STAR 1 Warsaw STAR/ALICE HBT Workshop - May malisa Dynamics at low and high p T from the Solenoidal Tracker At RHIC (STAR) Mike Lisa, Ohio State University STAR Collaboration U.S. Labs: Argonne, Lawrence Berkeley National Lab, Brookhaven National Lab U.S. Universities: Arkansas, UC Berkeley, UC Davis, UCLA, Carnegie Mellon, Creighton, Indiana, Kent State, Michigan State, CCNY, Ohio State, Penn State, Purdue, Rice, Texas A&M, UT Austin, Washington, Wayne State, Yale Brazil: Universidade de Sao Paolo China: IHEP - Beijing, IPP - Wuhan England: University of Birmingham France: Institut de Recherches Subatomiques Strasbourg, SUBATECH - Nantes Germany: Max Planck Institute – Munich, University of Frankfurt Poland: Warsaw University, Warsaw University of Technology Russia: MEPHI – Moscow, LPP/LHE JINR–Dubna, IHEP-Protvino

STAR 2 Warsaw STAR/ALICE HBT Workshop - May malisa Outline General goal of RHIC physics RHIC & STAR  hadro-chemistry driving dynamical physics and consistent low p T ? –central collisions  radial flow two-particle correlations   HBT  K-  correlations  balance functions –non-central collisions  elliptical flow  HBT vs reaction-plane –low-p T summary driving “high” p T ?  spectra compared to pp collisions  momentum-space anisotropy  two-particle correlations Summary starting slow & ending fast

STAR 3 Warsaw STAR/ALICE HBT Workshop - May malisa Why heavy ion collisions? Study bulk properties of nuclear matter The “little bang” Extreme conditions (high density/temperature) expect a transition to new phase of matter… Quark-Gluon Plasma (QGP) partons are relevant degrees of freedom over large length scales (deconfined state) believed to define universe until ~  s Heavy ion collisions ( “little bang”) the only way to experimentally probe deconfined state Study of QGP crucial to understanding QCD low-q (nonperturbative) behaviour confinement (defining property of QCD) nature of phase transition

STAR 4 Warsaw STAR/ALICE HBT Workshop - May malisa The “little bang” Stages of the collision pre-equilibrium (deposition of initial energy) rapid (~1 fm/c) thermalization (?) high-p T observables probe this stage QGP formation (?) hadronic rescattering hadronization transition (very poorly understood) Chemical freeze-out: end of inelastic scatterings Kinetic freeze-out: end of randomizig scatterings low-p T hadronic observables probe this stage “end result” looks very similar whether a QGP was formed or not!!! time temperature

STAR 5 Warsaw STAR/ALICE HBT Workshop - May malisa The “little bang” Stages of the collision time temperature Experimentally calibrating time, temperature “axes” critical to gaining insight into physics of extreme nuclear conditions provides a stringent test of dynamical models

STAR 6 Warsaw STAR/ALICE HBT Workshop - May malisa Already producing QGP at lower energy? J. Stachel, Quark Matter ‘99 Thermal model fits to particle yields (including strangeness, J/  )  approach QGP at CERN? is the system really thermal? warning: e + e - falls on similar line!! dynamical signatures? (no) what was pressure generated? what is Equation of State of strongly-interacting matter? Must go beyond chemistry:  study dynamics of system well into deconfined phase (RHIC) lattice QCD applies

STAR 7 Warsaw STAR/ALICE HBT Workshop - May malisa uRQMD simulation of  s=200 GeV pure hadronic & string description (cascade) generally OK at lower energies applicability in very high density (RHIC) situations unclear produces too little collective flow at RHIC freeze-out given by last hard scattering

STAR 8 Warsaw STAR/ALICE HBT Workshop - May malisa The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) Colliding Au beams: 65 GeV + 65 GeV (  s=130 GeV)

STAR 9 Warsaw STAR/ALICE HBT Workshop - May malisa Geometry of STAR ZCal Barrel EM Calorimeter Endcap Calorimeter Magnet Coils TPC Endcap & MWPC ZCal FTPCs Vertex Position Detectors Central Trigger Barrel or TOF Time Projection Chamber Silicon Vertex Tracker RICH

STAR 10 Warsaw STAR/ALICE HBT Workshop - May malisa STAR Time Projection Chamber (TPC) Active volume: Cylinder r=2 m, l=4 m –139,000 electronics channels sampling drift in 512 time buckets –active volume divided into 70M 3D pixels On-board FEE Card: Amplifies, samples, digitizes 32 channels

STAR 11 Warsaw STAR/ALICE HBT Workshop - May malisa Peripheral Au+Au Collision at 130 AGeV Data Taken June 25, Pictures from Level 3 online display.

STAR 12 Warsaw STAR/ALICE HBT Workshop - May malisa Au on Au Event at CM Energy ~ 130 AGeV Data Taken June 25, 2000.

STAR 13 Warsaw STAR/ALICE HBT Workshop - May malisa Particle ID in STAR pions kaons protons deuterons electrons STAR dE/dx dE/dx PID range:  (dE/dx) =.08] p  ~ 0.7 GeV/c for K /   ~ 1.0 GeV/c for  p/p RICH PID range: GeV/c for K /  GeV/c for  p/p RICH “kinks”: K     + VoVo Decay vertices K s   + +  -   p +  -   p +  +  -   +  -   +  +  +    + K - Topology Combinatorics K s   + +  -   K + + K -   p +  -   p +  +    + +  -   p +  -   from K + K - pairs K + K - pairs m inv same event dist. mixed event dist. background subtracted dn/dm

STAR 14 Warsaw STAR/ALICE HBT Workshop - May malisa Kaon Spectra at Mid-rapidity vs Centrality Exponential fits to m T spectra: K+K+ K-K- (K + +K - )/2 KsKs STAR preliminary 0-6% 11-18% 26-34% 45-58% 58-85% Centrality cuts 0-6% 11-18% 26-34% 45-58% 58-85% Centrality cuts 0-6% 11-18% 26-34% 45-58% 58-85% Centrality cuts Good agreement between different PID methods

STAR 15 Warsaw STAR/ALICE HBT Workshop - May malisa Statistical Thermal Model: Fit Results T ~170 MeV (sim SPS): saturation?  b ~ 45 MeV (lower than SPS)

STAR 16 Warsaw STAR/ALICE HBT Workshop - May malisa First RHIC spectra - an explosive source data: STAR, PHENIX, QM01 model: P. Kolb, U. Heinz various experiments agree well different spectral shapes for particles of differing mass  strong collective radial flow mTmT 1/m T dN/dm T light heavy T purely thermal source explosive source T,  mTmT 1/m T dN/dm T light heavy very good agreement with hydrodynamic prediction

STAR 17 Warsaw STAR/ALICE HBT Workshop - May malisa Hydrodynamics: modeling high-density scenarios Assumes local thermal equilibrium (zero mean-free-path limit) and solves equations of motion for fluid elements (not particles) Equations given by continuity, conservation laws, and Equation of State (EOS) EOS relates quantities like pressure, temperature, chemical potential, volume –direct access to underlying physics Works qualitatively at lower energy but always overpredicts collective effects - infinite scattering limit not valid there –RHIC is first time hydro works! lattice QCD input

STAR 18 Warsaw STAR/ALICE HBT Workshop - May malisa Thermal motion superimposed on radial flow Hydro-inspired “blast-wave” thermal freeze-out fits to , K, p,   R  s E.Schnedermann et al, PRC48 (1993) 2462 T th = 107 MeV  = 0.55 preliminary M. Kaneta

STAR 19 Warsaw STAR/ALICE HBT Workshop - May malisa Momentum-space characteristics of freeze-out appear well understood Coordinate-space ? Probe with two-particle intensity interferometry (“HBT”) The other half of the story…

STAR 20 Warsaw STAR/ALICE HBT Workshop - May malisa “HBT 101” - probing source geometry Measurable! F.T. of pion source 5 fm 1 m  source  (x) r1r1 r2r2 x1x1 x2x2 p1p1 p2p2 1-particle probability  (x,p) = U * U 2-particle probability

STAR 21 Warsaw STAR/ALICE HBT Workshop - May malisa “HBT 101” - probing the timescale of emission KK R out R side Decompose q into components: q Long : in beam direction q Out : in direction of transverse momentum q Side :  q Long & q Out (beam is into board) beware this “helpful” mnemonic!

STAR 22 Warsaw STAR/ALICE HBT Workshop - May malisa Large lifetime - a favorite signal of “new” physics at RHIC hadronization time (burning log) will increase emission timescale (“lifetime”) magnitude of predicted effect depends strongly on nature of transition measurements at lower energies (SPS, AGS) observe  <~3 fm/c “”“” with transition cc Rischke & Gyulassy NPA 608, 479 (1996) 3D 1-fluid Hydrodynamics  ~ …but lifetime determination is complicated by other factors…

STAR 23 Warsaw STAR/ALICE HBT Workshop - May malisa First HBT data at RHIC STAR Collab., PRL (2001) Data well-fit by Gaussian parametrization Coulomb-corrected (5 fm full Coulomb-wave) “raw” correlation function projection 1D projections of 3D correlation function integrated over 35 MeV/cin unplotted components

STAR 24 Warsaw STAR/ALICE HBT Workshop - May malisa HBT excitation function STAR Collab., PRL (2001) decreasing parameter partially due to resonances saturation in radii geometric or dynamic (thermal/flow) saturation the “action” is ~ 10 GeV (!) no jump in effective lifetime NO predicted Ro/Rs increase (theorists: data must be wrong) Lower energy running needed!? midrapidity, low p T  - from central AuAu/PbPb

STAR 25 Warsaw STAR/ALICE HBT Workshop - May malisa Hydro attempts to reproduce data R out R side R long : model waits too long before emitting K T dependence approximately reproduced  correct amount of collective radial flow Right dynamic effect / wrong space-time evolution???  the “RHIC HBT Puzzle” generic hydro model emission timescale too long

STAR 26 Warsaw STAR/ALICE HBT Workshop - May malisa hydro evolution later hadronic stage? Failure to reproduce HBT a generic problem (Almost) no dynamical model correctly predicts HBT measurements The more realistic/“reasonable” a model is, the worse it seems to do… data

STAR 27 Warsaw STAR/ALICE HBT Workshop - May malisa Now what? “Realistic” dynamical models cannot adequately describe freeze-out distribution Seriously threatens hope of understanding pre-freeze-out dynamics Raises several doubts –is the data consistent with itself ? (can any scenario describe it?) –analysis tools understood? Attempt to use data itself to parameterize freeze-out distribution Identify dominant characteristics Examine interplay between observables (e.g. flow and HBT) Isolate features generating discrepancy with “real” physics models focus especially on timescales Attack problem from as many sides as possible

STAR 28 Warsaw STAR/ALICE HBT Workshop - May malisa Blastwave parameterization: Implications for HBT: radii vs p T Assuming , T obtained from spectra fits  strong x-p correlations, affecting R O, R S differently p T =0.2 p T =0.4 K K RSRS RORO “whole source” not viewed

STAR 29 Warsaw STAR/ALICE HBT Workshop - May malisa Blastwave: radii vs p T STAR data blastwave: R=13.5 fm,  freezeout =1.5 fm/c Using flow and temperature from spectra, can account for observed drop in HBT radii via x-p correlations, and R o <R s …but emission duration must be small Four parameters affect HBT radii p T =0.4 p T =0.2 K K

STAR 30 Warsaw STAR/ALICE HBT Workshop - May malisa Joint view of  freezeout: HBT & spectra spectra (  ) HBT common model/parameterset describes different aspects of f(x,p) Increasing T has similar effect on a spectrum as increasing  But it has opposite effect on R(p T )  opposite parameter correlations in the two analyses  tighter constraint on parameters caviat: not exactly same model used for this plot (different flow profiles) STAR preliminary

STAR 31 Warsaw STAR/ALICE HBT Workshop - May malisa From R long : Evolution timescale  t kinetic  Simple Sinyukov formula (S. Johnson) –R L 2 =  t kinetic  2 T/m T  t kinetic  = 10 fm/c (T=110 MeV) B. Tomasik (~3D blast wave) –  t kinetic  = 8-9 fm/c

STAR 32 Warsaw STAR/ALICE HBT Workshop - May malisa Kaon – pion correlations: dominated by Coulomb interaction Smaller source  stronger (anti)correlation K-p correlation well-described by: Blast wave with same parameters as spectra, HBT But with non-identical particles, we can access more information… Systematic program on non-identical particle correlations spearheaded by Warsaw group STAR preliminary Adam Kiesel, Fabrice Retiere

STAR 33 Warsaw STAR/ALICE HBT Workshop - May malisa Initial idea: probing emission-time ordering Catching up: cos  0 long interaction time strong correlation Ratio of both scenarios allow quantitative study of the emission asymmetry Moving away: cos  0 short interaction time weak correlation Crucial point: kaon begins farther in “out” direction (in this case due to time-ordering) purple K emitted first green  is faster purple K emitted first green  is slower

STAR 34 Warsaw STAR/ALICE HBT Workshop - May malisa measured K-  correlations - natural consequence of space-momentum correlations clear space-time asymmetry observed C+/C- ratio described by: –“standard” blastwave w/ no time shift Direct proof of radial flow-induced space-momentum correlations Kaon = 0.42 GeV/c Pion = 0.12 GeV/c STAR preliminary

STAR 35 Warsaw STAR/ALICE HBT Workshop - May malisa Balance functions: How they work For each charge +Q, there is one extra balancing charge –Q. Charges: electric, strangeness, baryon number Bass, Danielewicz, Pratt (2000)

STAR 36 Warsaw STAR/ALICE HBT Workshop - May malisa Balance functions - clocking the evolution Model predictions l Wide  early creation of charges l nn, e + e - collisions l Narrow  late hadronization / (Q)GP l central RHIC? Pythi a (wide ) Bjorken (narrow) Bass, Danielewicz, Pratt (2000)

STAR 37 Warsaw STAR/ALICE HBT Workshop - May malisa Balance Functions in STAR STAR Preliminary  Pairs Peripheral collisions approach Hijing (NN) Clear narrowing for central collisions In Bass/Danielewicz/Pratt model, central data consistent with: T chem ~ 175 MeVT kinetic ~ 110 MeV  t chem  = 10 fm/c  t kinetic  = 13 fm/c

STAR 38 Warsaw STAR/ALICE HBT Workshop - May malisa higher pressure gradient in-plane  “elliptical flow” more particles emitted in-plane x-space  p-space anisotropy Noncentral collision dynamics Equal energy density lines

STAR 39 Warsaw STAR/ALICE HBT Workshop - May malisa higher pressure gradient in-plane  “elliptical flow” more particles emitted in-plane x-space  p-space anisotropy experimentally quantified by v 2 Noncentral collision dynamics

STAR 40 Warsaw STAR/ALICE HBT Workshop - May malisa higher pressure gradient in-plane  “elliptical flow” more particles emitted in-plane x-space  p-space anisotropy experimentally quantified by v 2 hydro reproduces v 2 (p T,m) RHIC for p T < ~1.5 GeV/c system response  EoS early thermalization indicated Noncentral collision dynamics

STAR 41 Warsaw STAR/ALICE HBT Workshop - May malisa higher pressure gradient in-plane  “elliptical flow” more particles emitted in-plane x-space  p-space anisotropy experimentally quantified by v 2 hydro reproduces v 2 (p T,m) RHIC for p T < ~1.5 GeV/c system response  EoS early thermalization indicated Noncentral collision dynamics STAR preliminary see talk of J. Fu v2v2 p T (GeV/c) flow of neutral strange particles PID beyond p T =1 GeV/c

STAR 42 Warsaw STAR/ALICE HBT Workshop - May malisa higher pressure gradient in-plane  “elliptical flow” more particles emitted in-plane x-space  p-space anisotropy experimentally quantified by v 2 hydro reproduces v 2 (p T,m) RHIC for p T < ~1.5 GeV/c system response  EoS early thermalization indicated Again, hydro reproduces p-space freezeout shape  evolution duration? Noncentral collision dynamics STAR preliminary see talk of J. Fu v2v2 p T (GeV/c)

STAR 43 Warsaw STAR/ALICE HBT Workshop - May malisa Blast-wave fit to low-p T v 2 (p T,m) STAR, PRL (2001) spatial anisotropy indicated consistent with out-of-plane extended source (but ambiguity exists)  p =0°  p =90° R side (large) R side (small) possible to “see” via HBT relative to reaction plane? expect large R side at 0  small R side at 90  2 nd -order oscillation

STAR 44 Warsaw STAR/ALICE HBT Workshop - May malisa Out-of-plane extended source ~ short system evolution time STAR preliminary Same blastwave parameters as required to describe v 2 (p T,m), plus two more: –R y = 10 fm  = 2 fm/c Both p-space and x-space anisotropies contribute to R(  ) –mostly x-space: definitely out-of-plane calibrating with hydro,  freezeout ~ 7 fm/c R os 2 - new “radius” important for azimuthally asymmetric sources

STAR 45 Warsaw STAR/ALICE HBT Workshop - May malisa RHIC 130 GeV Au+Au Disclaimer: all numbers (especially time) are approximate Low-p T dynamics — one (naïve?) interpretation: rapid evolution and a “flash” K-  K * yield

STAR 46 Warsaw STAR/ALICE HBT Workshop - May malisa Physics at “high” p T (~6 GeV/c) hadrons q q leading particle leading particle Jets modified in heavy ion collisions -Parton Energy loss in dense nuclear medium -Modification of fragmentation function

STAR 47 Warsaw STAR/ALICE HBT Workshop - May malisa Jets in STAR? OPAL qq jet event STAR Au+Au event It’s a little complicated… Need another way to get at hard scattering physics.

STAR 48 Warsaw STAR/ALICE HBT Workshop - May malisa Physics at “high” p T (~6 GeV/c) hadrons q q leading particle suppressed leading particle suppressed hadrons q q leading particle leading particle Jets modified in heavy ion collisions -Parton Energy loss in dense nuclear medium -Modification of fragmentation function 1) high-pT suppression relative to NN (especially in central collisions) 2) finite, non-hydro v 2 due to energy loss (non-central collisions) see talk of J. Klay y Jet 1 Jet 2 x

STAR 49 Warsaw STAR/ALICE HBT Workshop - May malisa Inclusive spectra preliminary Statistical errors only power-law fits

STAR 50 Warsaw STAR/ALICE HBT Workshop - May malisa Power law fits Power Law: “pQCD inspired” Fits wide range of hadronic spectra: ISR  Tevatron Good fits at all centralities (  2 /ndf~1) Smooth dependence on centrality most peripheral converges to Nucleon- Nucleon reference (UA1) STAR preliminary centrality

STAR 51 Warsaw STAR/ALICE HBT Workshop - May malisa Central collisions: suppression of factor 3 (confirms PHENIX) Peripheral collisions: “enhancement” consistent with zero (uncertainties due to and NN reference) Smooth transition central  peripheral preliminary low p T scales as

STAR 52 Warsaw STAR/ALICE HBT Workshop - May malisa Azimuthal anisotropy - theory and data Preliminary p T <2 GeV: good description by hydrodynamics p T >4 GeV: hydro fails but finite v 2 finite energy loss  finite v 2 at high p T sensitive to gluon density y Jet 1 Jet 2 x model: Gyulassy, Vitev and Wang, (2001) Low p T : parameterized hydro High p T : pQCD with GLV radiative energy loss

STAR 53 Warsaw STAR/ALICE HBT Workshop - May malisa V2 centrality dependence Preliminary all centralities: finite v 2 at high p T

STAR 54 Warsaw STAR/ALICE HBT Workshop - May malisa But are we looking at jets? - 2 Particle Correlations Trigger particle p T >4 GeV/c, |  azimuthal correlations for p T >2 GeV/c short range  correlation: jets + elliptic flow long range  correlation: elliptic flow  subtract correlation at |      NB: also eliminates the away-side jet correlations extracted v 2 consistent with reaction-plane method what remains has jet-like structure  first indication of jets at RHIC! preliminary 0-11%

STAR 55 Warsaw STAR/ALICE HBT Workshop - May malisa STAR vs UA1 UA1: Phys. Lett. 118B, 173 (1982) (most events from high E T trigger data) UA1: very similar analysis (trigger p T >4 GeV/c) But sqrt(s)=540 GeV, |  |<3.0 preliminary

STAR 56 Warsaw STAR/ALICE HBT Workshop - May malisa Brief Summary - (just a small set of STAR results) chemistry: wide range of particle yields well-described by thermal model T chem ~ 170 MeV  b ~ 45 MeV p T dependence of yields (e.g. baryon dominance) consistent with radial flow dynamics at p T < 2 GeV/c “real” model (hydro) reproduces flow systematics, but not HBT finger-physics analysis of probes sensitive to time: short system evolution, then emission in a flash T chem ~ 170 MeVT kin ~ 110 MeV t chem ~ 10 fm/ct kin ~ 13 fm/c naïve? unphysical? useful feedback to modelers? dynamics at p T > 2 GeV/c hydro picture breaks down preliminary jet signal observed evidence for medium effects at high p T

STAR 57 Warsaw STAR/ALICE HBT Workshop - May malisa THE END

STAR 58 Warsaw STAR/ALICE HBT Workshop - May malisa Resonance survival rate time chemical freeze out T~170 MeV thermal freeze out T~110MeV d1 R d2 d1 R d2 UrQMD: signal loss in invariant mass reconstruction K*(892)  (1520)  SPS (17 GeV) [1] 66% 50% 26% RHIC (200GeV) [2] 55% 30% 23% short-lived resonances –K*(892)  = 3.9 fm/c –  (1520)  = 12.8 fm/c Rescattering of daughters between chemical and kinetic freeze-out washes out the resonance signal –Sensitive to  t kinetic  -  t chemical  kinetic rescattering

STAR 59 Warsaw STAR/ALICE HBT Workshop - May malisa Resonance reconstruction (via combinatorics): K* and  (1520) from STAR K *0  K + +  - K *0  K - +  + multiplicity for |y| <0.5  K* 0  |y|<0.5 = 10.0  0.8  25% Upper limit estimation: dN/dy preliminary  (1520)  |y|<1 < 1.2 at 95% C. L.  (1520)  p + K - m inv (GeV/c 2 )

STAR 60 Warsaw STAR/ALICE HBT Workshop - May malisa Resonance survival rate: Rafelski’s picture Upper limit Combining both K* and  (1520): Caveats: –partial  “quenching” (width broadening) allows for higher T, still small  –T chem ~100 MeV ?!? Thermal fit: T ~ 170 MeV –no evidence of low-p T suppression –Possible K* regeneration? –  t kinetic  -  t chemical  ~ 0-3 fm/c

STAR 61 Warsaw STAR/ALICE HBT Workshop - May malisa p T spectra: Flavor Dependence Enhancement at ~2 GeV is not specific to baryons  mass effect  simplest explanation: radial flow)

STAR 62 Warsaw STAR/ALICE HBT Workshop - May malisa A consistent picture within blastwave

STAR 63 Warsaw STAR/ALICE HBT Workshop - May malisa Something different vs p T ? Particle/Antiparticle Ratios STAR Preliminary Within the errors no or very small p T dependence (as one might expect from simply flow) see talk by B. Norman

STAR 64 Warsaw STAR/ALICE HBT Workshop - May malisa Azimuthal variation of transverse flow and source deformation Consistent values for source deformation from HBT and elliptic flow

STAR 65 Warsaw STAR/ALICE HBT Workshop - May malisa Excitation function of spectral parameters Kinetic “temperature” saturates ~ 140 MeV already at AGS Explosive radial flow significantly stronger than at lower energy System responds more “stiffly”? Expect dominant space-momentum correlations from flow field

STAR 66 Warsaw STAR/ALICE HBT Workshop - May malisa Ratios driving the thermal fits Plots from D. Magestro, SQM2001

STAR 67 Warsaw STAR/ALICE HBT Workshop - May malisa Blast Wave Mach I - central collisions  R  s Ref. : E.Schnedermann et al, PRC48 (1993) 2462 flow profile selected (  t = s (r/R max ) n ) mtmt 1/m t dN/dm t T fo A tt 2-parameter (T fo,  t ) fit to m T distributions

STAR 68 Warsaw STAR/ALICE HBT Workshop - May malisa Blastwave Mach II - Including asymmetries R tt –Flow Space-momentum correlations = 0.6 (average flow rapidity) Assymetry (periph) :  a = 0.05 –Temperature T = 110 MeV –System geometry R = 13 fm (central events) Assymetry (periph event) s 2 = 0.05 –Time: emission duration  = emission duration analytic description of freezeout distribution: exploding thermal source

STAR 69 Warsaw STAR/ALICE HBT Workshop - May malisa Comparison to Hijing Ratio of integrals over correlation peak: 1.3 Hijing fragmentation is independent of quenching

STAR 70 Warsaw STAR/ALICE HBT Workshop - May malisa High-p T highlights Qualitative change at 2 GeV Jet-like structure

STAR 71 Warsaw STAR/ALICE HBT Workshop - May malisa measured K-  correlations - natural consequence of space-momentum correlations clear space-time asymmetry observed C+/C- ratio described by: –static (no-flow) source w/  t K  -  t   =4 fm/c –“standard” blastwave w/ no time shift We “know” there is radial flow  further evidence of very rapid freezeout Direct proof of radial flow-induced space-momentum correlations Kaon = 0.42 GeV/c Pion = 0.12 GeV/c STAR preliminary

STAR 72 Warsaw STAR/ALICE HBT Workshop - May malisa Vector meson production in Ultra-peripheral collisions Signal region: p T <0.15 GeV  0 P T 00 Au  qq b > 2R  electromagnetic interactions d  /dp T consistent with predictions for coherent  0 production

STAR 73 Warsaw STAR/ALICE HBT Workshop - May malisa Models to Evaluate T ch and  B Assume: Hadron resonance ideal gas Comparable particle ratios to experimental data Q i : 1 for u and d, -1 for  u and  d s i : 1 for s, -1 for  s g i : spin-isospin freedom m i : particle mass T ch : Chemical freeze-out temperature  q : light-quark chemical potential  s : strangeness chemical potential  s : strangeness saturation factor Particle density of each particle: J.Rafelski PLB(1991)333 J.Sollfrank et al. PRC59(1999)1637 Statistical Thermal Model F. Becattini P. Braun-Munzinger et al. PLB(1999) Assume: thermally and chemically equilibrated fireball at hadro-chemical freeze-out law of mass action is applicable !!! Recipe: grand canonical ensemble to describe partition function  density of particles of species  i fixed by constraints: Volume V,, strangeness chemical potential  S, isospin input: measured particle ratios output: temperature T and baryo- chemical potential  B Chemical Freeze-Out Model

STAR 74 Warsaw STAR/ALICE HBT Workshop - May malisa  B/B Ratios at RHIC Ratios calculated for central events at mid- rapidity, averaged over experimental acceptance in p t. With the assumption of equal acceptance of particle and antiparticle no corrections have to be applied Except: Absorption in material Production of secondaries in material  B/B ratios experimentally robust 0.94  STAR preliminary