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The Search for the Critical Point of QCD: STAR Capabilities for Low s NN Running

The Search for the Critical Point of QCD: STAR Capabilities for Low s NN Running. OUTLINE Motivation Theoretical predictions Results from SPS and RHIC Low sqrt(s) RHIC running RHIC conditions RHIC limitations STAR Capabilities Trigger Physics Event Rates & requirements

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The Search for the Critical Point of QCD: STAR Capabilities for Low s NN Running

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  1. The Search for the Critical Point of QCD: STAR Capabilities for Low sNNRunning • OUTLINE • Motivation • Theoretical predictions • Results from SPS and RHIC • Low sqrt(s) RHIC running • RHIC conditions • RHIC limitations • STAR Capabilities • Trigger • Physics • Event Rates & requirements • Summary Tapan Nayak (for the STAR Collaboration) Workshop: Can We Discover QCD Critical Point at RHIC Brookhaven National Laboratory March 9-10, 2006 Workshop: Can We Discover the QCD Critical Point at RHIC

  2. The phase diagram Lattice Neutron STAR • SPS top energy is below the curve and RHIC data so far are above. • It will be worth having a look at the systems produced near the QCD phase boundary. • RHIC has a unique possibility to scan the full range from AGS to top RHIC energy. Workshop: Can We Discover the QCD Critical Point at RHIC

  3. Lattice predictions Gavai, Gupta hep-lat/0412035 F. Karsch, Prog. Theor. Phys. Suppl. 153, 106 (2004) CRITICAL END POINT Energy Density Temperature Lattice calculations suggest that the Critical Point of QGP phase transition may be located at about the SPS energies (c.m. energy of 5-20 GeV/nucleon) TC ~ 170 15 MeV eC ~ 0.7-1.5 GeV/fm3 Workshop: Can We Discover the QCD Critical Point at RHIC

  4. Bjorken estimation of initial energy density pR2 AuAu 10GeV (estimated) 10GeV Boost invariant hydrodynamics: Bjorken density as function beam energy Bjorken density as function of #of participants STAR Preliminary RaghunathSahoo, STAR Assuming Bjorken energy density is similar to that of the lattice calculation: in order to probe the Critical Point (eC ~ 0.7-1.5 GeV/fm3) – the c.m. beam energy need to be between 5-20GeV. Workshop: Can We Discover the QCD Critical Point at RHIC

  5. <r> [c] Tth [GeV] STAR 4.6 Kinetic freezeout from AGS->RHIC <ßr> (RHIC) = 0.55 ± 0.1 c TKFO(RHIC) = 100 ± 10 MeV • Rapid change in freeze-out temperature and flow velocity between 2-20GeV • Explosive Transverse Expansion • at RHIC  High Pressure Workshop: Can We Discover the QCD Critical Point at RHIC

  6. Elliptic flow: The scaling of v2/ε The scaling of the strength of the elliptic flow v2 with eccentricity shows that a high degree of collectivity is built up at a very early stage of the collision. With low energy beam the lower points can be scanned more precisely. Workshop: Can We Discover the QCD Critical Point at RHIC

  7. Energy dependence of <mT> and temperature 4.6 Inverse slope parameter (MeV) • Rapid rise in <mT> going from AGS to SPS energies and slowing down towards RHIC. • Step like behavior in the inverse slope parameter in heavy-ions around SPS energies, but not in pp. Mohanty, Alam, Sarkar, Nayak, Nandi PRC 68 (2003) 021901 Workshop: Can We Discover the QCD Critical Point at RHIC

  8. 4.6 Energy dependence of particle ratio and fluctuations Particle Ratio: K/p shows increasing behavior with energy, whereas a horn structure seen in K+/p+ <K/p> <K+/p+> • Fluctuation in Ratio: • K/p fluctuations increase towards lower beam energy. • p/p fluctuations are negative, indicating a strong contribution from resonance decays • STAR results are being finalized. Christof Roland (NA49) Workshop: Can We Discover the QCD Critical Point at RHIC

  9. Beam energy dependence of pion HBT 4.6 STAR S. Voloshin, QM02 Debasish Das Pion rapidity density is proportional to the freezeout volume => Constant Freezeout Volume (freezeout at a constant density). Workshop: Can We Discover the QCD Critical Point at RHIC

  10. STAR Preliminary Pb+Pb Au+Au STAR Preliminary Energy dependence of strange baryon production Sevil Salur, QM2005 s-Baryon production rises smoothly at mid-rapidity. Constant s-Baryon production at mid-rapidity. Workshop: Can We Discover the QCD Critical Point at RHIC

  11. STAR Preliminary Energy dependence of ratio of strange baryons Sevil Salur, QM2005 • The ratio of strange to anti-strange baryons goes up with energy. • At RHIC energies the production of strange and anti-strange baryons is equal. Anti-baryon/baryon ratio Workshop: Can We Discover the QCD Critical Point at RHIC

  12. Gary Westfall, STAR Panos Christacoglou, NA49 preliminary W Energy dependence of balance functions W is a normalized measure of the time of hadronization with respect to uncorrelated data sample. This is consistent with delayed hadronization at RHIC compared to SPS energies. Workshop: Can We Discover the QCD Critical Point at RHIC

  13. <pT> fluctuations Fractional increase of width of the <pT> distribution w.r.t. to a statistical reference. Establishing the scale for studying <pT> fluctuations. Workshop: Can We Discover the QCD Critical Point at RHIC

  14. 200 GeV correlations fluctuations Understanding contribution of minijets at low pT • STAR has the capability to study fluctuations in fine bins of h and f. • The localized measures of fluctuation is necessary to understand the underlying structure in an event including the contribution of mini-jets. • Study of the phase boundary at large sNNhas to take the presence of minijets into account. • Minijets might help in our understanding of the phase boundary. Workshop: Can We Discover the QCD Critical Point at RHIC

  15. A note on low energy RHIC running From: Wolfram Fischer, BNL C-AD Nov 2005 • No hard limit for the RHIC collision energy down to c.m. energy of 4.6 GeV/n. • The beam and luminosity lifetimes will decrease gradually with the lower energies. • Because the ZDC counters will be ineffective – tuning can be done using Beam-Beam-Counters (BBC). • Low Energy beam runs including cooling has to be tested in advance. • Details: • Current regulation of the main dipoles should work even at 50A. • During RUN-2 with AuAu collisions of 9.8GeV/n beams, luminosity was delivered at a rate of 1 inv. micro-barn/week. The rates drop with about gamma^3 to gamma^4 • Operation near AGS transition energy has to be checked. • Electron cooling at low energies needs study. Workshop: Can We Discover the QCD Critical Point at RHIC

  16. The STAR experiment Large acceptance: 2p coverage at mid-rapidity Magnet Coils Central Trigger Barrel (CTB) ZCal Time Projection Chamber (TPC) Year 2000 Barrel EM Cal (BEMC) Silicon Vertex Tracker (SVT)Silicon Strip Detector (SSD) FTPCEndcap EM CalFPD TOFp, TOFr FPD Year 2001+ PMD Workshop: Can We Discover the QCD Critical Point at RHIC

  17. Hadron identification: STAR Collaboration, nucl-ex/0309012 Inclusion of ToF detector ToF Fabrication of MRPC based Time-of-Flight (ToF) detector for STAR is in progress. It is scheduled to be installed for RHIC RUN-9. The STAR experiment (with the inclusion of TOF) is an ideal detection device to search for the Critical Point of QCD and to carry on a systematic study of majority of the physics topics being addressed. Workshop: Can We Discover the QCD Critical Point at RHIC

  18. Particle production at low sNNenergies uRQMD Pseudo-rapidity distribution of charged particles at 4 different centralities. Workshop: Can We Discover the QCD Critical Point at RHIC

  19. Second order event-plane resolution STAR TPC Acceptance sNN = 8.75GeV Event plane resolution in STAR will be better than what was achieved at NA49. Coverage in terms of beam-rapidity increases as we go to lower energies. Workshop: Can We Discover the QCD Critical Point at RHIC

  20. STAR Trigger for Low Energy RHIC Running Trigger Detectors in STAR CTB FPD FPD ZDC ZDC BBC BBC BEMC & EEMC (only a part of the detectors shown) We set up all collision triggers (e.g. ZDC coin., BBC coin., CTB multiplicity, etc) and run them all simultaneously without pre-scales. Workshop: Can We Discover the QCD Critical Point at RHIC

  21. Triggering with STAR Beam-Beam Counter (BBC) STAR uses two BBCs wrapped around the beampipe: one on either side of the TPC. Each counter consists of two rings of hexagonal scintillator tiles: an outer ring composed of large tiles and an inner ring composed of small tiles. Internally, each ring is divided into two separate sub-rings of 6 and 12 tiles each. Table below gives the #of particles within BBC coverage for two c.m. energies and four different centralities: BBC is sensitive down to single MIP falling on the detector. BBC can effectively be used for triggering for low energy runs. Workshop: Can We Discover the QCD Critical Point at RHIC

  22. STAR physics: option-1 (for low energy RHIC running) • Particle spectra (pT, (pseudo)-rapidity distributions) • Flow (v1, v2, v4 ….) with charged and identified hadrons • Strangeness production (k/pi ratio) • Resonance • HBT Radii • Fluctuations (net charge, k/pi ratio, baryon number….) • Correlations • Formation of Disoriented Chiral Condensates (DCC) • Using PMD–FTPC and BEMC–TPC • Long range (forward-backward) correlations Workshop: Can We Discover the QCD Critical Point at RHIC

  23. Required statistics for different observables At sNN = 10GeV Very basic measurement: 2M events Limit for a thorough measurement: 20M events Workshop: Can We Discover the QCD Critical Point at RHIC

  24. BBC Coincidence Rate for CuCu 20GeV BBC ZDC BBC Coincidence Rates and Beam-time estimation for option-1 CuCu 20GeV: beginning of spill: 3000 average over time: ~1000 AuAu 20GeV: 1000/4 = 250. Optimistic view: rates scale as g3 This energy scan will take a total of 17 weeks for STAR physics Option-1. Workshop: Can We Discover the QCD Critical Point at RHIC

  25. STAR physics: Option-2 (for low energy RHIC running) • All STAR Physics Option-1 and in addition: • v2 of Omega (centrality dependence) • v2 of phi (centrality dependence) • Jet quenching, Energy loss (RAA and RCP). • For RAA: pp reference will be needed. > 50M events needed at each energy. A high statistics energy scan will take total of 25 weeks. This option is preferable. Workshop: Can We Discover the QCD Critical Point at RHIC

  26. Beam-time estimation for a basic energy scan March 10, 2006 • cleanup • vertex • efficiency • Gunter: 200K 0-5%, minbias:4M 5M events: 12.5 weeks: JUST enough, Errors factor 2-4 better than NA49 Workshop: Can We Discover QCD Critical Point at RHIC Brookhaven National Laboratory March 9-10, 2006 Workshop: Can We Discover the QCD Critical Point at RHIC

  27. RHIC QCD Critical Point Discoveries Ahead Summary • The QCD phase boundary is worthy of study, including that of the tri-critical point. • STAR experiment with the inclusion of TOF will be the ideal place for this study. • Current investigations don’t indicate any problem carrying out this program with the STAR detector. • The RHIC program looks most promising. AGS SPS RHIC Physics measure Energy Density Workshop: Can We Discover the QCD Critical Point at RHIC

  28. Discoveries Ahead • Thanks to STAR Collaborators and in particular: • Paul Sorensen • Bill Christie • Jamie Dunlop • Nu Xu • Zhangbu Xu • Peter Seyboth • Tim Hallman Thanks to the organizers of the Workshop: “Can We Discover QCD Critical Point at RHIC” Brookhaven National Laboratory March 9-10, 2006 Workshop: Can We Discover the QCD Critical Point at RHIC

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