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Pion HBT in Cu+Cu Collisions at RHIC

Pion HBT in Cu+Cu Collisions at RHIC. Sergey Panitkin Brookhaven National Lab STAR Collaboration. Outline. Introduction and motivation Experimental details Analysis results Comparison to AuAu @ 200 GeV Comparison to theoretical predictions Summary. Identical meson correlations.

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Pion HBT in Cu+Cu Collisions at RHIC

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  1. Pion HBT in Cu+Cu Collisions at RHIC Sergey Panitkin Brookhaven NationalLab STAR Collaboration Sergey Panitkin

  2. Outline • Introduction and motivation • Experimental details • Analysis results • Comparison to AuAu @ 200 GeV • Comparison to theoretical predictions • Summary Sergey Panitkin

  3. Identical meson correlations Decompose q into components: qLong: in beam direction qOut : in direction of transverse momentum KT qSide:  qLong & qOut Radii are related to source variances: Sensitive to emission time Sensitive to transverse extent Sensitive to longitudinal extent In Longitudinally Co-Moving System (LCMS) bl =0 Sergey Panitkin

  4. Rischke & Gyulassy, NPA 608, 479 (1996) with transition Femtoscopic signature of QGP G. Boyd et al., , Nucl.Phys. B469 (1996) 419 3D 1-fluid Hydrodynamics “” • Long-standing favorite signature of QGP: • Lattice QCD -> Speed of sound goes to zero (pressure drop) at phase transition • increase in , ROUT/RSIDEdue to deconfinement  confinement transition • hoped-for “turn on” as QGP threshold is reached (“softest point”) Sergey Panitkin

  5. Energy dependence of pion HBT • AuAu (PbPb) • Y~0 • <Kt>~170 MeV • Central ~10% RHIC HBT Puzzle #1 Smooth energy dependence Where is the softest point ? Lower energies? Lighter systems? Sergey Panitkin

  6. STAR 200 GeV Cu+Cu Min. biasstatistics • Total: 64.47 Mevts of Min-bias • Min bias Trigger was operational for 52 days. ~5M events used for this analysis Ave/day ~ 1.24 Mevts Sergey Panitkin

  7. Centrality selection in Cu+Cu Collisions 60% 50% 40% 30% 20% 10% 1 2 3 4 5 6 Reference multiplicity in TPC |y|<0.5 Sergey Panitkin

  8. Centrality dependence of the Kt dependence Cu+Cu @ 200 GeV, positive pions STAR preliminary Ro Rl Rs Radii decrease for less central events Radii decrease with Kt (consistent with flow) Lambda parameter grows with Kt Sergey Panitkin

  9. Comparison to Au+Au at 200 GeV STAR preliminary Most central: AuAu 0 - 5% CuCu0 – 10% Sure, Cu is smaller than Au ! Sergey Panitkin

  10. Expansion in Heavy Ion Collisions • x2 expansion in AuAu • Cu bridges dAu and AuAu Sergey Panitkin

  11. Multiplicity scaling of pion radii at RHIC STAR preliminary • CuCu bridges multiplicity range • between dAu andAuAu • Radii scale with multiplicity from • peripheral dAu to central AuAu • Scaling holds with Kt • 62 GeV AuAu data follow the same • systematics Sergey Panitkin

  12. Cramer-Miller predictions for Cu+Cu nucl-th/0507004 See talk by JohnCramer First prediction of HBT Radii for Cu+Cu STAR preliminary Kt Kt Scaled AuAu space-time parametersby (63/197)1/3 works? Sergey Panitkin

  13. Summary • First HBT measurements in Cu+Cu collisions at RHIC at 200 GeV • Preliminary pion HBT radii in Cu+Cu show clear centrality and Kt dependence, similar to Au+Au • Expansion in heavy ion collisions • Multiplicity scaling of pion (Nch1/3 ) radii is observed, similar lower (AGS, SPS ) energies • Consistent with no change in dynamics between CuCu and AuAu Sergey Panitkin

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