1. Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions Ulrich Husemann for the HERA-B Collaboration Experimentelle Teilchenphysik, Universität Siegen 6 th International Conference on Hyperons, Charm & Beauty Hadrons Illinois Institute of Technology, Chicago, IL, June 27 - July 3, 2004

2. U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions2 Outline of the Talk HERA-B detector and trigger systems Charmonium production Open charm production Summary

3. U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions3 Detector & Trigger

4. U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions4 10 m The HERA-B Detector Magnet Muon Detector 4 layers of gas pixel chambers (inner) and MWPC with cathode pad readout (outer), pad-coincidence pretrigger 0 m20 m Top View 920 GeV/c Protons Inner / Outer Tracker 7 layers of GEM-MSGCs (inner) and honeycomb drift chambers (outer) Wire Target 2 stations, 4 wires each (C, Ti, W) Silicon Vertex Detector 8 double-layers of double-sided Si-microstrips RICH C 4 F 10 radiator, multianode PMT focal plane ECAL W/Pb-scintillator sampling calorimeter, shashlik readout, cluster pretrigger

5. U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions5 The Dilepton Trigger HERA-B detector: data is read out and buffered for 10  s (proton bunches cross every 96 ns, 0.5 interactions/BX) Pretriggers: ECAL cluster or hit coincidence in muon detector as trigger seed (custom hardware) 5 MHz First Level Trigger (FLT): Track trigger in hardware using tracking detectors behind magnet, seeding by pretriggers 3 MHz Second Level Trigger (SLT): FLT tracking confirmed, extrapolation to vertex detector, vertex fit (PC farm) 20 kHz 100 Hz

6. U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions6 Data-taking period: October 2002–February 2003 Dilepton trigger: require  2 electrons or muons –Trigger performance: >1,000 J/  per hour –Sample for charmonium studies: 300,000 J/  10,000  c 3,500  (2S) –Study of beauty production  see talk by H. Wahlberg, B3.8 Minimum bias trigger: minimum activity in RICH/ECAL –200 million events recorded –Strangeness and hyperon production –Pentaquark searches  see talk by A. Sbrizzi, ST.3 –Open charm production Data Sample 2002/2003

7. U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions7 Dilepton Spectrum: Muon Channel Approx. 177,000 events Mass: 3095 MeV/c 2 Width: 44 MeV/c 2 J  Approx. 3,000 events Mass: 3674 MeV/c 2 Width: 53 MeV/c 2  2S  Low-mass region:   High-mass region:  1S   2S/3S 

8. U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions8 Charmonium Production

9. U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions9 J/  Production Cross Section J/  e + e – /  +  –  signals observed in minimum bias data Determination of J/  cross section without trigger bias (systematic effects currenty under study) J/  e + e – J/  +  –

10. U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions10 J/  Differential Cross Section: p T 80% of e+e– sample Parametrization:  Broad p T coverage, good agreement of electron and muon channel

11. U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions11 J/  Differential Cross Section: x F 10% of e+e– sample Large acceptance for negative x F (fractional longitudinal momentum) Parametrization: Work on systematics ongoing

12. U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions12 J/  A-Dependence Test of charmonium production models in nuclear matter (nonrelativistic QCD + initial/final state interactions in nucleus) Parametrization: –  < 1: charmonium suppression by nuclear effects –HERA-B: extract  from runs with two target wires simultaneously (carbon: A=12, tungsten: A=184) I. Ratio of J/  yields: fits to invariant mass spectra II. Ratio of luminosities: intercalibration of target wires III. Ratio of efficiencies: detailed detector/trigger simulation 3 ingredients of A-dependence measurement:

13. U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions13 J/  A-Dependence Previous result of FNAL E866 extended to x F = –0.3 Result from 10% of full  +  – sample, statistical uncertainties only Two different combinations of carbon and tungsten wires (different acceptances): consistent results Work on systematics ongoing Preliminary Sample I Sample II Preliminary

14. U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions14 Measure  (2S) cross section relative to J/   reduce systematic uncertainties  J    (2S) = 0.72 (MC) Preliminary result (electrons, 30% of full statistics): Muon channel: compatible results R = 0.13 ± 0.02 (stat.)  (2S) Production Preliminary

15. U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions15 Published result of 2000 data-taking (370±74  c ): I. Abt et al., Phys. Lett. B561 (2003) 61  c Production Test of charmonium production models: fraction R(  c ) of J/  from radiative decays  c  J/    +  –  R(  c )=0.32 ±0.06(stat.)±0.04(syst.)

16. U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions16 Preliminary result (15% of  +  – statistics,1,300  c ):  compatible with 2000 results, systematic studies ongoing R(  c )=0.21±0.05(stat.) Subtraction of combinatorial background (event mixing) R(  c ): Analysis in 2002/2003 Signal found in mass difference M(J/   ) – M(J/  )

17. U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions17 Open Charm Production

18. U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions18 Open Charm Production Open charm signals in minimum bias data (charge-conjugated channels included): D0K +D0K + Events:189 ± 20 M [MeV/c 2 ]:1863 ± 3  [MeV/c 2 ]:25 ± 3 D +  K   +  + Events:98 ±12 M [MeV/c 2 ]:1866 ± 2  [MeV/c 2 ]:15 ± 2 D *+  D 0  +  K   +  + Events:43 ± 8  M [MeV/c 2 ]:145.9 ± 0.2  [MeV/c 2 ]:0.89 ± 0.15

19. U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions19 Open Charm Production Preliminary

20. U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions20 New Limit on BR(D 0  +   ) Search for flavor-changing neutral current decay D 0  +   (branching fraction enhanced in some SUSY models) 3 events in signal region: Currently best upper limit I. Abt et al., hep-ex/0405059, to be published in Phys. Lett. B Previous limit by CDF: BR(D 0  +   ) < 2.5  10 -6 (90% CL) D. Acosta et al., Phys. Rev. D68 (2003) 091101 BR(D 0  +   ) < 2.0  10 -6 (90% CL) 18 events 6 events3 evt

21. U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions21 Summary & Outlook HERA-B has finished data-taking Analysis of 2002/2003 data in progress Charmonium production: –Production cross sections and differential distributions –A-dependence of J/  production: HERA-B covers x F <0 –Production ratios:  (2S) to J/  fraction of J/  from  c Open charm production: –D meson production cross sections and ratios: D 0, D ±, D *± –New limit for FCNC decay: D 0  +   Outlook: –First results of 2002/2003 run to be published soon –Stay tuned – more interesting results to come Thanks to: HERA-B charmonium & open charm working groups

22. U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions22 Dilepton Spectrum: Electron Channel Approx. 101,000 events Mass: 3136 MeV/c 2 Width: 64 MeV/c 2 J    2S 

23. U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions23 Why Charmonium Production? Test of current framework for charmonium production models: nonrelativistic QCD (perturbative expansion in relative quark velocities) Modification of models via nuclear effects –Initial state effects, e.g. shadowing, energy loss –Final state effects, e.g. absorption in nuclear matter –Parametrization: power law with exponent  =  (x F,p T )  is measure of A-depencence (A: target atomic mass)  < 1: charmonium suppression by nuclear effects (anomalous suppression: signature for quark-gluon plasma)

24. U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions24 A-Dependence: Theory Prediction 2: BCKT (Reggeon-based) K.G. Boreskov, A.B. Kaidalov, JETP Lett. 77 (2003) 599 HERA-B range all J/  Prediction 1: NRQCD + nuclear absorption R. Vogt, Nucl. Phys. A700 (2002) 539 HERA-B range  (2S) all J/  cc

25. U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions25 A-Dependence: HERA-B‘s Contribution Measurements in proton-nucleus scattering (Fermilab E866/NuSea) as a function of x F M.J. Leitch et al., Phys. Rev. Lett. 84 (2000) 3256 HERA-B HERA-B: Extend kinematic range to x F <-0.3 Triggering 2 channels simultaneously: e,  2 materials simultaneously (C, W)  better control of systematic effects