The CBM experiment - exploring the QCD phase diagram at high net baryon densities -

1. The CBM experiment- exploring the QCD phase diagram at high net baryon densities - Claudia Höhne, GSI Darmstadt CBM collaboration • The CBM experiment • physics case, observables • detector layout • feasibility studies and R&D of detector components

2. Physics case A. Andronic et al., Nucl. Phys. A 772, 167 (2006). • Compressed Baryonic Matter @ FAIR – high mB, moderate T: • searching for the landmarks of the QCD phase diagram • first order deconfinement phase transition • chiral phase transition • QCD critical endpoint • in A+A collisions from 10-45 AGeV starting in 2015 • physics program complementary to ALICE • measurement of charm production at threshold

3. High density matter • high baryon and energy densities created in central Au+Au collisions • remarkable agreement between different models • max. net baryon densities from 5 - 40 AGeV ~ 1 - 2 fm-3 ~ (6 – 12) r0 • (net baryon density r = 1 fm-3 ~6r0) • max. excitation energy densities from 5 - 40 AGeV ~ (0.8 – 6) GeV/fm3 • (e* = e – mNr , e total energy density) [CBM physics group, J. Randrup priv. com.] net baryon density excitation energy density

4. Physics topics and Observables • The equation-of-state at high B • collective flow of hadrons • particle production at threshold energies (open charm) • Deconfinement phase transition at high B • excitation function and flow of strangeness (K, , , , ) • excitation function and flow of charm (J/ψ, ψ', D0, D, c) • sequential melting of J/ψ and ψ', charmonium suppression • QCD critical endpoint • excitation function of event-by-event fluctuations (K/π,...) • Onset of chiral symmetry restoration at high B • in-medium modifications of hadrons (,, e+e-(μ+μ-), D) • mostly new measurements • CBM Physics Book (theory) in preparation

5. The CBM experiment MVD + STS • tracking, momentum determination, vertex reconstruction: radiation hard silicon pixel/strip detectors (STS) in a magnetic dipole field • hadron ID: TOF (& RICH) • photons, p0, m: ECAL • PSD for event characterization • high speed DAQ and trigger → rare probes! • electron ID: RICH & TRD •  p suppression  104 • muon ID: absorber + detector layer sandwich •  move out absorbers for hadron runs aim: optimize setup to include both, electron and muon ID (not necessarily simultaneously)

6. CbmRoot simulation framework • detector simulation (GEANT3) • full event reconstruction: track reconstruction, add RICH, TRD and TOF info • result from feasibility studies in the following: central Au+Au collisions at 25 AGeV beam energy

7. STS tracking Challenge: high track density  600 charged particles in  25o • Task • track reconstruction: • 0.1 GeV/c < p  10-12 GeV/c • Dp/p ~ 1% (p=1 GeV/c) • primary and secondary vertex reconstruction (resolution  50 mm) • V0 track pattern recognition silicon pixel and strip detectors D+→ p+p+K- (ct = 317 mm) D0 → K-p+ (ct = 124 mm)

8. central Au+Au, 25 AGeV Open charm production • D0→ K-p+ (ct = 124 mm) • <D0> = 4∙ 10-5 • first MAPS detector at 10cm • ~53 mm secondary vertex resolution • proton identification with TOF 1.6 107 central Au+Au collisions, 25 AGeV

9. Silicon Strip Sensor R&D  4"280 µm Microstrip Sensors Tracking Stations layout studies module design J. Heuser HK 22.2

10. Fast self-triggered readout electronics micro-strip sensor NXYTER chip produced; DETNI − GSI test system under construction K. Solvag HK 34.8

11. central Au+Au, 25 AGeV Dileptons - electrons T. Galatyuk HK 19.3 • low-mass vector mesons: try to reject large physical background (g-conversion, Dalitz decays) by high performance tracking • J/y: cut on pt (1.2 GeV/c) • high purity of electron identification needed! (p-suppr. > 104 achievable) J/y meson low-mass vector mesons S/B=1.7 eff. 12% w S/B = 0.2 eff. 7.5% 100k events = 10s of beam time 1010 events

12. central Au+Au, 25 AGeV Dileptons - muons A. Kiseleva HK 19.4 • low efficiency for soft muons → investigate momentum dependent m identification • phantastic J/y (pt > 1 GeV/c), even y' should be accessible • however: high hit densities in detectors! low-mass vector mesons (1.25 m Fe) J/y meson (add 1m Fe) w S/B = 0.4 eff. 1.3% eff. 20% 4∙108 events

13. First test beam data → hit density? • hit densities after absorbers? • (reliability of simulation?) • first results from p test beam (6 GeV/c) at CERN, PS on high granularity gas detectors (ALICE prototypes): ADC counts → increase hit density in GEANT 3 appr. by factor 2 without Pb converter with Pb converter (1.5 cm ~ 3X0)

14. CBM collaboration China: CCNU Wuhan USTC Hefei Croatia: RBI, Zagreb Univ. Mannheim Univ. Münster FZ Rossendorf GSI Darmstadt Norway: Univ. Bergen Kurchatov Inst. Moscow LHE, JINR Dubna LPP, JINR Dubna Poland: Krakow Univ. Warsaw Univ. Silesia Univ. Katowice Nucl. Phys. Inst. Krakow LIT, JINR Dubna MEPHI Moscow Obninsk State Univ. PNPI Gatchina SINP, Moscow State Univ. St. Petersburg Polytec. U. Hungaria: KFKI Budapest Eötvös Univ. Budapest Cyprus: Nikosia Univ. India: VECC Kolkata SAHA Kolkata IOP Bhubaneswar Univ. Chandigarh Czech Republic: CAS, Rez Techn. Univ. Prague France: IPHC Strasbourg Portugal: LIP Coimbra Romania: NIPNE Bucharest Ukraine: Shevchenko Univ. , Kiev Univ. Varanasi IlT Kharagpur Korea: Korea Univ. Seoul Pusan National Univ. Russia: IHEP Protvino INR Troitzk ITEP Moscow KRI, St. Petersburg Germany: Univ. Heidelberg, Phys. Inst. Univ. HD, Kirchhoff Inst. Univ. Frankfurt Univ. Kaiserslautern 46 institutions > 400 members CBM related talks: M. Klein-Bösing HK 16.8 T. Galatyuk HK 19.3 A. Kiseleva HK 19.4 J. Heuser HK 22.2 K. Solvag HK 34.8 D. Gonzalez-Diaz HK 47.4 S. Gorbunov HK 53.1 C. Steinle HK 53.4 CBM related poster: C. Müntz HK 49.23 Strasbourg, September 2006