1. Simulation of a general purpose detector for the HESR project at GSI Darmstadt Conceptual Design Report: http://www.gsi.de/GSI-Future V.Hejny* for the Antiproton Physics Study Group *Institut für Kernphysik, Forschungszentrum Jülich Why experiments with antiproton beams ? High Energy Storage Ring Overview of the detector system Simulation methods (Geant4, Pluto, Root) Simulation results Future tasks

2. DPG Meeting Münster, 13.03.2002 Why antiprotons ? Strong interaction in the subnuclear regime: Quantum Chromodynamics (QCD) high energies  s << 1: perturbative QCD low energies, hadrons  s  1: non-perturbative QCD “the hadron” Open questions: quark confinement masses of strong interacting complex systems firm establishment of hybrids and glueballs … pp – annihilation: (at 1.5 – 15 GeV/c) particle – antiparticle production (qq, hyperon – antihyperon, …) strange and charm quarks interpolates between the extreme QCD limits (  s  0.3, relativistic effects small) gluonic degrees of freedom produced with high probability (ref. LEAR/CERN)

3. DPG Meeting Münster, 13.03.2002 Physics program Structure of hadrons / interaction with nuclear matter  Charmonium spectroscopyPoster HK 12.4 direct formation of all cc states, resolution given by beam  Charmed hybrids and glueballsPoster HK 12.6 high probabilty for gluonic states in pp annihilation  Charmed mesons in matterPoster HK 12.1 extension of the existing programs ( ,K) to the charm sector (D, J/ , …)  Hypernuclear physicsPoster HK 12.7 hypernuclear states, medium effects, properties of hyperons  Further options:Poster HK 12.5 CP violation in the DD system and in hyperon decays Rare decays of D-mesons

4. DPG Meeting Münster, 13.03.2002 GSI Future & HESR High Energy Storage Ring (HESR): Momentum range1.5 – 15 GeV/c Momentum spread10 -4 (with electron cooling < 8GeV/c: 10 -5 ) Beam diameter100  m Antiprotons stored in ring5 x 10 10 Luminosity (pellet target) 2 x 10 32 cm -2 s -1 Integrated luminosity10 pb -1 /day

5. DPG Meeting Münster, 13.03.2002 Detector properties Basic request:Build a modular, multi-purpose spectrometer for neutral and charged particle detection over the relevant angular (4  ?) and momentum range (<1 GeV/c up to 10 GeV/c ?). Demands: rate capability 2 x 10 7 annihilations/s particle discrimination , e, , , K, p vertex reconstruction for D, K 0 s,  (   100  m) momentum reconstruction  p/p  1 – 2 % total pp cross section  100 mb reaction cross sectionsnb range and smaller various trigger conditions(e + e - ), (  ), (  +  - ), (  ), (KK),…

6. DPG Meeting Münster, 13.03.2002 A (first) view of the detector

7. DPG Meeting Münster, 13.03.2002 Simulation scheme: Tools:ROOT for data handling and analysis http://root.cern.ch http://root.cern.ch PLUTO++ for event generation (ROOT library) http://www-hades.gsi.de/computing phase space / exp. distributions for certain reactions http://www-hades.gsi.de/computing read in by Geant4 or processed directly in ROOT Geant4for detailed detector simulations http://geant4.web.cern.ch/geant4 currently used version: 4.4.0 http://geant4.web.cern.ch/geant4 linked with ROOT to use ROOT file I/O PLUTO++ in ROOT event generation (into ROOT files) Detector simulation in Geant4 fast simulation in ROOT Analysis in ROOT direct output into ROOT files results

8. DPG Meeting Münster, 13.03.2002 Detector components (a second view): target spectrometerforward spectrometer micro vertex detector electromagnetic calorimeter DIRC: Detecting Internally Reflected Cherenkov light straw tube tracker mini drift chambers muon counter superconductive coil iron yoke

9. DPG Meeting Münster, 13.03.2002 Detector components: MVD 7.2 mio. barrel pixels 50 x 300 μm 2 mio. forward pixels 100 x 150 μm 50 mm 200 mm Micro Vertex Detector: (as implemented in Geant4) Number of layers5 in barrel, 5 in endcap Thickness (single layer) 200  m Thickness (5 layers)1.25% of X 0 Resolution   z  25 … 100  m

10. DPG Meeting Münster, 13.03.2002 Detector components: MVD Demanded resolution:   100  m Simulation results:  D0) = 51  m  Z0) = 82  m track y x z D0 Z0 Matches resolution for D, K 0 s,  identification !

11. DPG Meeting Münster, 13.03.2002 Detector components: STT MVD DIRC STT Straw Tube Tracker: Number of double layers15 Skew angle of layer 1 and 150°0° Skew angle of layers 2-142°-3° Straw tube wall thickness 26  m Wire thickness 20  m Gas90:10 He and C 4 H 10 Length150 cm Tube diameters (1-5, 6-10, 11-15)4, 6, 8 mm Total number of tubes8734 Transverse resolution 150  m Longitudinal resolution1 mm example event: pp    4K

12. DPG Meeting Münster, 13.03.2002 Detector components: MDC Number of cathode planes2 chambers x 3 layers x 2 planes Orientation of wire planes0°, 60°, 120° Signal wire thickness 25  m Field wire thickness 100  m Cell size1 cm x 1cm, i.e. 7000 channels Gas90:10 He and C 4 H 10 Mini Drift Chamber: Resolution: 150  m

13. DPG Meeting Münster, 13.03.2002 Overall performance Track and momentum resolution: Vertex resolution 50 – 80  m Momentum resolution (TS)1 – 2 % pp  J/  +  (  s = 4.4 GeV/c 2 ): J/    +  -   +-  +-  (J/  = 35 MeV/c 2  (  = 3.8 MeV/c 2

14. DPG Meeting Münster, 13.03.2002 Detector components: DIRC Existing DIRC: BaBar @ SLAC DIRC: Detecting Internally Reflected Cherenkov light working scheme: Angle coverage22° - 140° Quartz thickness and length1.7 cm / 150 cm SensorsGas chambers with multi-pad readout particle light cone focal plane with light sensors quartz slab

15. DPG Meeting Münster, 13.03.2002 Detector components: DIRC Particle identification: reconstruction of light cone momentum reconstruction used: a)determination of the orientation of the light cone b)calculation of particle mass from  and p K eff.  miss-id. reaction pp   at  s = 3.6 GeV/c 2 “the real picture”

16. DPG Meeting Münster, 13.03.2002 Detector components: EMC Electromagnetic calorimeter: Detector materialPbWO 4 Photo sensorsAvalanche Photo Diodes Crystal size  35 x 35 x 150 mm 3 (i.e 1.5 x 1.5 R M 2 x 17 X 0 ) Decay constant< 20 ns Energy resolution 1.54 % /  E[GeV] + 0.3 % Time resolution   130 ps Total number of crystals7150 Solid angle coverage 96 % x 4  barrel backward endcap forward endcap

17. DPG Meeting Münster, 13.03.2002 Detector components: EMC Invariant mass resolution: e/  particle discrimination: Reaction: pp  J/  +  (  s = 4.4 GeV/c 2 ) m(  )= 0.501 GeV/c 2  (  ) = 0.020 GeV/c 2

18. DPG Meeting Münster, 13.03.2002 Detector components: Muon counter Moun counter: PositionOutside of iron yoke Covered angle  30° - 80°,  = 360° Bar thickness2 cm Detector performance:  identification  misidentification

19. DPG Meeting Münster, 13.03.2002 Overall performance Reconstruction of a secondary vertex: pp   +  - K 0 s K 0 s  3  + 3  - Total acceptance: (geometry x detection eff. x reconstruction) pp  J/  + X (  s = 4.4 GeV/c 2 ) J/    +  - J/   e + e - suppressing of combinatorical background by momentum conservation: primary vertex secondary vertex     (K 0 s  = 3 MeV/c 2

20. DPG Meeting Münster, 13.03.2002 Summary and Outlook Current status: A general purpose detector for antiproton physics has to be designed for the GSI Future Project Simulations are performed in a framework of Geant4, ROOT and PLUTO++ The solenoid part (target spectrometer) is nearly fully implemented Results show that the current design meets the requirements Future tasks: Completion of the detector implementation in Geant4 (forward spectrometer) Setting up an easy-to-handle analysis framework for the simulation results Intensive background simulations: Total annihilation cross section is 200 mb, typical reaction cross section is in the order of nb  for each valid event  10 8 events have to be simulated to prove background suppression  hardly to be handled by Geant4  fully ROOT based, fast simulation is in preparation Workshop on experiments with antiprotons at the GSI future facility April 5 to 6, 2002 at GSI (further information: http://www-wnt.gsi.de/pbar)

21. DPG Meeting Münster, 13.03.2002 Antiproton Physics Study Group T. Barnes 8, D. Bettoni 6, R. Calabrese 6, W. Cassing 5, M. Düren 5, S. Ganzuhr 1, A. Gillitzer 7, O. Hartmann 2, V. Hejny 7, P. Kienle 9, H. Koch 1, W. Kühn 5, U. Lynen 2, R. Meier 11, V. Metag 5, P. Moskal 7, H. Orth 2, S. Paul 9, K. Peters 1, J. Pochodzalla 10, J. Ritman 5, M. Sapozhnikov 3, L. Schmitt 9, C. Schwarz 2, K. Seth 4, N. Vlassov 3, W. Weise 9, U. Wiedner 12 1 Experimentalphysik I, Bochum 2 GSI, Darmstadt 3 JINR, Dubna 4 Northwestern University, Evanston 5 Universität Gießen 6 INFN, Ferrara 7 Institut für Kernphysik, FZ Jülich 8 University of Tennessee, Knoxville 9 Technische Universität München 10 Institut für Kernphysik, Mainz 11 Physikalisches Institut, Tübingen 12 ISV, Uppsala