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Elliptic Flow Outline: Methods: - the use of many-particle correlations in many different approaches - non-flow and flow fluctuations Tr ans ve r s e Plane ε Y y x y 2 x 2 2 2 X Data: - centrality dependence at different energies - v2(pt) at different energies - v2(pt) of identified particles and fits to the blast wave model - v2(pt) at high pt. - azimuthal correlations at high pt’s. Models: - 2d and 3d hydro, hydro+RQMD - parton cascade model(s) (MPC, AMPT) - Color Glass Condensate (A. Krasnitz et al.) - Hadronic rescatterings ( T. Humanic) -… Speculations: - Constituent quark model - v2/ vs (dN/dy) /S v2 px 2 py 2 px py 2 2 cos( 2φ ) SPS. Centrality dependence. Preliminary STAR Preliminary v2 = 0.04 Elab=40GeV 158 GeV NA45, QM’01 - Monotonically increases with the beam energy - Steeper centrality dependence at 158 GeV compared to 40 GeV ? Centrality dependence. RHIC. Note possible dependence on low pt cut 200 GeV: 0.2< pt < 2.0 130 GeV: 0.075< pt < 2.0 200 GeV: 0.150< pt < 2.0 4-part cumulants STAR v2=0.05 STAR Preliminary 200 GeV: Preliminary - Consistent results - At 200 GeV better pronounced decrease of v2 for the most peripheral collisions. Preliminary v2 vs pseudorapidity; 3d hydro. 3d hydrodynamical calculations (boost invariant initial conditions) do not reproduce v2(); can the agreement be reached by modifying the initial conditions? v2(pt), non-flow vs pt STAR Preliminary Non-flow contribution (on average) : - about 7-10% at SPS, 160 GeV. - about 15% @ 130 GeV - about 20% @ 200 GeV - could slightly increase with transverse momentum Constituent quark model + coalescence coalescence fragmentation Low pt quarks High pt quarks v2(pbar) v2(p,K) Coalescence in the intermediate region (rare products): v2 baryons d nM d nq p p / 2 q M d 3 pM d 3 pq 3 mesons quarks 3 2 Preliminary v2(proton) v2(p,K) pt Side-notes: a) more particles produced via coalescence vs parton fragmentation larger mean pt… b) higher baryon/meson ratio - What is the centrality dependence of the effect? Jets at RHIC Find this……….in this p+p jet+jet (STAR@RHIC) jet parton nucleon nucleon Au+Au ??? (STAR@RHIC) Jets and two-particle azimuthal distributions p+p dijet • trigger: highest pT track, pT>4 GeV/c • Df distribution: 2 GeV/c<pT<pTtrigger • normalize to number of triggers Phys Rev Lett 90, 082302 N.B. shifted horizontally by p/2 relative to previous STAR plots! trigger Partonic energy loss in dense matter Bjorken, Baier, Dokshitzer, Mueller, Pegne, Schiff, Gyulassy, Levai, Vitev, Zhakarov, Wang, Wang, Salgado, Wiedemann,… Multiple soft interactions: Gluon bremsstrahlung CR S 2 DE qˆL 4 kT2 medium qˆ S glue Opacity 2 E jet 3 expansion: DE pC ACa S dglue , r Log 2 L Strong dependence of energy loss on gluon density glue: measure DE color charge density at early hot, dense phase Leading hadron suppression Wang and Gyulassy: DE softening of fragmentation suppression of leading hadron yield Ivan Vitev, QM02 d 2 N AA / dpT d RAA ( pT ) TAAd 2 NN / dpT d - Au+Au and p+p: inclusive charged hadrons PhysRevLett 89, 202301 nucl-ex/0305015 p+p reference spectrum measured at RHIC Suppresion of inclusive hadron yield RAA Au+Au relative to p+p RCP Au+Au central/peripheral nucl-ex/0305015 • central Au+Au collisions: factor ~4-5 suppression • pT>5 GeV/c: suppression ~ independent of pT Azimuthal distributions in Au+Au Au+Au peripheral Au+Au central pedestal and flow subtracted Phys Rev Lett 90, 082302 Near-side: peripheral and central Au+Au similar to p+p Strong suppression of back-to-back correlations in central Au+Au ? Suppression of away-side jet consistent with strong absorption in bulk, emission dominantly from surface Is suppression an initial or final state effect? Initial state? strong modification of Au wavefunction (gluon saturation) Final state? partonic energy loss in dense medium generated in collision Inclusive suppression: theory vs. data RCP pQCD-I: Wang, nucl-th/0305010 pQCD-II: Vitev and Gyulassy, PRL 89, 252301 Saturation: KLM, Phys Lett B561, 93 nucl-ex/0305015 Final state Initial state pT>5 GeV/c: well described by KLM saturation model (up to 60% central) and pQCD+jet quenching Is suppression an initial or final state effect? Initial state? Final state? gluon saturation How to discriminate? Turn off final state d+Au collisions partonic energy loss d+Au vs. p+p: Theoretical expectations RAB Inclusive spectra If Au+Au suppression is final state 1.1-1.5 1 If Au+Au suppression is initial state (KLM saturation: 0.75) ~2-4 GeV/c High pT hadron pairs pT broadening? pQCD: no suppression, small broadening due to Cronin effect saturation models: suppression due to mono-jet contribution? 0 0 p/2 p Df (radians) All effects strongest in central d+Au collisions suppression? Inclusive yield relative to binaryscaled p+p RAB dN AB / dpT d TAB d pp / dpT d • d+Au : enhancement Au+Au: strong suppression • pT=4 GeV/c: cent/minbias = 1.110.03 central collisions enhanced wrt minbias Suppression of the inclusive yield in central Au+Au is a final-state effect Azimuthal distributions pedestal and flow subtracted Near-side: p+p, d+Au, Au+Au similar Back-to-back: Au+Au strongly suppressed relative to p+p and d+Au Suppression of the back-to-back correlation in central Au+Au is a final-state effect v2(pT) : saturates? going down? STAR Preliminary NA45 - saturation at SPS? - RHIC: weak indication of decreasing.. Have we found the Quark Gluon Plasma at RHIC? We now know that Au+Au collisions generate a medium that • is dense (pQCD theory: many times cold nuclear matter density) • is dissipative • exhibits strong collective behavior This represents significant progress in our understanding of strongly interacting matter We have yet to show that: • dissipation and collective behavior both occur at the partonic stage • the system is deconfined and thermalized • a transition occurs: can we turn the effects off ? Not yet, there is still work to do Things to Look Forward to This QM: First glance at resonances at RHIC: 0(770) p+ p- and f0(980) p+ p- |y| < 0.5 Au+Au 40% to 80% STAR Preliminary 0.2 pT 0.9 GeV/c 0 f0 K0S K*0 pp STAR Preliminary 0.2 pT 0.8 GeV/c Short-lived resonances: • provide information on the collision dynamics • rescattering regeneration 0 f0 K0S K*0 Single Electrons - Run I See talk R.Averbeck Single Electron Results conversion conversion p0 ee 0 ee, p0 ee 3p ee, p0ee ee, 3p0 f ee, ee ee, p0ee f ee, ee Quark Matter 2002 eeee ’ ee ee James Nagle for the PHENIX Collaboration J/y e+e- in Gold-Gold ! N=10.8 3.2 (stat) 3.8 (sys) N=10.8 3.2 (stat) 3.8 (sys) N=5.9 + 2.4 (stat) 0.7 (sys) N=5.9 + 2.4 (stat) 0.7 (sys) Seven different mass fitting and counting methods used to determine systematic error in the number of counts. Observations • Our electron data is consistent with binary scaling within our current statistical and systematic errors. • NA50 has inferred a factor of ~3 charm enhancement at lower energy. We do not see this large effect at RHIC. • PHENIX observes a factor of ~3-4 suppression in high pT p0 relative to binary scaling. We do not see this large effect in the single electrons from charm. Possibly less energy loss of charm quarks in medium due to “dead-cone” effect.1 NA50 - Eur. Phys. Jour. C14, 443 (2000). Binary Scaling PHENIX Preliminary N part 1Y.L.Dokshitzer and D.E. Kharzeev, hep-ph/0106202 Model Comparisons We different J/yJ/y patterns all normalized to to Weshow showthree three different patterns all normalized intersect ourour proton-proton datadata point. intersect proton-proton point. (1) thethe number of binary collisions (1)J/y J/yscale scalewith with number of binary collisions (2) normal nuclear absorption with with J-N=7.1 mb (2)J/y J/yfollow follow normal nuclear absorption J-N=7.1 1 (3) J/y follow same pattern as NA50 (J/y / DY(mb)) mb (3) J/y follow same pattern as NA50 (J/y / DY(mb))1 Warning This plot has been known to deceive theorists! 1NA50 Phys. Lett. B521, 195 (2001)