Grazyna Odyniec 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. RHIC) Experimental questions

Grazyna Odyniec IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, Exploring the rest of QCD phase diagram (T =0,  =0) by: - heavy ion collisions - lattice calculations (requires  /T not too large) “Locate” the CP (:= second order point where a line of 1 st 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 “QCD diagram is fairly EMPTY …” K.Rajagopal, INT, opening talk

Grazyna Odyniec IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, QCD phase diagram M.Stephanov, hep-ph/ v1 (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  B ~0 2. Various models find a strong 1st order transition at T~0 and large  B Either the theory is badly broken or there must be a critical point.

Grazyna Odyniec IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, Theory M.Stephanov, hep-ph/ v1 (March 2006) Predictions (models, lattice) for location of CP 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

Grazyna Odyniec IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, Lattice Reweighting : Fodor + Katz -> CP LR01, LR04 Imaginary  : D’Elia + Lombardo, de Forcrand+Philipsen -> no CP Taylor expansion of the pressure: Karsh, Gavai Gupta, -> CP LTE03, LTE04 ….  B CP T c (  =0) < or ~ 2 Several methods on lattice ( no agreement so far): Theory problem: including  B >0 “breaks” existing numerical techniques at a very basic level (the notorious “sign problem”)

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

Grazyna Odyniec IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, but No need to hit CP(!) – signature will be just as big if you pass anywhere in  B ~ 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  B !!! Experiment + Photons (PHENIX) Road Map by K.Rajagopal (INT,Aug.2008 ):

Grazyna Odyniec IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, “sQGP” at RHIC top energy LHC RHIC RHIC experiments in agreement (1)m T -N Q scaling (2)partonic collectivity (3)deconfinement At RHIC: hot and dense matter with partonic collectivity has been formed at RHIC

Grazyna Odyniec IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, Beam Energy Scan at RHIC:  s NN ~ 5-50 GeV experimental window to QCD phenomenology at finite temperature and baryon number density At RHIC : indications of sQGP found but remain unknown: (1) properties of hypothesized sQGP (2)boundary between hadronic and partonic phases (3)possible critical point

Grazyna Odyniec IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, Some indications of something new/not understood at lower energies – NA49 at SPS 40A GeV proton v 2 NA49 PRC collapse of proton v2 - signature of phase transition (Stoecker,Shuryak), but result depends on analysis technique … ? inconclusive non-monotonic K + /  + behavior,“horn”, but dynamical fluctuations quite monotonic…?

Grazyna Odyniec NA49 Results on the energy dependence of fluctuations: Onset of deconfinement Critical Point Charge Fluctuations: No sensitivity No predictions 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 ! INT, Seattle, August 2008 T.Schuster/M.Mitrovski for NA49/NA61: 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)

Grazyna Odyniec IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, BES at RHIC - access to large range of  B and T 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 - 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 … produces systems with lower freezout temperatures and higher baryon densities

Grazyna Odyniec IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, What should be measured during BES ? Mainly related to bulk properties yields and particle ratios T vs   particle spactra (p t, rapidity, …), strangeness production (K/ , multistrange, …), fluctuations and correlations of many varietes (K/ ,, HBT,v 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

Grazyna Odyniec IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, The Signature ! decrease sqrt (S) -> increase  B 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/  fluctuations have more chance than fluctuations -> lighter ions, shorter time in hadron gas phase – NA61 argument

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

Grazyna Odyniec IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, Triggering using BBCs impact parameter GeV BBC InnerBBC OuterBBC InnerBBC Outer 0<b< <b< <b< b> BBC is sensitive down to single MIP hitting the detector Studies indicate BBCs can be used for triggering during BES Multiplicity larger than that for p+p Triggering is not a problem

Grazyna Odyniec IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, Particle Identification in STAR TOF alone: ( ,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) log 10 (p) log 10 (dE/dx) TPC+TOF (completed in 2010)+EMC+Topology Good quality PID over a broad range: ~ 0.2 – 12 GeV/c

Grazyna Odyniec 18 STAR’s beam energy scan proposal (PAC 2008) √s NN (GeV) μ B (MeV) Rate (Hz) Events Duratio n (days) Test M M M M M M M6 14 weeks physics+1 week commissioning  B <500 ( Lattice)

Grazyna Odyniec IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 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, (2003) NA49 PRC66, (2002) NA49 EPJC33, S621 (2004) NA49 arXiv: v2 PHENIX PRC69, (2004) PHENIX PRL88, (2002) STAR PRL92, (2003) STAR PLB595, 143 (2004) Preliminary Sufficient data to extract ratios, flow velocity, HBT radii, v 2 Data fit into systematics D. Cebra QM2008

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

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

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

Grazyna Odyniec IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, Au+Au √s NN =9.2 GeV Uncorrected charged particle mid- rapidity p T spectra out to ~4GeV/c. (Not corrected. Can’t extract physics yet) STAR preliminary Clean PID for π, K, p + anti-particles All strange particles up to Λ _ Raw Yield 0.018/event Preliminary Invariant mass (pπ) [GeV/c 2 ] Preliminary

Grazyna Odyniec IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, The unique RHIC energy scan program will map the QCD diagram in  s NN =5-50 GeV, (corresponding to  B ~ MeV) –systematic study of collective dynamics and fluctuations with p, , , , , K, K*, ,  –turning off partonic activities (e.g. v 2 of ,  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 ? … ?

Grazyna Odyniec IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 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.

Grazyna Odyniec IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, THANKS !

Grazyna Odyniec IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, ETRA SLIDES

Grazyna Odyniec IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 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 Finding evidence for a 1 st order phase transition would immediately narrow location of the critical point. Correlation lengths expected to reach at most 2 fm (Berdnikov, Rajagopal and Asakawa, Nonaka) : reduces signal amplitude, no sharp discontinuities

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

Grazyna Odyniec IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, Luminosity is the key issue 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) Image courtesy of T.Satogata Total Event Rate [Hz] 33 Expect to reach γ 3 rate even at lowest energies Determined collision rate for GeV Au+Au test to be ~1Hz.

Grazyna Odyniec IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, RHIC run 10 (2010)  s NN [p ft ] GeV [GeV/c]  B [MeV] [Hz] Days/ Mevent # events# beam days 4.6 [9.6]570395M [18.8]470745M [27.9] M [37.7] M [71.0] M [161]220> M [391]150> M1.5 (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: CERN (starting in 2010): 10, 20, 30, 40, 80, 158 GeV/c