tracks b/σ b > 4 D meson comes from primary b/σ b < 3 for D*+: m(K,π) within ±50MeV of D 0 mass Efficiency Monte Carlo: PYTHIA 5.7 + FRITIOF 7.02 efficiency for D 0 : 0.6% main losses: - det. acceptance (10%) - detached vertex (10%) kinematic range: -0.10 < x F < 0.05 Cross-section per nucleon Preliminary results Cross sections per nucleon (α = 1 assumed) Production ratios σ pN [μb/N] 0.1<x F <0.05total D0D0 21.4 ± 3.2 ± 3.656.3 ± 8.5 ± 9.5 D+D+ 11.5 ± 1.7 ± 2.230.2 ± 4.5 ± 5.8 D *+ 10.0 ± 1.9 ± 1.427.8 ± 5.2 ± 3.9 ratio D + /D 0 0.54 ± 0.11 ± 0.14 D *+ /D 0 0.49 ± 0.12 ± 0.10 Hidden charm J/ψ → μ + μ - N=100±12 J/ψ → e + e - N=57±13 Data analysis identification of μ in MUON identification of e in ECAL p T > 0.7 GeV/c good dilepton vertex Efficiency PYTHIA 5.7 + FRITIOF visible range in y: -1.25 < y < +0.35 visible fraction: 63% efficiency: 33% (μ + μ - ) 25% (e + e - ) Preliminary results Both channels combined Visible cross sections per nucleus Differential at y=0 (α = 0.96 assumed) dσ pN /dy = 380 ± 42 ± 28 nb/N Total (α = 0.96 assumed) σ pN = 643 ± 71 ± 48 nb/N TargetΔσ pA [μb/nucleus] C3.91 ± 0.70 ± 0.27 Ti16.30 ± 5.57 ± 1.10 W69.60 ± 10.8 ± 4.7 D 0 → K - π + D *+ → D 0 π + → (K - π + ) π + N=49±10 N=194±20