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First results from STAR experiment at RHIC

This article presents the first results from the STAR experiment at RHIC, focusing on the study of the Quark-Gluon Plasma. The experiment involves multiple institutions from different countries and utilizes various detectors and technologies.

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First results from STAR experiment at RHIC

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

  2. RHIC'S ULTIMATE GOAL:QUARK-GLUON PLASMA

  3. Brookhaven National Lab.

  4. The STAR collaboration ~ 400 collaborators 34 institutions 7 countries

  5. 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

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

  7. 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

  8. Mating the OFC & Gas Vessel • WindingOuter Field Cage • Mating OFC & Gas Vessel • OFC Check • Moving the Central Membrane

  9. The STAR TPC Under Construction at LBL • First Successful Mating of: • Gas Vessel • Outer Field Cage • Sector Wheels • Central membrane

  10. The TPC arrives at BNL from LBL on11/6/97

  11. 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

  12. Au+Au, sNN=130 GeV Central Event From real-time Level 3 display. Data Taken June 25, 2000. ~2000 tracks per event

  13. Particle identification by dE/dx p dE/dx [keV/cm] K p e |p/Z| [GeV/c]

  14. Focus on • Hadrons • Measured : h-, p ±, K±, K0s, K*0, K*0, p, p, d, 3He, 3He, t,L, L, X -, X + • In future :g, p 0,f,W -+W -,r, w, h, h’, D, L(1520), S(1385), J/ and more • Freeze-out conditions of low momentum hadrons by: • Spectra/Ratios • Thermal/Chemical Freeze-out • Particle correlations • Size parameters • Event anisotropy • v2

  15. Spectra

  16. Spectra • Low pT spectra • h-, p, K, p  Thermal freeze-out • High pT spectra • h-  hard process • Particle ratios, yield (dN/dy, dN/dh) • p/p, L/L, X+/X-, K+/K-, K-/p-, p/p-, K*0/h- • Stopping • Chemical freeze-out • d/p • Coalescence

  17. h- multiplicity • 6% systematic error shown on 3 points only Preliminary ZDC pulse height 5% Central CTB pulse height

  18. h- centrality dependence 40% 30% 20% 10% 5%

  19. h- centrality dependence(cont.) STAR, Preliminary 15% Increase in <pT> from 80% sample to top 5% central STAR, Preliminary NA49 UA1

  20. h- pT distribution STAR Preliminary STAR Preliminary Statistical errors negligible Errors on points: systematic error on STAR data Gray bars: cumulative error including UA1 scaling Hard: Binary collisions TAA = 26 ± 2 mb-1 Soft: Wounded nucleon

  21. Particle Identification • dE/dx • e, p, K, p • Kink, V0, Mixed event • Kaon to muon decay • L, X, W, g, p0, etc. • Resonances p  K d e Vo “kinks”: K  + 

  22. g and p0 STAR Preliminary p0 gg invariant mass [GeV] • The e+e- pair from g conversion is measured • Large g acceptance • pT = 50 MeV/c to ~4 GeV/c, |h|<1.8 Typical e+e-pair from g e+ e+ e- e- e- e+ e- e+

  23. f  K+K- f

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

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

  26. Kink K • Kaon from muon decay m nm K Inverse slope: 2675(sta.)10(sys.) MeV Inverse slope: 2725(sta.)10(sys.) MeV |y|<0.5 Event fraction = top 7% |y|<0.5 Event fraction = top 7% K+ K- STAR Preliminary STAR Preliminary

  27. “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.)

  28. mT distribution from Hydrodynamical model bs R • Cylindrical source • Flow profile included 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

  29. Thermal(Kinetic) freeze-out STAR (sNN=130 GeV) Hydrodynamical model: E. Schnedermann et al. PRC48(1993)2462 mT-mass [GeV/c2] • Thermal freeze-out at RHIC • Temperature is similar or less than at SPS • Larger radial flow than at SPS Inverse slope parameter [GeV/c2] mass [GeV/c2]

  30. Ratios

  31. p/p ratio • Minimum bias data • Systematic errors<10% for both • No or weak pT and rapidity dependence STAR submitted STAR submitted rapidity

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

  33. L/L ratio • No significant pT dependence in the ratio • The mean ratio = 0.72±0.04 |y|<0.5 L/L ratio • From 200 K Central trigger Au+Au Events (top ~15% multiplicity.) • Systematic errors are under evaluation

  34. K+/K- ratio ratio STAR Preliminary |y|<0.5 Event fraction = top 7% pT [GeV/c]

  35. X+ and X-

  36. Centrality dependence of ratios • An effect of anti-baryon absorption in central collisions? L/LPreliminary X+/X-Preliminary p/p submitted to PRL pT 0.6-0.8 GeV/c |y|<0.3 Only statistic errors are shown Systematic errors p/p : 10% L/L and X+/X- : under evaluation (nch/nmax) P e r i p h e r a l  C e n t r a l

  37. Centrality dependence of ratios(cont.) • K+/K- ratio seems to be independent of centrality in each measurement Kinks dE/dx STAR preliminary STAR preliminary pT < 0.35 GeV/c K+/K- ratio K+/K- ratio P e r i p h e r a l  C e n t r a l P e r i p h e r a l  C e n t r a l dN-/dh # primary track

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

  39. K*0K++- • Central events (top 14%) • primary tracks: K+- • K* signal • mK*0 = 0.8930.003 [GeV] • K*0 = 0.058 0.015 [GeV] • (stat. error only) • PDG • mK*0 = 0.89610.00026 [GeV] • K*0 = 0.05070.0006 [GeV] • Background estimate: •  20% Breit-Wigner

  40. K*0K-++ • Central events (top 14%) • primary tracks: K-+ • K* signal • mK*0 = 0.8960.004 [GeV] • K*0 = 0.063 0.011[GeV] • (stat. error only) • PDG • mK*0 = 0.89610.00026 [GeV] • K*0 = 0.05070.0006 [GeV] • Background estimate: •  18% Breit-Wigner

  41. K*0 • The first measurement of K*0 in heavy ion collisions (K*0 +K*0)/2 / h- STAR preliminary • K*0/h- Only statistical errors are shown Systematic error ~ 25% • K*0/h- |y|<0.5 0.2<pT<2.0 GeV/c pp (s=63GeV) : K*0/p K*0/h- e+e-(s=91GeV) : K*0/p P e r i p h e r a l  C e n t r a l h-: |h|<0.5 pT>0.1 GeV/c Centrality h-/h-max

  42. Summary of ratios (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%) X+/X-= 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-/p- =0.15  0.02(top6%) p/p- =0.080  0.008(top6%) K*0/h-= 0.060  0.006  0.015(top15%) K*0h-= 0.058  0.006  0.015 (top15%) • Anti-particle/particle ratio is flat as a function of pT • Anti-baryon/baryon ratio is larger than at SPS, but not baryon free at mid-rapidity at RHIC

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

  44. Chemical freeze-out 250 Model prediction of ratio LEP/ SppS quarks-gluons RHIC 200 SPS 150 AGS Chemical Temperature Tch [MeV] Experimental ratio 100 SIS 50 hadrons 0 0 200 400 600 800 1000 1200 Baryonic Potential B(=3q) [MeV]

  45. HBT

  46. Particle correlations (HBT) • Size parameters • Transverse and longitudinal direction • Duration time • From Rout and Rside • Phase space density • Combination of radius parameter and yield

  47. HBT Many topics in STAR measurement • Pion HBT • Centrality • Transverse momentum • The HBT excitation function • Phase space density • Event-by-Event HBT • K0s K0s, LL • pp, pp • ppp correlations • Non-identical particles

  48. 3D analysis Pratt-Bertsch Parameterization (measured in the LCMS frame; (p1+ p2)z=0) p1+p2 y qOut • Information: • source size • duration time(for transparent sources) qSide p2 p1 x

  49. 3 Dimensional -- - HBT qOut,qSide<20MeV/c C(qLong) qLong [GeV/c] 1D Projections of the 3D Pratt-Bertsch Parameterization qSide,qLong<20MeV/c qOut,qLong<20MeV/c C(qout) C(qSide) Top 12% central events 0.125<pT<0.225 [GeV/c] |y|<0.5 qout [GeV/c] qSide [GeV/c] • Coulomb corrected with a 5 fm source • No Coulomb correction [fm] [fm] [fm] Systematic error result from the pair cuts (merging) and Coulomb correction (sta.) (sys.)

  50. Centrality dependence 0.125 GeV/c < pT <0.225 GeV/c STAR Preliminary • ++, --,parameters similar • `s don’t change with multiplicity • radii increase with multiplicity • roughly similar to AGS/SPS sys. error • Comparison with AGS/SPS • parameters roughly same • similar increase in ROut, RSide • (geometric effect) tot:32-72% 12-32% 0-12%

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