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Beam Energy Scan Program at RHIC

Beam Energy Scan Program at RHIC . Michal Šumbera Nuclear Physics Institute AS CR, Řež / Prague. PHOBOS. BRAHMS. RHIC. PHENIX. STAR. AGS. TANDEMS. R elativistic H eavy I on C ollider Brookhaven National Laboratory (BNL), Upton, NY. Animation M. Lisa.

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Beam Energy Scan Program at RHIC

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  1. Beam Energy Scan Program at RHIC Michal Šumbera Nuclear Physics Institute AS CR, Řež/Prague

  2. PHOBOS BRAHMS RHIC PHENIX STAR AGS TANDEMS Relativistic Heavy Ion ColliderBrookhaven National Laboratory (BNL), Upton, NY Animation M. Lisa World’s (second) largest operational heavy-ion collider World’s largest polarized proton collider

  3. Recorded Datasets Fast DAQ + Electron Based Ion Source + 3D Stochastic cooling

  4. Remarkable discoveries at RHIC • Perfect liquid BRAHMS, PHENIX, PHOBOS, STAR, Nuclear Physics A757 (2005)1-283 • Number of constituent quark scaling PHENIX, PRL 91(2003)072301; STAR, PR C70(2005) 014904 • Jet quenching PHENIX, PRL 88(2002)022301; STAR, PRL 90(2003) 082302 • Heavy-quark suppressionPHENIX, PRL 98(2007)172301, STAR, PRL 98(2007)192301 • Production of exotic systems • Discovery on anti-strange nucleusSTAR, Science 328 (2010) 58 • Observation of anti-4He nucleusSTAR, Nature 473 (2011) 353 • Indications of gluon saturation at small xSTAR, PRL 90(2003) 082302; BRAHMS, PRL 91(2003) 072305; PHENIX ibid 072303

  5. Introducing sQGP …

  6. Festschrift in honor of B.L. Ioffe,”At the Frontier of Particle Physics / Handbook of QCD”, M. Shifman, ed., (World Scientific).

  7. QCD Phase Diagram Crossover ~21012K 1st/2nd order  Particle Physics

  8. … and how was it discovered

  9. leading particle suppressed hadrons q q ? Scaling AA to pp (or central to peripheral) Phys.Lett.B243 (1990)432 FERMILAB- Pub-82/59-THY Nucleus-nucleus yield <Nbinary>/sinelp+p NULL Result AA If R = 1 here, nothing “new” is going on

  10. Suppresion of leading hadrons at RHIC Au + Au Experiment d + Au Control Experiment • Dramatically different and opposite centrality evolution of Au+Au experiment from d+Au control experiment. • New state of matter is produced in central Au+Au collisions at √sNN=200GeV

  11. …and at LHC arXiv:1210.4520v1

  12. Single hadron RAA: RHIC vs LHC RAA RAA for both systems looks similar

  13. …and at LHC For pT < 8 GeV/c: RAA for p and K are compatible and they are smaller than RAA for proton. For pT> 10 GeV/c: the RAA for p, K and proton are compatible within systematic error.

  14. LHC: Suppression of inclusive jets CMS-PAS HIN-12-004 Fully unfolded inclusive jet RAA pp 2.76 TeV reference Like for charged particles, high-pT jet RAA flat at ≈ 0.5

  15. Dihadronazimuthal correlations at RHIC STAR, PRL 90(2003) 082302 Azimuthal distribution of hadrons with pT > 2 GeV/c relative to trigger hadron with pTtrig > 4 GeV/c (background subtracted). Data are from p+p, central d+Au and central Au+Au collisions.

  16. … and g+jet at LHC Photon (191GeV) Jet (98 GeV) • Photon tag: • Identifies jet as u,d quark jet • Provides initial quark direction • Provides initial quark pT

  17. Elliptic flow: off-plane or in-plane v2 < 0: for 100 AMeV ≤ Ebeam ≤ 5 AGev slowly moving spectator matter prevents the in-plane emission of participating nucleons or produced pions which appear to be sqeezed-out of the reaction zone W. Greiner & Co. PRC 25 (1982) 1873 J.-Y. Ollitrault PRD 46 (1992) 229, PRD 48 (1993) 1132 v2 > 0: at higher energies shadowing disappears and interactions among produced particles generate in-plane emission

  18. y  2v2 dN/df dN/df 0  2p 0 f 2p Elliptic Flow and Collectivity Pressure gradient Initial spatial anisotropy x INPUT Spatial Anisotropy Interaction among produced particles OUTPUT Momentum Anisotropy  Free Streaming v2 = 0

  19. Energy Dependence of Elliptic Flow ALICE: PRL 105 (2010) 252302

  20. V2(pT): LHC vs.RHIC ALICE: PRL 105 (2010) 252302 The same flow properties from √sNN=200 GeV to 2.76 TeV

  21. The ‘Standard Model’ of high energy heavy ion collisions 1) Quenching All hard hadronic process are strongly quenched 2) Flow Pantarhei: All soft particles emerge from the common flow field

  22. Why to go to lower energies? • 0) Turn-off of sQGP signatures • 1) Search for the signals of phase boundary • 2) Search for the QCD critical point

  23. The RHIC Beam Energy Scan Project • Since the original design of RHIC (1985), running at lower energies has been envisioned • RHIC has studied the possibilities of running lower energies with a series of test runs: 19.6 GeVAu+Au in 2001, 22.4 GeVCu+Cu in 2005, and 9.2 GeVAu+Au in 2008 • In 2009 the RHIC PAC approved a proposal to run a series of six energies to search for the critical point and the onset of deconfinement. • These energies were run during the 2010 and 2011 running periods. Alandmark of the QCD phase diagram

  24. Selected Results

  25. RAAof neutral pions

  26. RAA(pT)of neutral pions

  27. RAA(pT)of neutral pions

  28. Suppression of Charged Hadrons … PRL 91, 172302 (2003) (0-5%/60-80%) STAR Preliminary

  29. … and its Disappearance PRL 91, 172302 (2003) (0-5%/60-80%) STAR Preliminary RCP ≥ 1 at √sNN ≤ 27 GeV- Cronin effect?

  30. RCP: Identified Particles STAR Preliminary • Baryon-meson splitting reduces and disappears with decreasing energy • RCP (K0s) < 1 @√sNN > 19.6 GeV • RCP > 1 @ √sNN ≤ 11.5 GeV ForpT > 2 GeV/c:

  31. Baryon/Meson Ratio STAR Preliminary • W/f ratio falls off at 11.5 GeV

  32. <px> or directed flow rapidity Directed flow is quantified by the first harmonic: Azimuthal Anisothropy • Directed flow is due to the sideward motion of the particles within the reaction plane. • Generated already during the nuclear passage time (2R/g≈.1 fm/c@200GeV) • It probes the onset of bulk collective dynamics during thermalization v1(y) is sensitive to baryon transport, space - momentum correlations and QGP formation (preequilibrium)

  33. Directed Flow of p and π p π 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 - may be due to the contribution from the transported protons coming to midrapidity at the lower beam energies

  34. Energy Dependence of v2 STAR, ALICE: v2{4} results Centrality: 20-30% ALICE: PRL 105, 252302 (2010) PHENIX: PRL 98, 162301 (2007) PHOBOS: PRL 98, 242302 (2007) CERES: Nucl. Phys. A 698, 253c (2002). E877: Nucl. Phys. A 638, 3c(1998). E895: PRL 83, 1295 (1999). STAR 130 Gev: Phys.Rev. C66,034904 (2002). STAR 200 GeV: Phys.Rev. C72,014904 (2005). STAR Preliminary • The rate of increase with collision energy is slower from 7.7 to 39 GeV compared to that between 3 to 7.7 GeV

  35. v2(pT): First Result STAR: Nucl.Phys. A862-863(2011)125 • v2 (7.7 GeV) < v2 (11.5 GeV) < v2 (39 GeV) • v2 (39 GeV) ≈ v2 (62.4 GeV) ≈ v2 (200 GeV) ≈ v2 (2.76 TeV) • sQGP from 39 GeVto 2.76 TeV

  36. v2(pT): Final Result STAR Coll.: e-Print arXiv:1206.5528 ALICE data: PRL 105, 252302 (2010) For pT< 2 GeV/c: v2 values rise with increasing √sNN For pT ≥ 2 GeV/c: v2 values are (within stat. errors) comparable The increase of v2 with √sNN,could be due to change of chemical composition and/or larger collectivity at higher collision energy.

  37. v2 vs. mT-m0 STAR Preliminary Corresponding anti-particles Particles • Baryon–meson splitting is observed when collisions energy ≥ 19.6 GeV • for both particles and the corresponding anti-particles • For anti-particles the splitting is almost gone within errors at 11.5 GeV

  38. Particles vs. Anti-particles • Beam energy ≥ 39 GeV • Δv2 for baryon and anti-baryon • within 10% • Almost no difference for mesons • Beam energy < 39 GeV • The difference of baryon and anti-baryon v2 • →Increasing with decrease of beam energy • At √sNN= 7.7 - 19.6 GeV • v2(K+)>v2(K-) • v2(π-) >v2(π+) • Possible explanation(s) • Baryon transport to midrapidity? • ref: J. Dunlop et al., PRC 84, 044914 (2011) • Hadronic potential? • ref: J. Xu et al., PRC 85, 041901 (2012) STAR Preliminary The difference between particles and anti-particles is observed

  39. NCQ Scaling Test Particles STAR Preliminary • Universal trend for most of particles – ncq scaling not broken at low energies • ϕmeson v2 deviates from other particles in Au+Au@(11.5 & 7.7) GeV: ~ 2σ at the highest pTdata point Reduction of v2forϕmesonand absence of ncq scaling during the evolution the system remains in the hadronic phase [B. Mohanty and N. Xu: J. Phys. G 36, 064022(2009)]

  40. Accessing Phase Diagram T-mB: From spectra and ratios

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

  42. 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

  43. Chemical Freeze-out Parameters THERMUS* Model: Tch and mB Particles used: p, K, p, L, K0s, X STAR Preliminary • Centrality dependence of freeze-out • temperature with baryon chemical potential • observed for first time at lower energies • S. Wheaton & J.Cleymans, Comp. Phys. Com. 180: 84, 2009.

  44. Kinetic Freeze-out Parameters Blast Wave: Tkinand <b> STAR Preliminary Particles used: p,K,p Au+Au STAR Preliminary • Higher kinetic temperature corresponds to lower value of average • flow velocity and vice-versa

  45. Beam Energy Scan Phase- II

  46. 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: • 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

  47. Fixed Target Set-up

  48. BES Program 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 !!!

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