Masashi Kaneta, LBNL Masashi Kaneta for the STAR collaboration First results from STAR experiment at RHIC Lawrence Berkeley National Lab.

Masashi Kaneta, LBNL RHIC'S ULTIMATE GOAL: QUARK-GLUON PLASMA

Masashi Kaneta, LBNL Brookhaven National Lab.

Masashi Kaneta, LBNL The STAR collaboration ~ 400 collaborators 34 institutions 7 countries

Masashi Kaneta, LBNL STAR Institutions U.S. Labs: Argonne, Berkeley, and Brookhaven National Labs U.S. Universities: Arkansas, UC Berkeley, UC Davis, UCLA, Carnegie Mellon, Creighton, Indiana, Johns Hopkins, Kent State, MIT, MSU, CCNY, Ohio State, Penn State, Purdue, Rice, UT Austin, Washington, Wayne State, Yale Brazil : Universidade de Sao Paol 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

Masashi Kaneta, LBNL STAR Detector Year1 Ready for next run Next year(2002) or later ZDC Silicon Vertex Tracker Central Trigger Barrel FTPCs Barrel EMC (install over next 4 years) Vertex Position Detectors Endcap EMC (half in 2003) Magnet Coils TPC Endcap & MWPC ZDC RICH yr.1 SVT ladder + TOF patch Silicon Strip Detector Time Projection Chamber

Masashi Kaneta, LBNL Outer and Inner Sectors of the Pad Plane 60 cm 190 cm 24 sectors 12 on each side Large pads for good dE/dx resolution in the Outer sector Small pads for good two track resolution in the inner sector

Masashi Kaneta, LBNL Mating the OFC & Gas Vessel Winding Outer Field Cage Mating OFC & Gas Vessel OFC Check Moving the Central Membrane

Masashi Kaneta, LBNL The STAR TPC Under Construction at LBL First Successful Mating of: Gas Vessel Outer Field Cage Sector Wheels Central membrane

Masashi Kaneta, LBNL The TPC arrives at BNL from LBL on 11/6/97

Masashi Kaneta, LBNL System Tests 10/19/98-10/30/98 TPC outside the magnet All FEE electronics installed on TPC Slow Controls tested Cathode Anode Gating Grid CTB trigger prototype miniDAQ TPC integration tests on the assembly hall floor

Masashi Kaneta, LBNL Au+Au,  s NN =130 GeV Central Event From real-time Level 3 display. ~2000 tracks per event Data Taken June 25, 2000.

Masashi Kaneta, LBNL Particle identification by dE/dx  K p e |p/Z| [GeV/c] dE/dx [keV/cm]

Masashi Kaneta, LBNL Focus on Hadrons Measured : h ,  ±, K ±, K 0 s, K *0, K *0, p, p, d, 3 He, 3 He, t,     In future :  0, ,   +  ,   ’,     , J/  and more Freeze-out conditions of low momentum hadrons by: Spectra/Ratios Thermal/Chemical Freeze-out Particle correlations Size parameters Event anisotropy v 2

Masashi Kaneta, LBNL Spectra

Masashi Kaneta, LBNL Spectra Low p T spectra h , , K, p  Thermal freeze-out High p T spectra h    hard process Particle ratios, yield (dN/dy, dN/d  ) p/p, ,    , K  /K , K  /  , p/  , K *0 /h   Stopping  Chemical freeze-out d/p  Coalescence

Masashi Kaneta, LBNL h - multiplicity 6% systematic error shown on 3 points only Preliminary 5% Central ZDC pulse height CTB pulse height

Masashi Kaneta, LBNL h - centrality dependence 5% 10% 20% 30% 40%

Masashi Kaneta, LBNL h- centrality dependence (cont.) 15% Increase in from 80% sample to top 5% central NA49 UA1 STAR, Preliminary

Masashi Kaneta, LBNL h - p T distribution STAR Preliminary Statistical errors negligible Errors on points: systematic error on STAR data Gray bars: cumulative error including UA1 scaling Hard: Binary collisions T AA = 26 ± 2 mb -1 Soft: Wounded nucleon STAR Preliminary

Masashi Kaneta, LBNL Particle Identification dE/dx e, , K, p Kink, V 0, Mixed event Kaon to muon decay  , etc. Resonances K d e p  “kinks”: K     + VoVo

Masashi Kaneta, LBNL  Typical e + e  pair from  e+e+ e+e+ e+e+ e+e+ e-e- e-e- e-e- e-e-  invariant mass [GeV]  STAR Preliminary and 0 The e + e  pair from  conversion is measured Large  acceptance p T = 50 MeV/c to ~4 GeV/c, |  |<1.8

Masashi Kaneta, LBNL  K + K - 

Masashi Kaneta, LBNL Identified particle spectra Inverse slope: 565  40(sta.)  50(sys.) MeV Inverse slope: 190  15(sta.)  20(sys.) MeV -- K-K- p Inverse slope: 300  15(sta.)  30(sys.) MeV central collisions  6% 11-18% 26-34% 45-58% 58-85%

Masashi Kaneta, LBNL Inverse slope vs. centrality K - (kink) P e r i p h e r a l  C e n t r a l STAR Preliminary Indicate increased radial flow in central collisions at RHIC Event fraction [%]

Masashi Kaneta, LBNL Kink K  Kaon from muon decay  KK  Inverse slope: 267  5(sta.)  10(sys.) MeV Inverse slope: 272  5(sta.)  10(sys.) MeV K-K- K+K+ |y|<0.5 Event fraction = top 7% STAR Preliminary |y|<0.5 Event fraction = top 7%

Masashi Kaneta, LBNL “Kink” Kaon Rapidity Distribution Mid-y K + dN/dy = 35 ±3(stat.)±5(sys.) Mid-y K - dN/dy = 30±2.5(stat.)±4(sys.)

Masashi Kaneta, LBNL ( ) m T distribution from Hydrodynamical model Cylindrical source Flow profile included  R ss Ref. : E.Schnedermann et al, PRC48 (1993) 2462 Inverse slope parameter Ref.: T.Csörgő and B, Lörstad, PRC52 (1995) 3291 ~ ( ) Ref.: H.v. Gersdorff, QM1999 proceedings p.697c

Masashi Kaneta, LBNL Thermal(Kinetic) freeze-out Thermal freeze-out at RHIC Temperature is similar or less than at SPS Larger radial flow than at SPS STAR (  s NN =130 GeV) Hydrodynamical model: E. Schnedermann et al. PRC48(1993)2462 m T -mass [GeV/c 2 ] mass [GeV/c 2 ] Inverse slope parameter [GeV/c 2 ]

Masashi Kaneta, LBNL Thermal(Kinetic) freeze-out

Masashi Kaneta, LBNL Thermal freeze-out Hydro fit for RHIC and SPS data Hydro model: E. Schnedermann et al., PRC48(1993)2462 p  0.1 K+K+   KK p SPS 158GeV Pb+Pb, NA44 top 4% m T -mass [GeV] Note: Hydro fit is done by only STAR data. PHENIX data is superimposed on the plot

Masashi Kaneta, LBNL Ratios

Masashi Kaneta, LBNL p/p ratio Minimum bias data Systematic errors<10% for both No or weak p T and rapidity dependence rapidity STAR submitted

Masashi Kaneta, LBNL and ~0.84  /event, ~ 0.61  /event V0V0 Mixed event Higher statistics than V0 method (~10 times/event) Invariant mass [GeV] Top 15% central event Minimum Bias (150K event) 0<p<2GeV/c STAR submitted

Masashi Kaneta, LBNL / ratio No significant p T dependence in the ratio The mean ratio = 0.72±0.04 From 200 K Central trigger Au+Au Events (top ~15% multiplicity.) Systematic errors are under evaluation |y|<0.5  ratio

Masashi Kaneta, LBNL K + /K  ratio ratio p T [GeV/c] STAR Preliminary |y|<0.5 Event fraction = top 7%

Masashi Kaneta, LBNL  + and  -

Masashi Kaneta, LBNL Centrality dependence of ratios An effect of anti-baryon absorption in central collisions? (n ch /n max )  /  Preliminary     Preliminary P e r i p h e r a l  C e n t r a l p/p submitted to PRL p T GeV/c |y|<0.3 Only statistic errors are shown Systematic errors p/p : 10%  and     : under evaluation

Masashi Kaneta, LBNL Centrality dependence of ratios (cont.) K + /K  ratio seems to be independent of centrality in each measurement STAR preliminary dE/dx Kinks STAR preliminary p T < 0.35 GeV/c # primary track dN  /d  K + /K  ratio P e r i p h e r a l  C e n t r a l

Masashi Kaneta, LBNL K  /  and p/  ratios K - /  -, p/  - enhanced by ~2 in central vs. peripheral collisions p / K  ~ constant In central collisions: K - /  -  15% p/  -  8% P e r i p h e r a l  C e n t r a l

Masashi Kaneta, LBNL K *0 K + + - Central events (top 14%) primary tracks: K +  - K* signal m K *0 =  [GeV]   K *0 =  [GeV]  (stat. error only) PDG  m K *0 =  [GeV]   K *0 =  [GeV] Background estimate:  20% Breit-Wigner

Masashi Kaneta, LBNL K *0 K - + + Central events (top 14%) primary tracks: K -  + K* signal m K *0 =  [GeV]   K *0 =  0.011[GeV]  (stat. error only) PDG  m K *0 =  [GeV]   K *0 =  [GeV] Background estimate:  18% Breit-Wigner

Masashi Kaneta, LBNL K *0 The first measurement of K *0 in heavy ion collisions K *0 /h  (K *0 +K *0 )/2 / h  Centrality h  /h  max  K *0 /h  STAR preliminary Only statistical errors are shown Systematic error ~ 25% |y|< <p T <2.0 GeV/c pp (  s=63GeV) : K *0 /  e + e  (  s=91GeV) : K *0 /  h  : |  |<0.5 p T >0.1 GeV/c P e r i p h e r a l  C e n t r a l

Masashi Kaneta, LBNL Summary of ratios Anti-particle/particle ratio is flat as a function of p T Anti-baryon/baryon ratio is larger than at SPS, but not baryon free at mid-rapidity at RHIC (stat.) (sys.) (Event fraction) p/p =0.60  0.02  0.06 (top6%)  /  (M.B. trig.) =0.70  0.02 (top8%)  /  (central trig.) =0.72  0.04 (top15%)    - =0.82  0.08 (top15%) K + /K - (kink) =1.17  0.07 (top15%) K + /K - (dE/dx) =1.14  0.01  0.06 (top6%) K - /  - =0.15  0.02 (top6%) p/  - =0.080  (top6%) K *0 /h - =0.060   (top15%) K *0 h - =0.058   (top15%)

Masashi Kaneta, LBNL Chemical freeze-out model Comparable particle ratios to experimental data q: 1 for u and d, -1 for u and d  q : lightquark chemical potential s: 1 for s, -1 for s  s : strangeness chemical potential Particle density of each particle Decay all resonances g : spi-isospin freedom

Masashi Kaneta, LBNL Chemical freeze-out Baryonic Potential  B (=3  q ) [MeV] Chemical Temperature T ch [MeV] AGS SIS LEP/ SppS SPS quarks-gluons hadrons RHIC Experimental ratio Model prediction of ratio

Masashi Kaneta, LBNL Probe of spatial and momentum correlation Coalescence parameters related to source size where V is effective volume Expect   1 ( freeze-out at constant density) Anti-Nucleosynthesis via coalescence

Masashi Kaneta, LBNL Anti-Nucleus Measurements in STAR PID via ionization in TPC (dE/dx)

Masashi Kaneta, LBNL d,d Coalescence excitation function Decrease in B 2 between SPS and RHIC Assuming B 2  1/V, 123±77% increase in volume relative to SPS

Masashi Kaneta, LBNL t, 3 He, 3 He excitation function Assuming B 3  (1/V) 2, 147±97% increase in volume relative to SPS (average of 3 He and 3 He)

Masashi Kaneta, LBNL m T systematics (, ) Radius parameter [fm] m T [GeV] The dashed line is a fit for  HBT radii Using static Gaussian model (W.Llope et al.) R G =6.83  0.21 (stat.)  0.57 (sys.) [fm]

Masashi Kaneta, LBNL Summary of Anit-Nucleosynthesis Copious Anti-Nucleus production at RHIC measured by STAR First measurements of d and 3 He production Future possibilities for first observation of  and beyond Initial coalescence parameters from d and 3 He Roughly factor of 2 increase in Anti-Nucleon freeze-out volume relative to SPS

Masashi Kaneta, LBNL HBT

Masashi Kaneta, LBNL Particle correlations (HBT) Size parameters Transverse and longitudinal direction Duration time From R out and R side Phase space density Combination of radius parameter and yield

Masashi Kaneta, LBNL HBT Pion HBT Centrality Transverse momentum The HBT excitation function Phase space density Event-by-Event HBT K 0 s K 0 s,  pp, pp  correlations Non-identical particles Many topics in STAR measurement

Masashi Kaneta, LBNL 1D analysis The simplest parameterization: STAR preliminary     : |y|< < p T (GeV/c) < [fm]  w/ Coulomb correction  w/o Coulomb correction

Masashi Kaneta, LBNL 3D analysis Information: source size duration time (for transparent sources) Pratt-Bertsch Parameterization (measured in the LCMS frame; (p 1 + p 2 ) z =0) p1p1 q Out p2p2 q Side x y p 1+ p 2

Masashi Kaneta, LBNL 3 Dimensional   -  - HBT Top 12% central events 0.125<p T <0.225 [GeV/c] |y|<0.5 1D Projections of the 3D Pratt-Bertsch Parameterization q Side,q Long <20MeV/c q Out,q Long <20MeV/c Systematic error result from the pair cuts (merging) and Coulomb correction C(q out ) C(q Side ) q out [GeV/c] q Side [GeV/c] C(q Long ) q Long [GeV/c] q Out,q Side <20MeV/c [fm]  Coulomb corrected with a 5 fm source  No Coulomb correction (sta.) (sys.)

Masashi Kaneta, LBNL Coulomb correction Gamow Standard Coulomb 5-dimensional Monte-Carlo integration of Coulomb wave functions over a spherical source { S.Pratt et al.,Phys.Rev. C42(1990)2646 } Damped Coulomb ( <1) particle misidentification long lived resonances “Standard” Coulomb CC No Coulomb CC 0 < f < 1 Size dependence Damping dependence

Masashi Kaneta, LBNL Centrality dependence GeV/c < p T <0.225 GeV/c  tot: 32-72% 12-32% 0-12% STAR Preliminary  +  +,  -  -, parameters similar `s don’t change with multiplicity radii increase with multiplicity roughly similar to AGS/SPS Comparison with AGS/SPS parameters roughly same similar increase in R Out, R Side (geometric effect) sys. error

Masashi Kaneta, LBNL m T dependence 12 % most central events 0.125<p T <0.225 [GeV/c] STAR Preliminary 0.225<p T <0.325 [GeV/c] 0.325<p T <0.450 [GeV/c]  +  +,  -  - HBT parameters similar with increasing m T increases  fewer resonances radii decrease  position-momentum correlations Comparison with AGS/SPS parameters roughly similar to AGS/SPS With increasing m T similar increase in similar decrease of radii stronger effect in R Out than at AGS/SPS STAR Preliminary sys. error

Masashi Kaneta, LBNL The HBT excitation function Compilation 3D  -HBT parameters as a function of  s ~10% Central Au+Au(Pb+Pb) events y ~ 0 k T  0.17 GeV/c STAR Preliminary No significant jump from SPS to RHIC We need energy scan between both energy

Masashi Kaneta, LBNL Summary of correlations The first measurement of interferometry at RHIC Source sizes roughly same as at AGS/SPS ( < 10fm) Radii increase with centrality (expected for R Out,R Side ) Radii decrease with increasing k T Indicate strong flow R Out /R Side = ~ 1 to <1 explosive source opaque source? The “universal” phase space density observed at SPS holds at RHIC

Masashi Kaneta, LBNL Event Anisotropy

Masashi Kaneta, LBNL Event anisotropy The pressure gradient generates collective motion (aka flow) Central collisions radial flow Peripheral collisions radial flow and anisotropic flow Momentum space Almond shape overlap region in coordinate space x z y

Masashi Kaneta, LBNL Charged particle v 2 versus centrality PRL 86, (2001) 402 |  | < < p T < 2.0 Boxes show “initial spatial anisotropy”  scaled by n ch = primary tracks in |  | < 0.75

Masashi Kaneta, LBNL Excitation function WA98  NA49  h-h-

Masashi Kaneta, LBNL Charged  and p+p, v 2 (p T ) (M.B.)

Masashi Kaneta, LBNL A Hydro view of the world Hydro calculations: Huovinen, Kolb and Heinz

Masashi Kaneta, LBNL Charged  v 2 (p t ) for different centralities

Masashi Kaneta, LBNL Charged particle anisotropy 0<p T <4.5 GeV/c Only statistical errors Systematic error 10% - 20% for p t = 2 – 4.5 GeV/c

Masashi Kaneta, LBNL Summary of Event anisotropy Large v 2 an indication of early thermalization v 2 at low p T quantitative agreement with hydrodynamic model predictions for mid-central collisions Mass dependence of v 2 (p T ) agreement with hydro calculations Around p T > 2GeV/c the data starts to deviate from hydro

Masashi Kaneta, LBNL Summary of talk The first results from  s NN =130 GeV Au+Au collisions are presented by STAR Single particle spectra ,K,p, strangeness baryons and resonances Particle correlations  HBT Event anisotropy Charged hadron up to 4.5GeV/c pion and proton

Masashi Kaneta, LBNL Conclusions Net-baryon  0 at mid-rapidity! Anti-baryon/baryon ratios are toward 1, but still <1 Chemical Freeze-out T ch ~ 200 GeV ( SPS, AGS)  B ~ 50 MeV ( SPS, AGS) Large anisotropic flow Hydro model can describe v 2 an low p T (<2GeV/c) Large v 2  early thermalization Thermal Freeze-out Strong space-momentum correlations Large radial flow ~ 0.6c(SPS/AGS = c) T fo = MeV (similar to SPS/AGS)