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Review of Recent Heavy-Ion Results from RHIC

Lokesh Kumar. National Institute of Science Education and Research, Bhubaneswar. Review of Recent Heavy-Ion Results from RHIC. Outline:. Motivation QGP properties Beam energy scan: QCD phase diagram Summary. Triggering Discoveries in High Energy Physics

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Review of Recent Heavy-Ion Results from RHIC

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  1. LokeshKumar National Institute of Science Education and Research, Bhubaneswar Review of Recent Heavy-Ion Results from RHIC Outline: • Motivation • QGP properties • Beam energy scan: QCD phase diagram • Summary Triggering Discoveries in High Energy Physics September 9-14, 2013, University of Jammu, Jammu Lokesh Kumar, Jammu, Sep. 2013

  2. RHIC Heavy-ion Program Main goals: STAR: Nucl. Phys. A 757, 102 (2005) 1. Study QGP and its properties: - Detailed studies for temperature, viscosity, and energy density QCD Phase Diagram: • 2. Study QCD phase diagram: • Search for the signals of possible • phase boundary • - 1st order phase transition • Search for the possible QCD Critical • Point Beam Energy Scan http://drupal.star.bnl.gov/STAR/starnotes/public/sn0493: arXiv:1007.2613 Lokesh Kumar, Jammu, Sep. 2013 2

  3. (A) QGP study and properties Characterize QGP by measuring it’s properties such as: • Temperature • Energy density • Viscosity Lokesh Kumar, Jammu, Sep. 2013 3

  4. (I) Initial Temperature ii) Thermal radiation -- dominant at low pT -- information on initial temperature of QGP i) Initial hard scattering -- dominant at high pT -- information on PDFs, QCD, etc. Direct Photons: PHENIX : PRL,104,132301 (2010) ~ 3.5 - 7 X 1012oKelvin NLO pQCD calculations Tinitial > TC (Lattice) [~ 170 MeV] Low pT: Enhancement of direct photon yields in Au+Auw.r.t. p+p collisions Lokesh Kumar, Jammu, Sep. 2013 4

  5. (II) Suppression of high pThadron production A localized collection of hadrons which come from a fragmenting parton Jet: hadrons a c Behavior in pp and heavy-ion collisions: d b hadrons leading particle pp collisions: Unaffected Heavy-ions: Suppressed (if QGP) No. of binary collisions Jet Quenching: Suppression in production of high-pT particles in nucleus-nucleus collisions compared to corresponding data from binary collision scaled p+p collisions Measure: Nucelar Modification Factor (RAA/RCP) High pT: RAA/RCP < 1  QGP, RAA/RCP > 1  No QGP Lokesh Kumar, Jammu, Sep. 2013 5

  6. (II) Suppression of high pT hadron production B. Mohanty, New J.Phys.13, 065031 (2011) STAR: PRL 97, 152301 (2006); PLB 655, 104 (2007); PLB 637, 161 (2006). PHENIX: PRC 83,024909 (2011); PRC 82, 011902 (R) (2010); PRL 101, 232301 (2008); PRL 96, 202301 (2006). initial > c (Lattice ~1 GeV/fm3) • Large suppression of high pT meson • production in central Au+Au collisions • No suppression in d+Au experiment • Similar suppression in p, h and f: suppression is at partonic level • No suppression for direct photons: final state effect • Models assumption: initial ~ 5-15 GeV/fm3 Similar conclusion at LHC Lokesh Kumar, Jammu, Sep. 2013 6

  7. py px y z x anisotropy in momentum space initial spatial anisotropy Ellipticflow (III) Azimuthal Anisotropy Directedflow Lokesh Kumar 7

  8. baryons (III) Elliptic Flow: quarks Au+Au 200 GeV mesons STAR: PRL 95, 122301 (2005) nq = 2 for mesons, nq = 3 for baryons PHENIX: PRL 98, 162301 (2007) • Elliptic flow scaled by number of constituent quarks (NCQ) follow • a common curve for different particles – NCQ scaling • Flow develops at the partonic level (indication of QGP formation) Lokesh Kumar

  9. (III) Elliptic Flow: Shear viscosity to entropy density (h/s): A. Tang, NPA 830, 673C (2009) RHIC 1/4p – (10*1/4p) Similar h/s at RHIC and LHC LHC 1/4p – (4*1/4p) Roy et al., JPG: NPP 40, 065103 (2013) Roy et al., PRC 86, 014902 (2012) Lokesh Kumar

  10. QGP Properties: Conclusions RHIC has established the formation of QGP: hot and dense Some of the properties: Lokesh Kumar

  11. (B) Beam Energy Scan i) Search for the signals of possible phase boundary ii) First order phase transition/ softening of equation of state ii) Search for the possible QCD Critical Point BES-I Data (STAR): USA-NSAC 2007, Long-range plan Lokesh Kumar, Jammu, Sep. 2013 11

  12. (I) Accessing Phase Diagram T-mB: From pTspectra and ratios crossover Lokesh Kumar 12

  13. Freeze-out Parameters Statistical-Thermal Model (THERMUS): b=1/T; -1 (+1) for fermion(boson) Z=partition function; mi = mass of hadron species i; V = volume; T = Temperature; K2=2nd order Bessel function; gi = degeneracy; mi = chemical potential Particles used: p, K, p, L, K0s, X Two main parameters: Tch and mB Centrality dependence of freeze-out temperature with baryon chemical potential observed for first time at lower energies Lokesh Kumar

  14. (II) Turn-OFF of QGP Signals/Softening of Equation of State/1st Order Phase Transition • Net-proton Directed Flow (1st-order phase transition) • Elliptic Flow (Turn-off of QGP signatures) • Charge Separation w.r.t. Reaction Plane (Turn-off of QGP) • Nuclear Modification Factor (Turn-off of QGP signatures) Lokesh Kumar

  15. Directed Flow: H. Stoecker, NP A750, 121 (2005). “collapse” of proton v1 in 3-fluid hydro with 1st-order phase transition Fp = r Fanti-p + (1 – r) Fnet-p, r is the observed ratio of antiprotons to protons. Pion v1 slope: Always negative (7.7-39 GeV) (Net)-proton v1 slope: changes sign between 7.7 and 11.5 GeV (shows a minimum at ~ 19.6 GeV) Lokesh Kumar

  16. Elliptic Flow: STAR: PRL 110, 0142301 (2013) • Difference in baryon-antibaryon v2 • increases with decreasing √sNN: baryon transport / hadronic interactions • - J. Dunlop et al., PRC 84, 044914 (2011) • - J. Xu et al., PRC 85, 041901 (2012) • For anti-particles: Baryons and mesons • show no splitting at 11.5 GeV • f-meson v2 deviates (~2s) from others • for √sNN ≤ 11.5 GeV: less collectivity • contribution from partonic interactions Lokesh Kumar

  17. Dynamical Charge Correlations • De-confined state (QGP): parity may • be locally-violated • Strong magnetic field, may lead to • separation of charges along the angular • momentum vector • ChiralMagnetic Effect (CME) Charge separation w.r.t reaction plane Lokesh Kumar

  18. Dynamical Charge Correlations STAR Preliminary Splitting between same and opposite-sign charges: Decreases with decreasing √sNNand disappears below √sNN=11.5 GeV Lokesh Kumar

  19. Rcp Measurements ForpT > 2 GeV/c: • RCP (K0s) ≤ 1 at √sNN ≥ 19.6 GeV • RCP > 1 for √sNN ≤ 11.5 GeV Lokesh Kumar

  20. What we learnt? Hadronic interactions dominate at √sNN ≤ 11. 5 GeV Lokesh Kumar

  21. Enhanced fluctuations near critical point: Non-monotonic behavior observable √s (III) Search QCD Critical Point CO2near liquid-gas transition T. Andrews. Phil. Trans. Royal Soc., 159:575, 1869 Conserved number fluctuations - Higher moments of net-protons, net-charge,.. Lokesh Kumar

  22. Higher Moments: Net-protons Typical net-proton distribution: Various moments: Correlation length: ~ x2 Sigma: ~ x4.5 Skewness: Kurtosis: ~ x7 M. Stephanov, PRL 107, 052301 (2011) M. Stephanov, PRL 102, 032301 (2009) Products of moments related to baryon number susceptibility: R. Gavai et al. PLB 696, 459 (2011) S  ~  R. Cheng et al. PRD 79, 074505 (2009)  (Volume effect is cancelled) STAR: PRL105, 022302 (2010) Experimental measurements can be related to lattice QCD observables for critical point search Lokesh Kumar

  23. Higher Moments: Net-protons S  ~   • Poisson may act as a baseline • => No critical point • Deviation from Poisson • => Possible critical point • Other baselines: (N)BD, random sampling between p and pbar • Hints of deviation from Poisson • Need higher statistics at low • energies Similar conclusions for net-charge results Data: efficiency uncorrected Lokesh Kumar

  24. Summary :RHIC Heavy-ionProgram QGP properties: √sNN(GeV) BES Program: Explore QCD phase diagram 39 19.6 7.7 5 2.5 BES phase-I BES phase-II Fixed Target Test Run QGP properties BES program: - Hadronic interactions dominate at √sNN≤ 11.5 GeV - BES-II: Higher statistics at √sNN< 20 GeV 112 206 420 - Fixed Target: Higher mB 585 775 0 mB (MeV) Large range of mB in phase diagram !!! Lokesh Kumar, Jammu, Sep. 2013

  25. Thank You Lokesh Kumar, Jammu, Sep. 2013

  26. Back up Lokesh Kumar, Jammu, Sep. 2013

  27. BES Phase-II proposal Proposal BES-II (Year ~ ≥ 2017): • Electron cooling will provide • increased luminosity ~ 10 times Fedotov, W. Fischer, C-AD/BNL cooling No cooling 1% Au target Fixed Target Proposal: iTPC Upgrade: • Gold (Au) target inside the STAR • beam pipe (~2m away from center) • Data taking will be done concurrently • with collider mode - Improved acceptance: higher h (|h|< 1.7) and low pT (~ 100 MeV/c) reach - Improved dE/dx and efficiency : No disturbance to normal RHIC running Lokesh Kumar

  28. Outlook – Fixed Target STAR Fixed-Target Run14 Set-up • Fixed-Target Trigger: • BBC-East • Not-BBC-West • TOFmult >70 • top 30% centrality Au+Au • 106Au+Al rejection Place fixed target here (z ~ 2.0 m) Tof h = 1.0 h = 0.5 h = 0 h=1.5 Mid-rapidity for 4.5 GeV BBC-East BBC-West h = 2.0 This Slide just defines the geometry and indicates where the target would be located Yellow Beam Gold Segment 30 mil thick FGT will not be installed for run 14 Al Beam Pipe 4.0 cm diameter Be Beam Pipe Al Beam Pipe VPD-East Beam pipe and Target Schematic Energies for Run14

  29. Fixed Target Set-up Fixed Target Collisions * J. Cleymans, H. Oeschler, K. Redlich, S. Wheaton, PR C73, 034905 (2006). • We have now put forward a BES-II proposal to focus on the most interesting region • Electron cooling is key to the feasibility of this proposal • eCooling will take a few years • Expect BES-II in 2017-2019 SRF Cavity BES-II Lokesh Kumar, Jammu, Sep. 2013

  30. Timeline: STAR Lokesh Kumar, Jammu, Sep. 2013

  31. Chemical Freeze-out Lokesh Kumar, Jammu, Sep. 2013

  32. Elliptic Flow Rate of increase of v2 is slow from 7.7-39 GeV Lokesh Kumar, Jammu, Sep. 2013

  33. Baryon-Meson Ratio STAR Preliminary Lokesh Kumar, Jammu, Sep. 2013

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