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

  7. … and how was it discovered

  8. 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

  9. 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

  10. …and at LHC … ALICE, Phys.Lett. B696 (2011)30

  11. …and compared to pA reference arXiv:1210.4520v1

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

  13. 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

  14. 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.

  15. … 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

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

  17. v2(pT): LHC vs. RHIC ALICE: PRL 105 (2010) 252302 The same flow properties from √sNN=200 GeV to 2.76 TeV

  18. 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

  19. 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

  20. The RHIC Beam Energy Scan Project • Since the original design of RHIC (1985), running at lower energies has been envisioned. • Possibilities of RHIC running at lower energies were studied with a series of test runs: 19.6 GeV Au+Au in 2001, 22.4 GeV Cu+Cu in 2005, and 9.2 GeV Au+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. QGP Turn-off First Order Cross-Over Critical Point First Order Phase Transition

  21. Selected Results

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

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

  24. 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:

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

  26. <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)

  27. 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

  28. 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

  29. 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

  30. 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.

  31. 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

  32. 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

  33. 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)]

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

  35. 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

  36. 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

  37. 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.

  38. 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

  39. Overview of the BES I Results • Turn-off of QGP signatures: • NCQ breaks down below 19.6 GeV • High pt suppression not seen below 19.6 GeV • LPV effect not seen below 11.5 GeV • Evidence of the first order phase transition. • v1 sign change above 7.7 • Inflection in v2 and dET/dh at 7.7 • Azimuthal HBT signal inconclusive • Search for the critical point. • K/p, K/p, or p/p fluctuations are not conclusive. • Higher moments of the proton distributions Clear Evidence Strong Hints Hints Daniel Cebra @ APS DNP Meeting – Town Meeting Newport Beach, CA, 10/26/2012

  40. Beam Energy Scan Phase- II

  41. Beam Energy Scan II Add a week between each energy, and BES II program will take about 17 weeks • BES II will focus on the most interesting regions of the phase diagram • Electron cooling is key to the feasibility of this program; without cooling, BES II would take ~70 weeks BES II Daniel Cebra @ APS DNP Meeting – Town Meeting Newport Beach, CA, 10/26/2012

  42. BES Phase-II proposal • Electron cooling will provide • increased luminosity ~ 10 times Proposal BES-II (Years 2015-2017): Fedotov, W. Fischer, private discussions, 2012. At current rates, this would take ~70 weeks of RHIC operations! Isn’t there a better way?  Yes! We can cool the beams!

  43. 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

  44. Fixed Target Set-up

  45. 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 !!!

  46. Timeline for RHIC’s Next Decade

  47. The Alternatives Is there another way? Can another facility do this faster? Or better?

  48. Super Proton Synchrotron (SPS) Runn + Running now, that’s good + Energy range is good - But fixed-target - And light ions Not Ideal • Time Line: 2009-2015 • Energy Range: √sNN=4.9 - 17.3 GeV • mB= 0.560 - 0.230 GeV BES I Daniel Cebra @ APS DNP Meeting – Town Meeting Newport Beach, CA, 10/26/2012

  49. Nuclotron based Ion Collider fAcility (NICA) • Time Line: Not yet funded. Plan is to submit documents by end of 2012. Operations could not begin before 2017 (probably much later) • Energy Range: √sNN= 3.9 - 11 GeV for Au+Au; mB=0.630 - 0.325 GeV. • + Collider, that’good • + High Luminosity expected • MPD simiar to STAR • Maybe as early as 2017 • - (But probably later) • Energy is too low! • Will miss the critical point Multi-Purpose Detector (MPD) Daniel Cebra @ APS DNP Meeting – Town Meeting Newport Beach, CA, 10/26/2012

  50. Facility for Antiproton and Ion Research (FAIR) Energy Range: SIS-100: Au+Au @ √sNN=2.9 GeV SIS-300: Au+Au√sNN= 2.7 - 8.2 GeV mB=0.730 - 0.410 GeV Time Line: SIS-100 is funded and will be complete by 2018 SIS-300 will need additional funding (no time estimate) • ++ Very High Interaction Rate • Fixed target geometry • - No time estimate for SIS-300 • Probably after 2022 • Even with SIS-300, the energy is too low! • Will miss the critical point Compressed Baryonic Matter (CBM) ECAL TOF TRD RICH MVD STS Daniel Cebra @ APS DNP Meeting – Town Meeting Newport Beach, CA, 10/26/2012

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