6 th International Conference on Hyperons Charm Beauty

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

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

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

The HERA-B Detector Muon Detector 4 layers of gas pixel chambers (inner) and MWPC with cathode pad readout (outer), pad-coincidence pretrigger Top View Inner / Outer Tracker 7 layers of GEM-MSGCs (inner) and honeycomb drift chambers (outer) Wire Target 2 stations, 4 wires each (C, Ti, W) 920 Ge. V/c Protons ECAL W/Pb-scintillator sampling calorimeter, 20 m shashlik readout, cluster pretrigger RICH C 4 F 10 radiator, multianode PMT 10 m focal plane Magnet Silicon Vertex Detector 8 double-layers of double-sided Si-microstrips 0 m U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 Ge. V Proton-Nucleus Collisions 4

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) 5 MHz Pretriggers: ECAL cluster or hit coincidence in muon detector as trigger seed (custom hardware) 3 MHz First Level Trigger (FLT): Track trigger in hardware using tracking detectors behind magnet, seeding by pretriggers 20 k. Hz Second Level Trigger (SLT): FLT tracking confirmed, extrapolation to vertex detector, vertex fit (PC farm) 100 Hz U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 Ge. V Proton-Nucleus Collisions 5

Data Sample 2002/2003 Data-taking period: October 2002–February 2003 n Dilepton trigger: require 2 electrons or muons n – Trigger performance: >1, 000 J/ per hour – Sample for charmonium studies: • 300, 000 J/ • 10, 000 c • 3, 500 (2 S) – Study of beauty production see talk by H. Wahlberg, B 3. 8 n 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 U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 Ge. V Proton-Nucleus Collisions 6

Dilepton Spectrum: Muon Channel High-mass region: J/ Low-mass region: f r/w Approx. 3, 000 events (2 S/3 S) Mass: 3674 Me. V/c 2 Width: 53 Me. V/c 2 Approx. 177, 000 events Mass: 3095 Me. V/c 2 Width: 44 Me. V/c 2 (1 S) (2 S) U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 Ge. V Proton-Nucleus Collisions 7

Charmonium Production U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 Ge. V Proton-Nucleus Collisions 8

J/ Production Cross Section n J/ e+e– / + – signals observed in minimum bias data J/ e+e– n J/ + – Determination of J/ cross section without trigger bias (systematic effects currently under study) U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 Ge. V Proton-Nucleus Collisions 9

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

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

J/ A-Dependence Test of charmonium production models in nuclear matter (nonrelativistic QCD + initial/final state interactions in nucleus) n Parametrization: n – < 1: charmonium suppression by nuclear effects – HERA-B: extract from runs with two target wires simultaneously (carbon: A=12, tungsten: A=184) n 3 ingredients of A-dependence measurement: 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 U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 Ge. V Proton-Nucleus Collisions 12

J/ A-Dependence Preliminary Sample II Previous result of FNAL E 866 extended to x. F = – 0. 3 n Result from 10% of full + – sample, statistical uncertainties only n Two different combinations of carbon and tungsten wires (different acceptances): consistent results n Work on systematics ongoing n U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 Ge. V Proton-Nucleus Collisions 13

(2 S) Production Preliminary Measure (2 S) cross section relative to J/ reduce systematic uncertainties n e. J/ /e (2 S)= 0. 72 (MC) n Preliminary result (electrons, 30% of full statistics): n R = 0. 13 ± 0. 02 (stat. ) n Muon channel: compatible results U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 Ge. V Proton-Nucleus Collisions 14

cc Production n Test of charmonium production models: fraction R( c) of J/ from radiative decays c J/ m+ m– Published result of 2000 data -taking (370± 74 c): R( c)=0. 32 ± 0. 06(stat. )± 0. 04(syst. ) I. Abt et al. , Phys. Lett. B 561 (2003) 61 U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 Ge. V Proton-Nucleus Collisions 15

R(cc): Analysis in 2002/2003 n Signal found in mass difference M(J/ ) – M(J/ ) Subtraction of combinatorial background (event mixing) n Preliminary result (15% of + – statistics, 1, 300 c): R( c)=0. 21± 0. 05(stat. ) compatible with 2000 results, systematic studies ongoing U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 Ge. V Proton-Nucleus Collisions 16

Open Charm Production U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 Ge. V Proton-Nucleus Collisions 17

Open Charm Production Open charm signals in minimum bias data (charge-conjugated channels included): D 0 K + Events: 189 ± 20 M [Me. V/c 2]: 1863 ± 3 [Me. V/c 2]: 25 ± 3 D+ K + + Events: 98 ± 12 M [Me. V/c 2]: 1866 ± 2 [Me. V/c 2]: 15 ± 2 D*+ D 0 + K + + Events: 43 ± 8 M [Me. V/c 2]: 145. 9 ± 0. 2 [Me. V/c 2]: 0. 89 ± 0. 15 U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 Ge. V Proton-Nucleus Collisions 18

Open Charm Production Preliminary U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 Ge. V Proton-Nucleus Collisions 19

New Limit on BR(D 0 + ) 18 events 3 evt 6 events n Search for flavor-changing neutral current decay D 0 + (branching fraction enhanced in some SUSY models) n 3 events in signal region: BR(D 0 + ) < 2. 0 10 -6 (90% CL) Currently best upper limit I. Abt et al. , hep-ex/0405059, to be published in Phys. Lett. B n Previous limit by CDF: BR(D 0 + ) < 2. 5 10 -6 (90% CL) D. Acosta et al. , Phys. Rev. D 68 (2003) 091101 U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 Ge. V Proton-Nucleus Collisions 20

Summary & Outlook HERA-B has finished data-taking n Analysis of 2002/2003 data in progress n Charmonium production: n – Production cross sections and differential distributions – A-dependence of J/ production: HERA-B covers x. F<0 – Production ratios: (2 S) to J/ , fraction of J/ from c n Open charm production: – D meson production cross sections and ratios: D 0, D±, D*± – New limit for FCNC decay: D 0 + n 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 U. Husemann, Univ. Siegen: Open and Hidden Charm Production in 920 Ge. V Proton-Nucleus Collisions 21