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Experimental Approach to the QCD Phase Diagram Beam Energy Scan at RHIC

Experimental Approach to the QCD Phase Diagram Beam Energy Scan at RHIC. Grazyna Odyniec/LBNL IV International Workshop on Correlations and Femtoscopy Krakow, September 10-14, 2008. Outline : QCD phase diagram - #1 single figure Lattice and HI exp. (BES @ RHIC)

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Experimental Approach to the QCD Phase Diagram Beam Energy Scan at RHIC

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  1. Experimental Approach to the QCD Phase DiagramBeam Energy Scan at RHIC Grazyna Odyniec/LBNL IV International Workshop on Correlations and Femtoscopy Krakow, September 10-14, 2008 Outline : QCD phase diagram - #1 single figure Lattice and HI exp. (BES @ RHIC) Experimental questions

  2. “QCD diagram is fairly EMPTY …” K.Rajagopal, INT, opening talk Exploring the rest of QCD phase diagram (T =0, m=0) by: - heavy ion collisions - lattice calculations (requires m/T not too large) “Locate” the CP (:= second order point where a line of 1st order transition ends) either - via experimental detection of signatures - via lattice calculations Stress on plural ! - need agreement of several signatures - need agreement of different calculations IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

  3. QCD phase diagram M.Stephanov, hep-ph/0402115v1 (March 2006) • Theory at the “edges” is believed to be well understood: 1. Lattice QCD finds a rapid, but smooth, crossover at large T and mB~0 2. Various models find a strong 1st order transition at T~0 and large mB Either the theory is badly broken or there must be a critical point. IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

  4. Theory Predictions (models, lattice) for location of CP M.Stephanov, hep-ph/0402115v1 (March 2006) be careful ! this figure is of great historical interest but it does not represent the span of theories that are currently given strong credibility Lattice IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

  5. Lattice Several methods on lattice (no agreement so far): • Reweighting : Fodor + Katz -> CP LR01, LR04 • Imaginary m: D’Elia + Lombardo, de Forcrand+Philipsen -> no CP • Taylor expansion of the pressure: Karsh, Gavai Gupta, -> CP LTE03, LTE04 • …. mBCP Tc(m=0) < or ~ 2 Theory problem: including mB>0 “breaks” existing numerical techniques at a very basic level (the notorious “sign problem”) IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

  6. hep-lat/0701002v1 Lattice - green points ! mB<500 Given the very significant theoretical difficulties, data may lead the study of QCD phase diagram … IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

  7. Road Map by K.Rajagopal (INT,Aug.2008 ): Experiment + Photons (PHENIX) but No need to hit CP(!) – signature will be just as big if you pass anywhere in mB ~ 100 MeV (Hatta+Ikeda model, estimate is both crude and uncertain, it would be good to get it on lattice) Focusing of trajectories that pass near the critical point = NO need to take very small steps in mB !!! IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

  8. “sQGP” at RHIC top energy RHIC At RHIC: LHC • mT-NQ scaling • partonic collectivity • deconfinement RHIC experiments in agreement hot and dense matter with partonic collectivity has been formed at RHIC IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

  9. Beam Energy Scan at RHIC: sNN ~ 5-50 GeVexperimental window to QCD phenomenologyat finite temperature and baryon number density • At RHIC : indications of sQGP found • but remain unknown: • properties of hypothesized sQGP • boundary between hadronic and partonic phases • possible critical point IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

  10. Some indications of something new/not understood at lower energies – NA49 at SPS NA49 PRC 40A GeV proton v2 non-monotonic K+/p+ behavior,“horn”, but dynamical fluctuations quite monotonic…? collapse of proton v2 - signature of phase transition (Stoecker,Shuryak), but result depends on analysis technique … ? inconclusive IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

  11. INT, Seattle, August 2008 T.Schuster/M.Mitrovski for NA49/NA61: NA49 Results on the energy dependence of fluctuations: Onset of deconfinement Critical Point Charge Fluctuations: No sensitivity No predictions <pT> Fluctuations: No predictions No signal observed Multiplicity Fluctuations: No sensitivity No signal observed Hadron Ratio Fluctuations: No quantitative predictions • but the structure seen in the energy dependence of K/π fluctuations cannot be explained in a hadronic scenario ! Very nice analysis of Pb+Pb at sqrt(S)= 6.3, 7.6, 8.8, 13.3, 17.3 GeV no dependence on sqrt(S)

  12. BES at RHIC - access to large range of mB and T produces systems with lower freezout temperatures and higher baryon densities • -explore a broad region of the QCD phase diagram • -look for the evidence of ordered transition • -study the evolution with beam energy of the unusual medium properties found at RHIC • do any of the partonic properties change or “turn off” ? • new surprises in unexplored region … advantage of collider geometry ! At fixed target geometry: detector acceptance changes with energy track density at mid-y increases fast with energy -> technical difficulties in tracking IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

  13. What should be measured during BES ? Mainly related to bulk properties yields and particle ratios T vs mB, particle spactra (pt, rapidity, …), strangeness production (K/p, multistrange, …), fluctuations and correlations of many varietes (K/p,<pt>, HBT,v2@CP,…) flow (v1,v2,v4, …) with charged and identified particles, signals of parity violation, “lumpy”(“clumpy” ?) final state prospect of data will “encourage” theorists to be more specific Search for : - disappearance of partonic activities - fluctuations, correlations turn on and off signature of deconfinement IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

  14. The Signature ! decrease sqrt (S) -> increase mB The signature is a CHANGE (not observable itself) = rise and then fall of Gaussian e-by-e fluctuations of: …. …. Note, number fluctuations will better survive the late time hadron gas so, K/p fluctuations have more chance than <pt> fluctuations -> lighter ions, shorter time in hadron gas phase – NA61 argument IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

  15. Excellent match with STAR detector capabilities and existing, well understood STAR analysis techniques. STAR after 2010 : FTPC Compatibility of FTPCs and FGT/HFT under investigation (only issue if run after 2010) Other anticipated/studied issues: triggering and PID IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

  16. Triggering using BBCs Studies indicate BBCs can be used for triggering during BES Multiplicity larger than that for p+p BBC is sensitive down to single MIP hitting the detector Triggering is not a problem IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

  17. Particle Identification in STAR log10(dE/dx) log10(p) TPC+TOF (completed in 2010)+EMC+Topology • TOF alone: (p,K) up to 1.6 GeV/c, p up to 3 GeV/c • TOF+TPC(dE/dx, topology) up to 12 GeV (NIMA 558 (419) 2006) Good quality PID over a broad range: ~ 0.2 – 12 GeV/c IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

  18. STAR’s beam energy scan proposal (PAC 2008) 14 weeks physics+1 week commissioning mB<500 (Lattice)

  19. STAR experience with Low Energy RHIC running 2001: 19.6 GeV Au+Au 2004: 22.4 GeV Cu+Cu 2007: 9 GeV Au+Au 2008: 9 (5) GeV Au+Au ! E802 PRL81, 2650 (1998) E866 PLB476, 1 (2000) E917 PLB490, 53 (2000) NA44 PLB471, 6 (1999) WA98 PRC67, 104906 (2003) NA49 PRC66, 054902 (2002) NA49 EPJC33, S621 (2004) NA49 arXiv:0710.0118v2 PHENIX PRC69, 034909 (2004) PHENIX PRL88, 242301 (2002) STAR PRL92, 112301 (2003) STAR PLB595, 143 (2004) Preliminary D. Cebra QM2008 Preliminary Sufficient data to extract ratios, flow velocity, HBT radii, v2 Data fit into systematics IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

  20. 2008: low energy run with 9.2 GeV Au+Au Injecting and colliding Au+Au√sNN = 9.2 GeV, a few hours -> 4K good events ! Short test @√sNN = 5 GeV allowed study of beam optics IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

  21. some preliminary plots from 9.2 GeV analysis STAR preliminary shown by H.Caines at INT, August 2008 primary vertex Raw multiplicity IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

  22. Au+Au and Au+Al collisions ! Au+Al Au+Al Au+Be Vertex Z (cm) Investigated primary vertex location: They are “real”collisions. Au+Au collisions Au+Beampipe collisions Vertex Y R. Reed Vertex X Can see the change in beampipe material and thickness IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

  23. Au+Au √sNN=9.2 GeV Preliminary Preliminary STAR preliminary _ All strange particles up to Λ Raw Yield 0.018/event Clean PID for π, K, p + anti-particles Invariant mass (pπ) [GeV/c2] Uncorrectedcharged particle mid-rapidity pTspectra out to ~4GeV/c. (Not corrected. Can’t extract physics yet) IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

  24. The unique RHIC energy scan program will map the QCD diagram in sNN =5-50 GeV, (corresponding to mB ~ 600-150 MeV) • systematic study of collective dynamics and fluctuations with p, L, X, W, p, K, K*, r, f... • turning off partonic activities (e.g. v2 of f, W, D – no NQ scaling, quenching ->0, …) but … • experimentalist’s questions: Can we get as quantitative as possible about critical line shape and use hydro or something else to connect freeze-out point to it ? Can we try to predict freezout versus sqrt(s) with and without CP ? … ? IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

  25. Experimentalist’s request to the community of correlations/fluctuations experts : other signals of the first order phase transition and CP new analysis techniques, tools (correlations, fluctuations, ?) We will study all of them with the data. First run soon. IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

  26. THANKS ! IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

  27. ETRA SLIDES IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

  28. If there, a critical point doesn’t hide… Image courtesy of C.Nonaka • Hydro predicts that the evolution of the system is attracted to the critical point. • Effect observed already for liquid-gas nuclear transition • Focusing causes broadening of signal region - No need to run at exactly Critical Point energy Correlation lengths expected to reach at most 2 fm (Berdnikov, Rajagopal and Asakawa, Nonaka):reduces signal amplitude, no sharp discontinuities Finding evidence for a 1st order phase transition would immediately narrow location of the critical point. IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

  29. Colliders are a great choice for E-scan Acceptance π NA49 K • Occupancy for collider detectors is much less dependent on beam energy • Less problems with track merging, charge sharing hits etc.. π K STAR Acceptance for collider detectors is totally independent of beam energy Better control of systematics IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

  30. Luminosity is the key issue γ3 Image courtesy of T.Satogata Total Event Rate [Hz] Determined collision rate for 2008 9 GeV Au+Au test to be ~1Hz. • Rate can be increased by: • factor 2 by adding more bunches - only 56 used for tests (max 120). • factor 3-6 by operating with higher charge in bunches. • factor few by running in continuous injection mode • electron cooling in RHIC (?) (not helpful at lower √s) Expect to reach γ3 rate even at lowest energies IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

  31. RHIC run 10 (2010) (1) Large energy range accessible (2) Collider geometry (acceptance won’t change with S, track density varies slowly) (3) RHIC detectors well suited (large acceptance), tested & understood STAR PAC 2007 Strawman proposal: Note: NA61 @ CERN (starting in 2010): 10, 20, 30, 40, 80, 158 GeV/c IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008

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