Event anisotropy at RHIC

Transcription

1 Event anisotropy at RHIC Nu Xu - LBNL 1) Introduction 2) Experimental details and 200 GeV results v 2 (m 0, p T, y, b, A) 3) Summary and outlook PHENIX: N. Ajitanand, S. Esumi, R. Lacey, J. Rak PHOBOS: S. Manly STAR: K. Filimonov, J. Fu, H. Huang, A. Poskanzer, H. Ritter, R. Snellings P. Sorensen, A. Tang, S. Voloshin, E. Yamamoto, H. Zhang 1

2 Introduction Theory: J. Ollitrault, H. Sorge Exp: A. Poskanzer, S. Voloshin?????? Initial Condition - baryon transfer - E T production - parton dof System Evolves - parton/hadron expansion Bulk Freeze-out - hadron dof - interactions stop Q 2 time J/y, D W f X L, K* p, K D, p d, HBT v 2 saturates b T saturates 2

3 Transverse flow observables t dn p dp dydj t = 1 2p t dn p dp dy t Ø Œ1+ º i=1 2v cos(i( j i -? R ø )) œ ß As a function of particle mass: Directed flow (v 1 ) early Elliptic flow (v 2 ) early Radial flow integrated over whole evolution Note: 1) Effect of collectivity is accumulative sum of all processes as long as interactions are there. 2) No thermalization is needed pressure gradient depends on density gradient and interactions. 3

4 Anisotropy parameter v 2 coordinate-space-anisotropy momentum-space-anisotropy y p y x p x Initial/final conditions, dof, EOS e 2 2 Æ - x æ = v2 = cos2j, j 2 2 Æ y + x æ y -1 = tan ( p p y x ) 4

5 PHENIX: Reaction Plane Measurement Beam-Beam Counter η = 3 ~ 4 64 pmts / each charged particles S. Esumi QM02 dn ch /dη η beam line - Reaction plane measured at 3 units of rapidity away from the collision point. - Less non-flow contribution. Central Arms η < 0.35 Dch,PCs,TOF,EMCAL momentum, PID collision point Pair analysis uses charged tracks at mid-rapidity. 5

6 PHENIX: reaction plane and resolution h = -3.5 vs h = +3.5 (directed : n=1) h = -3.5 vs h = +3.5 (elliptic : n=2) h =3.5 vs h < 0.35 (elliptic : n=2) F 1 (h = -3.5) F 2 (h = -3.5) F 2 ( h = 3.5) S. Esumi DF = F 1 A - F 2 B F 1 (h = +3.5) F 2 (h = +3.5) F 2 ( h < 0.35) Reaction plane resolution: ~ 0.4 <cos(df)> A: (h = -3.5) B: (h = +3.5) <cos(2 DF)> A: (h = -3.5) B: (h = +3.5) <cos(2 DF)> A: ( h = 3.5) B: ( h < 0.35) charged multiplicity 6

7 PHENIX: v 2 vs. centrality Charge particle v 2 r.p. η = -4~-3 r.p. η = 3~4 r.p. η = 3~4 PHENIX Preliminary --- statistical error --- +systematic error Au+Au at 200GeV 1) v 2 ( η <0.35) with 3 different reaction planes at ( η =3~4) 2) charged particles 0.2 < p T < 10 GeV/c Centrality (%) <sin(2(φ Φ))> S. Esumi 7

8 PHENIX: v 2 vs. p T Charge particle v 2 reaction plane based (r.p. η =3~4) pair wise correlation analysis PHENIX Preliminary Au+Au at 200GeV (M.B.) 1) charged particles v 2 within ( η <0.35) 2) Error: a) statistic only b) a) resolution syst. c) b) b.g. syst. Transverse momentum p T (GeV/c) S. Esumi, N. Ajitanand Quark Matter Conference 02 8

9 PHENIX: v 2 from pair analysis Au + Au at 200 GeV N. N. Ajitanand (QM02) Minimum Bias Minimumbias < Centrality < 40 (%) 10 < Centrality < < Centrality < v v PHENIX PRELIMINARY pt (GeV/c) 0.05 PHENIX PRELIMINARY pt (GeV/c) v 2 seems to saturate at ~ 2.5 GeV/c; In the most central bin, indication of decrease (?) Nu Xu INT Workshop, December 2002

10 PHENIX: v 2 of identified hadrons PHENIX Preliminary Au+Au at 200 GeV (r.p. η =3~4) Anisotropy v 2 Negatives (π -,K - ), p Positives (p +,K + ), p Transverse momentum p T (GeV/c) 1) Below p T ~ 2 GeV/c, hydro results fit data and v 2 (p) < v 2 (π,k). 2) The hydro calculations include the1 st order phase transition with T fo =120MeV. 2) Above, p T ~ 2 GeV/c, v 2 seem to saturate and v 2 (p) > v 2 (π,k) (?) S. Esumi, QM02 Model: P.Huovinen, et al., Phys. Lett. B503, 58 (2001) 10 10

11 PHOBOS: Analysis methods Hit-based analysis Track-based analysis Large h coverage Event-by-event Uniform acceptance in f Separated sub-events p t dependence Less background sensitive Minimal MC dependence (Species dependence) 11 11

12 PHOBOS: v 2 vs. centrality v 2 v (hit) v (track) h <1 hit track PHOBOS Preliminary 200 GeV Au-Au Hit and track-based results agree! <N part > S. Manly, QM

13 PHOBOS: v 2 vs. p T 0<h<1.5 v 2 PHOBOS preliminary h + + h GeV Au-Au track-weighted centrality averaging (top 55%) 17% scale error v 2 appears to saturate for p T >2 GeV/c S. Manly, QM

14 PHOBOS: v 2 vs. h and energy Charged particle v 2 Au + Au collisions 200 GeV 130 GeV Pseudo-rapidity η No-boost invariant at RHIC - VERY IMPORTANT! PHOBOS: 200 GeV 130 GeV 1) Hit-based result v 2 (200) & v 2 (130) are similar. 2) Dramatic variation in pseudo-rapidity. 3) <N part > ~ GeV result: nucl-ex/ , submitted to PRL 14 14

15 STAR event plane resolution (p t weighting random subevents) Au + Au at 130 GeV Au + Au at 200 GeV Paul Sorensen Collision Centrality Maximum Λ: 0.58 K S : 0.68 at 130 GeV resolutions: Λ: 0.80 K S : 0.80 at 200 GeV 15 15

16 STAR: v 2 vs. p T and centrality Charged particle v 2 Au + Au at 200 GeV, STAR Preliminary STAR Preliminary Transverse momentum p T (GeV/c) K. Filimonov, QM02 1) Finite v 2 up to 12 GeV/c in mid-peripheral bin 2) Saturate at p T > 2.5 GeV/c for all centrality bins, except 3) for the most central bin (?) K. Filimonov, QM

17 Non-flow correlations 1) There are non-reaction plane related correlations! ~ 20% and could be p T dependent! 2) Model comparisons should be careful! STAR Preliminary A. Tang 17 17

18 STAR: : Particle identification 1) de/dx in TPC (p T < 1 GeV/c) : π,k,p 2) RICH (0.5 < p T < 3 GeV/c) : (π,k),p 3) V 0 -Topology reconstruction K 0,Λ,Ξ.. 4) Mixed events method: K*, φ K p TPC π π K p RICH 18 18

19 STAR: PID v 2 vs. p T Particle v 2 K. Filimonov, QM02 Model: P.Huovinen, et al., Phys. Lett. B503, 58 (2001) STAR Preliminary Transverse momentum p T (GeV/c) Transverse momentum p T (GeV/c) As in 130 GeV collision, the mass dependence of v 2 at low p T (<1 GeV/c) is well described by hydro calculations early thermalization at RHIC (?) 19 19

20 STAR v 2 : of p,, K and p Au+Au at 200 GeV 1) Below p T ~ 2 GeV/c, hydro results fit data and v 2 (p) < v 2 (K) < v 2 (π) STAR Preliminary 2) The hydro calculations include the1st order phase transition with T fo =120MeV. 2) Above, p T ~ 2 GeV/c, v 2 seem to saturate and v 2 (p) > v 2 (π,k) (?) K. Filimonov, QM02 Model: P.Huovinen, et al., Phys. Lett. B503, 58 (2001) 20 20

21 STAR: : Strange hadron (K 0, L ) v 2 1) High quality M.B. data!!! 2) At p t < 2 GeV/c, hydro behavior, v 2 (Λ) < v 2 (K) 3) At p t > 2.5 GeV/c, v 2 (Λ) > v 2 (K)! - CGC? - Coalescence? - Energy loss? Partonic dof relevant! Model P.Huovinen, et al., Phys. Lett. B503, 58 (2001) Paul Sorensen, Jinghua Fu 21 21

22 PHENIX & STAR meson vs. baryon v 2 1) High quality M.B. data!!! 2) Consistent between PHENIX and STAR p T < 2 GeV/c v 2 (light) > v 2 (heavy) p T > 2.5 GeV/c v 2 (light) < v 2 (heavy) Model: P.Huovinen, et al., Phys. Lett. B503, 58 (2001) 22 22

23 STAR: : Strange hadron (K 0, L ) v 2 Centrality dependence: 1) Saturation is not clear; 2) In peripheral events: v 2 (Λ) > v 2 (K) at p T > 2 GeV/c but less clear in more central events! Surface emission? STAR Preliminary: See Sorensen s talk 23 23

24 Summary and outlook 1) Charged particle: i) M.B. events, saturated at ~ 15-17%, for p T > 2.5, to 12 GeV/c; ii) Dramatic change in pseudo-rapidity; iii) Non-flow correlations are important, at high p T region 2) Identified particle: i) p T < 2 GeV/c, M.B. events, hydro calculations fit v 2 (π) > v 2 (K) > v 2 (p) > v 2 (Λ) [ v 2 (heavy) < v 2 (light) ] ii) p T > 2 GeV/c, for all centrality bins, v 2 (π, K) < v 2 (p, Λ) [ v 2 (heavy) > v 2 (light) ] 3) Future: i) Understand azimuthal correlations in p+p collisions ii) π,k,p,λ v 2 up to p T ~ 5 GeV/c test partonic contributions iii) Multi-strange particle v 2 test partonic flow(?) 24 24

25 Partonic Flow at RHIC(?)? YES NO 1) Non-zero values of v 2 for Ω,... 2) Increase of T (<p T >) for Ω, D, J/ψ 25 25