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First Measurement of  Suppression

First Measurement of  Suppression. Rosi Reed (UC Davis) for the STAR Collaboration. Motivations. 1/  r  [fm -1 ]. T/T C.  (1S). 2.  b (1P). 1.2. J/ (1S) (2S).  b ’(2P)  (3S).  T C.  c (1P)  (2S).

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First Measurement of  Suppression

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  1. First Measurement of Suppression Rosi Reed (UC Davis) for the STAR Collaboration

  2. Motivations 1/r[fm-1] T/TC (1S) 2 b(1P) 1.2 J/(1S) (2S) b’(2P) (3S) TC c(1P) (2S) Sequential suppression of Quarkoniummesons acts as a QGP thermometer. ] A. Mocsy and P.Petreczky, PRL 99, 211602 (2007) Expectation at 200 GeV (1S)does notmelt (2S)is likelyto melt (3S)willmelt Rosi Reed - Quarkmatter 2011

  3.  at STAR TPC || < 1, 0 <  < 2 Tracking  momentum dE/dx  electron ID • Decay channel:e+e− • Pros • Small background at M~10 GeV/c2 • Co-mover absorption is small at 200 GeV • Recombination negligible at 200 GeV • Large Acceptance • Fast Trigger • Cons • Low rate of 10-9 per minbiaspp interaction • Good resolution needed to separate 3 S-states BEMC || < 1, 0 <  < 2 E/p  electron ID High-energy tower trigger

  4. Trigger and Analysis High Tower ET > 3.5 GeV (pp) > 4.0 GeV (AuAu) E1 Cluster Phys. Rev. D 82 (2010) 12004 L0 Trigger Tower L2 Parameters (pp only) E1 Cluster, E2 Cluster, Cos(q), Invariant Mass q p+p cross-section TPC tracks are extrapolated to trigger clusters E2 Cluster E/p and dE/dx used to select e+ and e- tracks Rosi Reed - Quarkmatter 2011

  5.  Yield 0-60% Centrality Raw yield of e+e- with |y|<0.5 = 196.6 ±35.8 = N+- - N-- - N++ - ∫DY+bb Drell-Yan+bb = n = 4.59, m0 = 2.7 Rosi Reed - Quarkmatter 2011

  6.  Yield by centrality • System uncertainties • p+p luminosity and bbc trigger efficiency •  Line-shape • Drell-Yan and bb background Peripheral Mid-Central Central Rosi Reed - Quarkmatter 2011

  7. (1S+2S+3S) RAA Rosi Reed - Quarkmatter 2011

  8. Conclusions • (1S+2S+3S) is suppressed in central collisions! 3saway from RAA = 1 • RAA(0-60%)=0.56±0.11(stat)+0.02/-0.14(sys) • RAA (0-10%)=0.34±0.17(stat)+0.06/-0.07(sys) • 3x the p+p statistics (run 9) + ~2x the Au+Au statistics (run 11) will decrease the uncertainty • Additional 33% statistical and 11.4% systematic due to uncertainties on p+p cross-section Rosi Reed - Quarkmatter 2011

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