The C ompressed B aryonic M atter experiment

1. The Compressed Baryonic Matter experiment Claudia Höhne, GSI Darmstadt CBM collaboration • Outline • physics case, observables • detector layout • feasibility studies • (R&D of detector components)

2. CBM @ FAIR

3. Physics case Q: Why do we want to build yet another heavy-ion experiment? • What do we know from theory? → Predictions from lattice QCD: • crossover transition from partonic to hadronic matter at small mB and high T • critical endpoint in intermediate range of the phase diagram • first order deconfinement phase transition at high mB but moderate T

4. Physics case (II) • What do we know from experiment? → Heavy-ion collisions: • chemical freeze-out curve • top SPS, RHIC (high T, low mB): • partonic degrees of freedom ? • lower SPS, AGS (intermediate T-mB): • intriguing observations around 30 AGeV! [Andronic et al. Nucl. Phys. A 772, 167 (2006).

5. Physics case (III) Q: Why do we want to build yet another heavy-ion experiment? • 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 (√sNN = 4.5 – 9.3 GeV) starting in 2015

6. Dense baryonic matter Q: Do we reach energy densities high and long enough in order to reach a deconfined phase? • baryon density in central cell (Au+Au, b=0 fm) in transport calculations HSD (mean field, hadrons + resonances + strings) • enormous energy and baryon densities reached! (e > ecrit ~ 1GeV/fm3) [CBM physics group, C. Fuchs, E. Bratkovskaya priv. com.]

7. High baryon density matter! Q: Why do we want to measure particles also at high baryon densities? • hadronic properties should be effected by the enormous baryon densities • relation to (partial) restoration of chiral symmetry? • equation of state? [Rapp, Wambach, Adv. Nucl. Phys. 25 (2000) 1, hep-ph/9909229] [Mishra et al ., PRC 69, 015202 (2004) ] D r

8. Physics topics and Observables Q: How to measure? What to look for? • The equation-of-state at high B • collective flow of hadrons • particle production at threshold energies (open charm) side remark: equation of state at high baryon densities → relation to inner core of neutron stars! Grigorian, Blaschke, Klähn astro-ph/0612783

9. D-mesons in matter [W. Cassing, E. Bratkovskaya, A. Sibirtsev, Nucl. Phys. A 691 (2001) 745] D-mesons sensitive to medium (EOS)! SIS100/ 300 SIS18 [Mishra et al ., PRC 69, 015202 (2004)]

10. D-mesons in matter (II) • charm production studies at threshold: steeply rising cross section • dropping D-meson mass might give a large enhancement • measure energy dependence! • impact on flow! [E. Bratkovskaya, W. Cassing, private communication] charm quark as probe for dense matter created at FAIR

11. Physics topics and Observables Q: How to measure? What to look for? • 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

12. Excitation function • For (K, , , , ,..........) measure with high precision • particle production • kinetic distributions • flow • correlations • ....... • in dependence on energy, system-size (centrality),... • → observe changes? • in ideal case for several observables at the same energy transition hadron gas QGP [NA49]

13. Collective flow central midcentral peripheral v2 • collapse of elliptic flow of protons at lower energies signal for first order phase transition?![e.g. Stoecker, NPA 750 (2005) 121, E. Shuryak, hep-ph/0504048] • full energy dependence needed! elliptic flow v2: initial overlap eccentricity → particle azimuthal distributions f [NA49, PRC68, 034903 (2003)]

14. Collective flow (II) • RHIC • all particles flow: strong collective behaviour! • impressive scaling of flow observed • relation to quark content of hadrons! • → partonic degrees of freedom relevant in early phase! • when does it break down? KET=mT-m

15. Collective flow (III) charm quark as probe for dense matter created at FAIR • does charm flow at all energies? • break down of charm flow?

16. Charmonium suppression Quarkonium dissociation temperatures – Digal, Karsch, Satz • cc production • at threshold for CBM energies! • cc produced in first inelastic interactions • pp: certain probability to form a J/y (or y') • AA: dissolved in medium? • ... difference for J/y and y'? • (sequential melting?) measure energy and system-size dependence!

17. Physics topics and Observables Q: How to measure? What to look for? • 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,...)

18. Fluctuations [C.Roland et al., nucl-ex/0403035 S. Das, SQM06] K/p • difficulty: subtract all "trivial" fluctuations (statistical, acceptance, other correlations,...) • dynamical fluctuations of the K/p ratio increase towards lower energies  energy dependence needed for lower energies (and a better understanding)!

19. Physics topics and Observables Q: How to measure? What to look for? • 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)

20. Dileptons  n  p p  ++ K e+, μ+ r e-, μ- Dileptons are penetrating probes! lifetime of r-meson 1.3 fm/c → probe the early fireball! (ct of : w – 23 fm/c, f – 44 fm/c, J/y – 2.3 fm/c)

21. Dileptons (II) hep-ph/0604269 • new results from top SPS energy (√sNN = 17.3 GeV): • → modification of r spectral function, importance of baryons! • measure in dependence on baryon density (energy)! CERES NA60

22. Dileptons (III) Q: What is the best way to measure? e+e-↔ m+m-

23. Physics topics and Observables Q: How to measure? What to look for? • 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) CBM Physics Book (theory) in preparation

24. The CBM experiment • tracking, momentum determination, vertex reconstruction: radiation hard silicon pixel/strip detectors (STS) in a magnetic dipole field • electron ID: RICH & TRD •  p suppression  104 • hadron ID: TOF (& RICH) • photons, p0, m: ECAL • PSD for event characterization • high speed DAQ and trigger high interaction rate long beamtime → rare probes! STS

25. Modified CBM setup → dimuons • for investigation of dimuons study alternative CBM setup with active muon absorbers (Fe + C + detector layers) after the STS • ... move absorbers out for hadron runs

26. Dileptons - electrons central Au+Au, 25 AGeV • low-mass vector mesons: try to reject large physical background (g-conversion, Dalitz decays) by high performance tracking • J/y: cut on pt (1.2GeV) • high purity of electron identification needed! J/y meson low-mass vector mesons S/B=1.7 eff. 12% w S/B = 0.2 eff. 7.5%

27. Dileptons - muons central Au+Au, 25 AGeV • low efficiency for soft muons → use momentum dependent m identification? • phantastic J/y, even y' should be accessible • however:high hit densities in detectors! low-mass vector mesons J/y meson w S/B = 0.42 eff. 1.8% S/B ~ 30 eff. 13%

28. 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 D+→ p+p+K- (ct = 317 mm) D0 → K-p+ (ct = 124 mm)

29. Open charm production central Au+Au, 25 AGeV • D0→ K-p+ (ct = 124 mm) • <D0> = 4∙ 10-5 → ~ 2 D0/s for 1MHz interaction rate (minbias Au+Au) • first MAPS detector at 10cm • ~53 mm secondary vertex resolution • proton identification via TOF • even better signal for • D+ → K-p+p+ • (3-particle 2nd vertex) 1.6 107 central Au+Au collisions, 25 AGeV

30. 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 Strasbourg, September 2006

31. Physics case Q: Why do we want to build yet another heavy-ion experiment? • 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 (√sNN = 4.5 – 9.3 GeV) starting in 2015

32. additional slides

33. 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

34. STS tracking (II) • set of silicon tracking stations inside magnetic field („heart of CBM“) • MVD for high precision vertex resolution • Si strip for main tracker • challenge: readout speed (10 MHz interaction rate), radiation hardness (109 ions/s), material budget, resolution • layout simulations • Si-strip sensor design • system integration • fast self-triggered readout

35. STS R&D  4"280 µm Microstrip Sensors Tracking Stations layout studies module design

36. fast self-triggered readout electronics micro-strip sensor NXYTER chip produced; DETNI − GSI test system under construction

37. Hadron identification – TOF (RPC) simulations: time resolution 80ps, TOF wall in 10m distance to target

38. D-mesons in matter [W. Cassing, E. Bratkovskaya, A. Sibirtsev, Nucl. Phys. A 691 (2001) 745] SIS18 [M. Lutz, Phys. Lett. B 426, 12 (1998)] us repulsive potential us attractive potential

39. Sequential dissociation of charmonium? (J/)/DY = 29.2  2.3 L = 3.4 fm Preliminary! Quarkonium dissociation temperatures – Digal, Karsch, Satz Preliminary! [NA60]

40. Fluctuations (II) • However .... • mean-pt (SpT) fluctuations rather constant • changing fluctuations of net electric charge ndyn? •  importance of resonance decays?! [H. Appelshaeuser and H. Sako for CERES, nucl-ex/0409022] [CERES, NPA 727, 97 (2003)]