Strongly Coupled Plasma: Properties and Critical Point Search - PowerPoint PPT Presentation

Strongly Coupled Plasma: Properties and Critical Point Search Barbara Jacak, Stony Brook October 4, 2010 ICFA Seminar, CERN

Why Quark Gluon Plasma?  QCD predicts: @ high T color screening reduces confining potential  T c ~ 155 MeV  Asymptotic freedom in the medium? PRD75:054504(2007) pQCD (particles) AdS/CFT (fields) 2 2  3,3  2,n  2…

Explore the region near T c SPS at CERN Relativistic Heavy Ion Collider at Brookhaven 3

g dir shows T initial > T c at RHIC 4  Exponential fit p T spectrum slope = 221 ±23 ±18 MeV  Hydrodynamics reproduces g ’s; vary thermalization time PRL104, 132301, T init ≥ 300 MeV, t < 1 fm/c PRC81, 034911 (2010) 4

Bulk matter flows collectively STAR PRL98, 162301 (2007) h/ s=0.08 Fourier analyze particle emission pattern arXiv:1109.6289  Hydrodynamic flow of hadrons @ p T < 2 GeV/c Nearly ideal hydro flow! h /s near quantum bound 1/(4 )   Thermalization in < 1 fm/c Low h /s  good momentum transport  strong coupling  How can equilibration be achieved so rapidly?  Flow scales with # of valence quarks  What are the initial conditions?  Are there quasiparticles in the quark gluon plasma? 5 If so, when and what are they?

Plasma is very opaque AA/N coll *pp  Colored particles suffer large energy loss  opaque up to high p T A challenge for pQCD (g radiation dominated) Radiation + collisional energy loss?  At what scales (distance, E, M) is coupling strong?  What mechanisms for parton-plasma interactions? For plasma response? 6

Even heavy quarks lose energy & flow! arXiv:1109.5738 heavy quark diffusion 2  DT pQCD x 25% N eB /(N eB +N eD ) Quenched lQCD  arXiv:1005.1627  At what scales (distance, E, M) is the coupling strong?  What is the parton-plasma interaction? Is there a plasma response? added evidence for  Are there quasiparticles? 7 strong coupling!

J/ y : color screening in QGP? AA/N coll *pp arXiv:1103.6269  No obvious suppression pattern with e , T! SPS J/ y  Final state recombination suppression plays a √ s dependent role  To understand color screening: study as a function of √ s, p T , r onium  NB: need d+Au data to disentangle cold matter effects in initial state 8

Effect of final state cc coalescence? Open charm flows but J/ y does not  c-cbar coalescence @ RHIC is not large Correlations remain in QGP due to strong coupling? Need ϒ 1S, 2S, 3S  Is there a relevant color screening length? 9

New questions from RHIC & LHC data! 1. At what scales is the coupling strong? 2. What is the mechanism for quark/gluon- plasma interactions? Plasma response? Is collisional energy loss significant? 3. Are there quasiparticles in the quark gluon plasma? If so, when and what are they? 4. Is there a relevant (color) screening length? 5. How is thermalization achieved so rapidly? 6. Are there novel symmetry properties? 7. Nature of QCD matter at low T but high  ? (i.e. what is the initial state?) 10

To answer these questions 11

Upgrade PHENIX to answer the questions 12 Compact, hermetic, EM + hadron calorimetry

Use RHIC’s key capabilities*  Coupling scale & quasiparticle search charm hard(not thermal) probe @ RHIC c vs. b in QGP  parton-plasma interaction Jets ≤ 50 GeV, g -jet Au+Au E jet , l , q mass , angle dep. of dE/dx Cu+Au Jet virtuality ~ medium scale U+U  Screening length study as function of √ s, p T , r onium  Thermalization mechanism rare probe scan: g dir yield, spectra & flow 50< √ s <200 GeV &  QCD in cold, dense (initial) state asymmetric systems y dependence in d+Au Luminosity x10 at RHIC Gluon saturation scale? Large acceptance in both 13 EIC *In the era of Pb+Pb at the LHC STAR & PHENIX

Can we locate the QCD critical point? S. Gupta, QM2011 14

Fluctuations as Critical Point Signature Karsch, et al. PLB695 2010.10046 Event-by-event net-baryon fluctuation ratios from STAR are so far consistent with the Hadron Resonance Gas Hadron freezeout not (yet) near critical point Calculations of higher moments from LQCD deviate from HRG calculations and may provide conclusive 15 evidence for critical point if observed in data

Beam Energy Scan Plans RHIC (Au+Au) √s NN Status Experiment (GeV) SPS 5.0 TBD STAR species Status year STAR 7.7 analyzed PHENIX (limited p+p done 2009-2011 statistics) 11.5 analyzed STAR Be + Be Next for NA61 2011-2012 Collected in Ar + Ca NA61 2014 19.6 STAR, PHENIX 2011 Xe + La NA61 2015 Collected in 27 STAR, PHENIX Pb + Pb NA49 did 1996-2002 2011 p+Pb 2012/2014 39 analyzed STAR, PHENIX 62 analyzed STAR, PHENIX SPS scan: collected in 13, 20, 30, 40, 80, 158 GeV/A Run-1, analyzed 130 STAR, PHENIX Search also for onset of limited statistics deconfinement 16

Rapid thermalization?  Parton cascade is simply not fast enough  A number of cool, inventive ideas Plasma instabilities? arXiv:1011.3562 v. strong coupling (holographic) -> hydro valid after 3 sheet thicknesses! Shatter a color glass condensate?  A paucity of predicted experimental observables Needs more theory work  Understanding the initial state (cold gluonic matter) is key 17

Electron-ion collider; e-p collider 10x100 Gluon momentum fraction  helicity Existing e+p range 0.4 Existing p+p range Current best fit Current fit uncertainty distribution Uncertainty w/ EIC 0.2 0 18 10  5 10  4 10  3 10  2 10  1 1 Inferred momentum fraction of sampled gluons

RHIC’s future - hot and exciting  Near-term (2011-2016) Stochastic cooling  4 x 10 27 ; Cu+Au New microvertex detectors for heavy quark probes Quantify properties of near-perfect fluid QGP (v n ) Quantify features of the QCD phase diagram Study novel symmetries, exotic particles  Medium-term (2017-2022) Upgraded detectors Upgrade PHENIX: compact, large acceptance jet, quarkonia, photon detector Add forward spectrometer, muon telescope to STAR Attack the list of new QGP questions Study parton transverse spin in polarized p+p  Long- term (≥ 2023) Electron -Ion Collider Add ~5 GeV (upgradable to 30 GeV) electron Energy Recovery Linac inside RHIC tunnel e+A, e+p ( 3 He) for GPDs, D g, gluonic cold matter 19

 Backup 20

Many types of strongly coupled matter Quark gluon plasma is like other systems with strong coupling - all flow and exhibit phase transitions Cold atoms: coldest & hottest matter on earth are alike! Dusty plasmas & warm, dense plasmas Strongly correlated have liquid and even condensed matter: crystalline phases liquid crystal In all these cases have a competition: phases and Attractive forces  repulsive force or kinetic energy superconductors Result: many-body interactions; quasiparticles exist? 21

Properties of hot QCD matter?  thermodynamic (equilibrium) T, P,  Equation Of State (relation btwn T, P, V, energy density) v sound , static screening length  transport properties (non-equilibrium)* particle number, energy, momentum, charge diffusion sound viscosity conductivity In plasma: interactions among charges of multiple particles charge is spread, screened in characteristic (Debye) length, l D also the case for strong, rather than EM force *measuring these is new for nuclear/particle physics! Nature is nasty to us: does a time integral… 22

Measuring collective flow: start with v 2 Almond shape overlap region in coordinate z space y x momentum space dN/d f ~ 1 + 2 v 2 (p T ) cos (2 f ) + … “elliptic flow” 23

Quantify the viscosity v n (h/ s=0.08)/v n (ideal) v n (h/ s=0.16)/v n (ideal) h arXiv:1109.6289  Viscosity/entropy ratio near quantum bound 1/(4 )  Low viscosity/entropy  very good momentum transport  strong coupling  At what scales is the coupling strong?  What are the initial conditions? 24

Can we locate the QCD critical point? + deconfinement onset S. Gupta, 25 QM2011

Early hard probe insights from LHC  Quarkonia energy dependence not understood! Need charmonium and bottonium states at >1 √ s at RHIC + guidance from lattice QCD!  Jet results from LHC very surprising! Steep path length dependence of energy loss also suggested by PHENIX high p T v 2 ; AdS/CFT is right? Unmodified fragmentation function of reconstructed jets looks different at RHIC, depends on “jet” definition? Lost energy goes to low p T particles at large angle is dissipation slower at RHIC? Due to medium or probe? Little modification of di-jet angular correlation appears to be similar at RHIC  Need full, calorimetric reconstruction of jets in wide y range at RHIC to disentangle probe effects/medium 26 effects/initial state

Is there a relevant screening length? Lattice: Karsch, et al. running coupling  Strongly coupled matter: few particles in Debye sphere - decreases screening! coupling drops off for r > 0.3 fm Ding, et al. arXiV: 1107.0311 LQCD spectral functions show correlation remaining at T>T c 27 Partial screening?

Need to understand quantitatively!  Coalescence could be important at LHC More c-cbar pairs produced. Use b- bar to probe… ϒ (2S,3S) suppressed  Does partial screening preserve correlations, enhancing likelihood of final state coalescence?  arXiV:1010.2735 (Aarts, et al):  unchanged to 2.09T c c b modified @ 1-1.5T c , then free. Need  states at 28 RHIC!