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STAR Results from RHIC Beam Energy Scan-I

Lokesh Kumar (for STAR Collaboration). STAR Results from RHIC Beam Energy Scan-I. Outline:. Motivation Accessing QCD Phase Diagram: T and m B Searching QCD Phase Boundary: Turning-off QGP signatures Searching QCD critical point: Enhanced fluctuations BES Phase-II Summary.

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STAR Results from RHIC Beam Energy Scan-I

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  1. LokeshKumar (for STAR Collaboration) STAR Results from RHIC Beam Energy Scan-I Outline: • Motivation • Accessing QCD Phase Diagram: T and mB • Searching QCD Phase Boundary: Turning-off QGP signatures • Searching QCD critical point: Enhanced fluctuations • BES Phase-II • Summary Quark Matter 2012 August 12-18, 2012, Washington, DC Lokesh Kumar, QM2012

  2. STAR BES Program: Motivation QCD Phase Diagram: Main goals: • Study the QCD phase diagram: • Search for the signals of possible • phase boundary • Search for softening of EOS • Search for the possible QCD • Critical Point Important Steps: Proposal: Year 2008 Feasibility:Au+Au 9.2 GeV test run [STAR: PRC 81, 024911 (2010)] Year 2010: First phase started Year 2011: Two more energy points http://drupal.star.bnl.gov/STAR/starnotes/public/sn0493: arXiv:1007.2613 Lokesh Kumar, QM2012 2

  3. STAR Experiment EMC Barrel MRPC ToF Barrel EMC End Cap BBC HLT TPC PMD FTPC Au+Au 7.7 GeV Au+Au 200 GeV BES-I Data: Coverage: 0 < f < 2p |h| < 1.0 Uniform acceptance: All energies and particles p p pT (GeV/c) dNevt / (NevtdNch) p p Uncorrected Nch Rapidity Lokesh Kumar, QM2012 3

  4. Particle Identification PID (TPC+TOF): pion/kaon: pT~1.6 GeV/c proton pT~3.0 GeV/c Strange hadrons: decay topology & invariant mass TPC+TOF TPC Au+Au 39 GeV Lokesh Kumar, QM2012 4

  5. Two Considerations Changing energy in RHIC BES (higher to low √sNN) and look at the energy dependence trend of various observables RHIC BES Two perspectives: • Encounter varying net-baryon density • Change in baryon to meson ratio • 1st order phase transition effects • If lower energy only allows system • to enter hadronic phase • – Turn off of QGP signatures J. Randrup & J. Cleymans, Phys. Rev. C 74 (2006) 047901 In this talk: Discuss the observations seen from the data at RHIC BES in view of above two possibilities Lokesh Kumar, QM2012 5

  6. (A) Accessing Phase Diagram T-mB: From spectra and ratios Lokesh Kumar, QM2012 6

  7. p, K, p Spectra • Slopes: p > K > p • Proton spectra: • without feed-down • correction • p,K,p yields within • measured pT ranges: • 70-80% of total yields STAR Preliminary Lokesh Kumar, QM2012 7

  8. Strange Hadron Spectra K0s L X- Au+Au 39 GeV Au+Au 39 GeV Au+Au 39 GeV f, K0s: Levy function fit L, X : Boltzmann fit L: feed-down corrected STAR Preliminary STAR Preliminary Lokesh Kumar, QM2012

  9. Freeze-out Parameters S. Das: Fri, 6B Particles used: p, K, p, L, K0s, X THERMUS Model: Tch and mB STAR Preliminary • Centrality dependence of freeze-out • temperature with baryon chemical potential • observed for first time at lower energies Lokesh Kumar, QM2012

  10. Freeze-out Parameters Blast Wave: Tkinand <b> STAR Preliminary Particles used: p,K,p Au+Au STAR Preliminary S. Das: Fri, 6B • Higher kinetic temperature corresponds to lower value of average • flow velocity and vice-versa Lokesh Kumar, QM2012

  11. (B) Turn-OFF of QGP Signals/Softening of Equation of State/1st Order Phase Transition Dense medium (QGP) v1 vs. y: Rcp : NCQ Scaling: AMPT: Au+Au 9.2 GeV <px> (GeV/c) F. Liu et al., JPG 37094029 (2010) QGP? Turn-off of QGP? L.P.  Csernai et al., PLB  458,  454  (1999) K. Fukushima et al., PRD 78, 074033 (2008) 1st order phase tranisition? NCQ breaking in hadronic matter? Charge Separation: Lokesh Kumar, QM2012

  12. Directed Flow Y. Pandit: Tue, 1A STAR Preliminary v1 Mid-central collisions: Pion v1 slope: Always negative (7.7-39 GeV) (Net)-proton v1 slope: changes sign between 7.7 and 11.5 GeV Lokesh Kumar, QM2012

  13. Elliptic Flow STAR Preliminary Poster: A. Schmah #141 • Difference in baryon-antibaryon v2 • increases with decreasing √sNN: S. Shi: Fri, 6B baryon transport / hadronic interactions • - J. Dunlop et al., PRC 84, 044914 (2011) • - J. Xu et al., PRC 85, 041901 (2012) STAR Preliminary • For anti-particles: Baryons and mesons • show no splitting at 11.5 GeV STAR Preliminary • f-meson v2 deviates (~2s) from others • for √sNN ≤ 11.5 GeV: less collectivity • contribution from partonic interactions Lokesh Kumar, QM2012

  14. Dynamical Charge Correlations G. Wang: Thu, Plenary STAR Preliminary Splitting between same and opposite-sign charges: Decreases with decreasing √sNNand disappears below √sNN=11.5 GeV Lokesh Kumar, QM2012

  15. Rcp Measurements STAR Preliminary X. Zhang: Thu, 5A ForpT > 2 GeV/c: (Un)-Identified Rcp: • RCP (K0s) < 1 at √sNN > 19.6 GeV • RCP > 1 for √sNN ≤ 11.5 GeV E. Sangaline Thu, 5C Poster: S. Horvat # 94 Lokesh Kumar, QM2012

  16. Phase Boundary Search With Nuclei Strangeness Population Factor: Beam energy dependence of S3 behaves differently in QGP and pure hadron gas - S. Zhang et al., PLB 684 (2010) 224 - J. Steinheimer et al.,PLB 714 (2012) 85 Need higher statistics to make conclusive statement Y. Zhu: Thu, 5A Lokesh Kumar, QM2012

  17. observable Enhanced Fluctuations near Critical Point √s (C) Searching QCD Critical Point CO2near liquid-gas transition T. Andrews. Phil. Trans. Royal Soc., 159:575, 1869 • Particle ratio fluctuations (2nd moments) • - K/p, p/p, K/p • Conserved number fluctuations • - Higher moments of net-protons, net-charge,.. Lokesh Kumar, QM2012

  18. Particle Ratio Fluctuations K/p STAR Preliminary STAR Preliminary p/p STAR observed monotonic behavior for particle ratio fluctuations vs. √sNN STAR Preliminary P. Tribedy: Tue, 2C Poster: Z. Ahammed # 124 Lokesh Kumar, QM2012

  19. Higher Moments: Net-protons S  ~   • 0-5% central collisions: • Deviations below Poisson • observed for √sNN> 7.7 GeV • Peripheral collisions: • Deviations above Poisson • observed for √sNN< 19.6 GeV • Higher statistics needed • at 7.7 GeV and 11.5 GeV • and possibly a new data • point around ~15 GeV X. Luo: Fri, 7B Poster: Z. Li # 215 Lokesh Kumar, QM2012

  20. Higher Moments: Net-charge S  ~   STAR Preliminary • Data lies in between • Poisson and HRG model • expectations • Higher statistics needed • at 7.7 GeV and 11.5 GeV • and possibly a new data • point around ~15 GeV D. McDonald: Fri, 7B Posters: N. Sahoo # 557, A. Sarkar # 394 Lokesh Kumar, QM2012

  21. Beam Energy Scan Phase- II Lokesh Kumar, QM2012

  22. BES Phase-II proposal • Electron cooling will provide • increased luminosity ~ 10 times Proposal BES-II (Years 2015-2017): Fedotov, W. Fischer, private discussions, 2012. 1% Au target Fixed Target Proposal: Poster: B. Haag # 385 • Annular 1% gold target inside the STAR beam pipe • 2m away from the center of STAR • Data taking concurrently with collider mode at beginning of each fill : No disturbance to normal RHIC running Lokesh Kumar, QM2012

  23. STAR BESProgram Summary √sNN(GeV) Explore QCD Diagram 39 19.6 7.7 5 2.5 BES phase-I BES phase-II Fixed Target Test Run QGP properties 112 206 420 585 775 0 mB (MeV) Large range of mB in the phase diagram !!! Lokesh Kumar, QM2012

  24. Summary • Phase Diagram: • - Large mB range covered by the STAR in the phase diagram • - Centrality dependence of Tch vs. mB observed for the lower energies • Phase Boundary: • - Proton v1 slopechanges sign between 7.7 GeV and 11.5 GeV • - Particles-antiparticles v2 differenceincreases with decreasing √sNN • - f-meson v2 deviates from others for √sNN ≤ 11.5 GeV • - Dynamical charge correlations: vanish below 11.5 GeV • - Rcp > 1 for pT > 2 GeV/c and √sNN ≤ 11.5 GeV • Critical Point: • - Ratio fluctuations (2nd moment) show monotonic behavior vs. √sNN • - Deviation from Poisson observed for higher moments of net-protons • BES-II: • - Propose higher statistics data below 20 GeV • - Fixed target proposal to extend mB coverage up to 800 MeV Lokesh Kumar, QM2012

  25. Thanks to STAR Collaboration Thanks NIKHEF and Utrecht University, Amsterdam, The Netherlands Ohio State University, Columbus, Ohio 43210 Old Dominion University, Norfolk, VA, 23529 Panjab University, Chandigarh 160014, India Pennsylvania State University, University Park, Pennsylvania 16802 Institute of High Energy Physics, Protvino, Russia Purdue University, West Lafayette, Indiana 47907 Pusan National University, Pusan, Republic of Korea University of Rajasthan, Jaipur 302004, India Rice University, Houston, Texas 77251 Universidade de Sao Paulo, Sao Paulo, Brazil University of Science \& Technology of China, Hefei 230026, China Shandong University, Jinan, Shandong 250100, China Shanghai Institute of Applied Physics, Shanghai 201800, China SUBATECH, Nantes, France Texas A\&M University, College Station, Texas 77843 University of Texas, Austin, Texas 78712 University of Houston, Houston, TX, 77204 Tsinghua University, Beijing 100084, China United States Naval Academy, Annapolis, MD 21402 Valparaiso University, Valparaiso, Indiana 46383 Variable Energy Cyclotron Centre, Kolkata 700064, India Warsaw University of Technology, Warsaw, Poland University of Washington, Seattle, Washington 98195 Wayne State University, Detroit, Michigan 48201 Institute of Particle Physics, CCNU (HZNU), Wuhan 430079, China Yale University, New Haven, Connecticut 06520 University of Zagreb, Zagreb, HR-10002, Croatia Argonne National Laboratory, Argonne, Illinois 60439 Brookhaven National Laboratory, Upton, New York 11973 University of California, Berkeley, California 94720 University of California, Davis, California 95616 University of California, Los Angeles, California 90095 UniversidadeEstadual de Campinas, Sao Paulo, Brazil University of Illinois at Chicago, Chicago, Illinois 60607 Creighton University, Omaha, Nebraska 68178 Czech Technical University in Prague, FNSPE, Prague, 115 19, Czech Republic Nuclear Physics Institute AS CR, 250 68 \v{R}e\v{z}/Prague, Czech Republic University of Frankfurt, Frankfurt, Germany Institute of Physics, Bhubaneswar 751005, India Indian Institute of Technology, Mumbai, India Indiana University, Bloomington, Indiana 47408 Alikhanov Institute for Theoretical and Experimental Physics, Moscow, Russia University of Jammu, Jammu 180001, India Joint Institute for Nuclear Research, Dubna, 141 980, Russia Kent State University, Kent, Ohio 44242 University of Kentucky, Lexington, Kentucky, 40506-0055 Institute of Modern Physics, Lanzhou, China Lawrence Berkeley National Laboratory, Berkeley, California 94720 Massachusetts Institute of Technology, Cambridge, MA Max-Planck-Institutf\"urPhysik, Munich, Germany Michigan State University, East Lansing, Michigan 48824 Moscow Engineering Physics Institute, Moscow Russia Thank You Lokesh Kumar, QM2012

  26. BES Related Talks at QM2012 1). Beam Energy Dependence of Strange Hadron Production at RHIC: Xiaoping Zhang, Thu-5A, 15:00 2). Beam Energy Dependence of Hypertriton Production and Lifetime Measurement: Yuhui Zhu, Thu-5A:15:40 3). Centrality dependence of freeze-out parameters from the Beam Energy Scan at STAR: Sabita Das, Fri-6B:15:00 4). Di-electron production dependence on transverse momenta, reaction plane, centralities and collision energies in Au+Au collisions at STAR: Bingchu Huang, Wed-3C: 09:10 5). $R_{CP}$ and $R_{AA}$ Measurements of Identified and Unidentified Charged Particles at High $p_{T}$ in Au+Au Collisions at $\sqrt{s_{NN}}=$7.7, 11.5, 19.6, 27, 39, and 62.4 GeV in STAR: Evan Sangaline, Thu-5C: 15:00 6). Event anisotropy $v_2$ of charged and identified particles in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5, 19.6, 27, 39 and 62.4 GeV with STAR: Shusu Shi, Fri-6B: 15:20 7). Study of Net-proton High Order Cumulant in STAR at RHIC: Lizhu Chen, Tue-2C: 15:40 8). Search for the QCD Critical Point by Higher Moments of Net-proton Multiplicity Distributions at STAR: XiaofengLuo, Fri-7B: 17:30 9). Beam energy and centrality dependence of the statistical moments of the net-charge, net-kaon and total pion multiplicity distributions in Au+Au collisions at STAR: Daniel McDonald, Fri-7B: 16:50 10). Beam Energy Dependence of First and Higher-Order Flow Harmonics from the STAR Experiment at RHIC: YadavPandit, Tue-1A: 14:55 11). Search for QCD Phase Transitions and the Critical Point Utilizing Particle Ratio Fluctuations and Transverse Momentum Correlations from the STAR Experiment: PrithwishTribedy, Tue-2C: 16:45 12). Search for the Chiral Magnetic Effects in High-Energy Nuclear Collisions: Gang Wang, Thu-IVB: 12:20 13). Femptoscopy of identified particles at STAR: Neha Shah, Tue-1C: 14:35 Lokesh Kumar, QM2012

  27. BES Related Posters at QM2012 Lokesh Kumar, QM2012

  28. BES Related Posters at QM2012 Lokesh Kumar, QM2012

  29. Back up Lokesh Kumar, QM2012

  30. Chemical Freeze-out Statistical-Thermal Model (THERMUS): b=1/T; -1(+1) for fermions (bosons), Z=partition function; mi = mass of hadron species i; V = volume; T = Temperature; K2=2nd order Bessel function; gi = degeneracy; mi = chemical potential • Fitted particle ratios with THERMUS • Used grand-canonical approach • Two main parameters: Tch and mB Lokesh Kumar, QM2012

  31. Chemical Freeze-out Lokesh Kumar, QM2012

  32. Elliptic Flow Rate of increase of v2 is slow from 7.7-39 GeV Lokesh Kumar, QM2012

  33. Baryon-Meson Ratio STAR Preliminary Lokesh Kumar, QM2012

  34. C6/C2 L. Chen: Tue, 2C Lokesh Kumar, QM2012

  35. Fixed Target Set-up Lokesh Kumar, QM2012

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