The CBM experiment

1. rare probes! target magnet • Challenge for vector mesons decaying into dileptons: • r, w, f : e+e-→ reject e± from g-conversion and Dalitz decays • m+m-→ measure low-momentum m (p-dependent m-id. ?) • J/y : → study feasibility of y' measurement in muon channel phase space distribution of identified hadrons 105 central Au+Au collisions, 25 AGeV 109 central Au+Au collisions, 25 AGeV p p J/y K Challenge for open charm measurement: identify by secondary vertex reconstruction D+→ p+p+K- (ct = 317 mm) D0 → K-p+ (ct = 124 mm) w e+e- pairs f reconstructed strange baryons 1012 minimum bias Au+Au collisions, 25 AGeV Multiplicities in central Au+Au collisions, 25 AGeV (HSD): r = 23 w = 38 f= 1.24 J/y = 1.9∙10-5y' = 2.6∙10-7 D0+ D0=1.5∙10-4 (1/5 for min. bias) 106 central Au+Au collisions, 25 AGeV 107 central Au+Au collisions, 25 AGeV L X W J/ w D0 ' ? f m+m- pairs r China: CCNU Wuhan USTC Hefei Croatia: RBI, Zagreb Cyprus: Nikosia Univ. Univ. Mannheim Univ. Münster FZ Rossendorf GSI Darmstadt Univ. Varanasi IlT Kharagpur Korea: Korea Univ. Seoul Pusan National Univ. Norway: Univ. Bergen Portugal: LIP Coimbra Romania: NIPNE Bucharest LIT, JINR Dubna MEPHI Moscow Obninsk State Univ. PNPI Gatchina SINP, Moscow State Univ. St. Petersburg Polytec. U. Czech Republic: CAS, Rez Techn. Univ. Prague France: IPHC Strasbourg Hungaria: KFKI Budapest Eötvös Univ. Budapest Russia: IHEP Protvino INR Troitzk ITEP Moscow KRI, St. Petersburg Kurchatov Inst. Moscow LHE, JINR Dubna LPP, JINR Dubna Ukraine: Shevchenko Univ. , Kiev India: VECC Kolkata SAHA Kolkata IOP Bhubaneswar Univ. Chandigarh Poland: Krakow Univ. Warsaw Univ. Silesia Univ. Katowice Nucl. Phys. Inst. Krakow Germany: Univ. Heidelberg, Phys. Inst. Univ. HD, Kirchhoff Inst. Univ. Frankfurt Univ. Kaiserslautern The CBM experiment at FAIR – exploring the QCD phase diagram at high net-baryon densities – Claudia Höhne for the CBM collaboration – GSI Darmstadt, Germany CBM = Compressed Baryonic Matter FAIR = Facility for Antiproton and Ion Research The physics case • Mapping the QCD phase diagram • What do we know from theory? → Predictions from lattice QCD: • crossover transition from partonic to hadronic matter at small mB and high T, Tc(mB=0) = 151 – 192 MeV [1-3] • critical endpoint in intermediate range of the phase diagram (current estimates mB = 300 – 700 MeV, T ≈ 140 – 160 MeV) [1-3] • first order deconfinement phase transition at high mB but moderate T • What do we know from experiment? → Heavy-ion collisions: • chemical freeze-out curve from final hadron yields measured in the experiments: T ≈ 160 MeV at top RHIC energy [5] • top SPS, RHIC (high T, low mB): indications for relevance of partonic degrees of freedom • lower SPS, AGS (intermediate T-mB range): intriguing observations around 30 AGeV beam energy • Observables • Goal of CBM experiment: comprehensive and systematic (energy, system size) studies of all relevant diagnostic probes including: • hadrons, event-by-event fluctuations, correlations, collective flow • multistrange hyperons • low-mass vector mesons • open charm (D0, D±, Lc) • charmonium (J/y, y') • → CBM@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 [W. Cassing, E. Bratkovskaya, A. Sibirtsev, Nucl. Phys. A 691 (2001) 753] CBM energies: enormous energy and baryon densities reached! e >> 1GeV/fm3r ~ 8-10 r0 [Andronic et al. [5]] [E. Bratkovskaya, C. Fuchs priv. com.] CBM energy range [1] Y. Aoki, Z. Fodor, S.D. Katz and K.K. Szabo, hep-lat/0609068. [2] M. Cheng et al., Phys. Rev. D, 054507 (2006). [3] C. Schmidt et al., PoS LAT2005, 163 (2006). Z. Fodor, S.D. Katz, JHEP 0404, 050 (2004). [4] S. Ejiri et al., Prog. Theor. Phys. Suppl. 153, 118 (2004). C.R. Allton et al., Phys. Rev. D 68, 0145507 (2003). [5] A. Andronic et al., Nucl. Phys. A 772, 167 (2006). The CBM experiment • CBM will be a fixed target detector measuring hadrons and leptons in p+p, p+A, and A+A collisions in the beam energy range between 10-45 AGeV (ion beams) and up to 90 GeV for protons, up to 10MHz interaction rate for rare probes: • track reconstruction for tracks with 0.1 GeV/c < p ≤ 10-12 GeV/c and with a momentum resolution of ~1% at 1 GeV/c • primary and secondary vertex reconstruction (resolution ≤ 50mm) • radiation hard silicon pixel/strip detectors (STS) in a magnetic dipole field • high purity of particle identification • electron ID: RICH & TRD (& ECAL) •  p suppression  104 • hadron ID: TOF (& RICH) • photons, p0, m: ECAL • PSD for event characterization • high speed DAQ and trigger Alternative setup studied for exploring the muon-decay channel of vector mesons: sequence of absorber layers (Fe+C) and tracking detectors after the STS ... move out absorbers for hadron runs. region of STS in a central Au+Au collision at 25 AGeV: ~600 charged particles in ± 25° absorber – detector layers Feasibility studies The CBM collaboration: 46 institutions, > 400 members CBM collaboration meeting, Strassbourg, France, September 2006 Contact Claudia Höhne Peter Senger (spokesperson) c.hoehne@gsi.dep.senger@gsi.de