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The STAR Experiment at RHIC: What have we learnt so far?

The STAR Experiment at RHIC: What have we learnt so far?. RHIC Run 2000 The STAR Detector Results and their Interpretation Inclusive Particle Spectra and Ratios HBT and Elliptic Flow Hard Probes Summary and Outlook. Rochester NSRL, NY April 17, 2001. Don’t Panic!!!.

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The STAR Experiment at RHIC: What have we learnt so far?

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  1. The STAR Experiment at RHIC:What have we learnt so far? RHIC Run 2000 The STAR Detector Results and their Interpretation InclusiveParticle Spectra and Ratios HBT and Elliptic Flow Hard Probes Summary and Outlook Rochester NSRL, NY April 17, 2001

  2. Don’t Panic!!! - New Scientist most dangerous event in human history: - ABC News –Sept ‘99 "Big Bang machine could destroy Earth" -The Sunday Times – July ‘99 No… the experiment will not tear our region of space to subatomic shreds. - Washington Post – Sept ‘99 the risk of such a catastrophe is essentially zero. – B.N.L. – Oct ‘99 Apocalypse2 – ABC News – Sept ‘99 Will Brookhaven Destroy the Universe? – NY Times – Aug ‘99 Thomas Ullrich

  3. Baryon Stopping/Transport Anti-baryons - all from pair production Baryons - pair production + transported B/B ratio = 1 - Transparent collision B/B ratio ~ 0 - Full stopping, little pair production Measure p/p, L/L , K-/K+ (uud/uud) (uds/uds) (us/us) _ _ _ _ - - - - - - - - Thomas Ullrich

  4. Measure D=1.08± 0.08 Simple Model/Quark Coalescence Assume fireball passes through a deconfined state can estimate particle ratios by simple quark-counting models No free quarks so all quarks have to end up confined within a hadron Predict D=1.12 Predict D=1.12 System consistent with having a de-confined phase Thomas Ullrich

  5. Particle Ratios and Chemical Content mj= Quark Chemical Potential T = Temperature Ej – Energy required to add quark gj– Saturation factor Use ratios of particles to determine m, Tchand saturation factor Thomas Ullrich

  6. 1D: overall rough “size” y1 x1 K y2 ~1 m x2 Rout Rside Measuring the Source “Size” (HBT) ~5 fm 3D decomposition of relative momentum provides handle on shape and time as well as size Thomas Ullrich

  7. Particle Ratios at RHIC • All ratios for: • central collisions •  = 0 p/p = 0.6  0.02 (stat.)  0.06 (sys.) / = 0.73 ± 0.03 (stat.) X+/X- = 0.82 ± 0.08 (stat.) K-/K+(kink) = 0.87 ± 0.02(stat.) ± 0.05(sys.) K-/K+(dE/dx) = 0.89±0.008 (stat.) ± 0.05 (sys.) K-/p- =0.15 ± 0.02 (stat.) K*/h-= 0.06 ± 0.006 (stat.)± 0.01 (sys.) K*/h-= 0.058 ± 0.006 (stat.) ± 0.01 (sys.) Thomas Ullrich

  8. Radial Flow: mt - Slopes vs. Mass Naïve: T = Tfreeze-out + m  r 2 where  r  = averaged flow velocity STAR • Increased radial flow at RHIC ßr (RHIC) = 0.6c  ßr (SPS/AGS) = 0.4 - 0.5cTfo (RHIC) = 0.1-0.12 GeV  Tfo (SPS/AGS) = 0.12-0.14 GeV Thomas Ullrich

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