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Quarkonium Physics with STAR

Quarkonium Physics with STAR. Mauro Cosentino (University of Sao Paulo/BNL). Using F 1 : S. Digal, P. Petreczky, H. Satz, Phys. Lett. B514 (2001) 57. Using V 1 : C.-Y. Wong, hep-ph/0408020. Why Quarkonia ?. Key Idea: Melting in the plasma

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Quarkonium Physics with STAR

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  1. Quarkonium Physics with STAR Mauro Cosentino (University of Sao Paulo/BNL)

  2. Using F1: S. Digal, P. Petreczky, H. Satz, Phys. Lett. B514 (2001) 57 Using V1: C.-Y. Wong, hep-ph/0408020 Why Quarkonia ? • Key Idea: Melting in the plasma • Suppression of states is determined by TC and their binding energy • Color screening  Deconfinement • QCD thermometer  Properties of QGP Is the sequential suppression pattern the smoking gun?

  3. The STAR Detector TPC: || < 1, 0 <  < 2 ToF: -1 <  < 0,  = 0.1 EMC: || < 1, 0 <  < 2 Mag.Field: 0.5 T

  4. Golden Decay Mode : Typical electron p range for: J/y: 1-3 GeV/c : > 3.5 GeV/c Need: Electron ID Hadron Rejection Trigger

  5. Electron Identification • Association of TPC and BEMC information • TPC gives dE/dx and momentum (p) • BEMC gives the energy (E) • Selected particles are within specifics dE/dx and p/E ranges.

  6. J/y Trigger Level-2 (software): • Full EMC tower data available • Towers clustering → Ee • CTB matching (veto photons) • Vertex: BBC resolution ~6cm for Au+Au, 30cm for p+p • Invariant mass assuming straight tracks: m2inv 2E1E2[1-cos(q12)] • Trigger for minv > 2.5 GeV/c2 • Decision is taking up to 500ms Level-0 (topology): • Φ divided in 6 sections • Find a tower above threshold (E > 1.2 GeV) • Look for other towers above threshold on the 3 opposite sections This J/y trigger setup is efficient only for p+p Au+Au will require ToF upgrade

  7.  Trigger Implementation • L0 Trigger • Simple single high tower trigger ET>3.5 GeV • L2 Trigger • Use similar L2 to J/y • Very efficient > 80% • Large rejection power • 100 at L0 • 100 at L2 • Luminosity limited • Works in p+p and central Au+Au • Exploit full STAR acceptance, 2p & |h|<1

  8. STAR preliminary Results J/y J/ data, Gaussian Fit and simulation line shape. Cross-section calculation being reviewed, but preliminary results consistent with pQCD calculations and PHENIX measurement.

  9. STAR preliminary Results  STAR cannot resolve different S states  (1S+2S+3S)  e+e-

  10. STAR Preliminary Cu+Cu analysis The same analysis for p+p was applied to Cu+Cu@200 GeV data, but without simulations and embedding, no cross-sections quoted No specific triggers. For the  a high-tower threshold of 3.75 GeV mimetized the L0 –trigger.

  11. Back-up Slides

  12. STAR Contribution • Large Acceptance at Mid-Rapidity • |h|<1, 0<f<2p • Pair acceptance~(single acceptance)2 • Electron identification capabilities • TPC dE/dx • EMC E>1-2 GeV (operating full barrel) • TOF p<2-3 GeV/c • Trigger capabilities on Barrel EMC • Suitable for single electron (see F. Laue’s talk) • Suitable for di-electrons(?) • Heavy-Quarkonia states are rare • : efficient trigger for all systems • J/y: trigger in p+p only, need large min. bias. dataset in Au+Au

  13. Efficiency and Purity of the Id

  14. J/y in Au+Au (Run IV) • No trigger due to high background • Dataset: Au+Au@200 GeV • Just a faint signal • For efficient J/y trigger, full barrel ToF is needed (just patch in Run IV)

  15. Scaling from Au+Au to elementary: a=1  Analysis for Au+Au: Upper Limit • 90% C.L.: signal < 4.91 • B*ds/dy C.L. < 7.6 mb • Acceptance increase will help (Factor ~4)

  16. ToF Upgrade MRPC Time of Flight Barrel in STAR 23,000 channels covering TPC & Barrel Calorimeter Construction FY 06 – FY 08 Will allow to deploy J/y trigger in Au+Au Coincidence: ToF slat + EMC tower substantially reduces photon background

  17. Origin of J/y suppression on SPS Assume: • NJ/y(observed) = 0.6 NJ/y + 0.4 Ncc (compatible w Hera-B data) • J/y doesn’t melt • cc dissociation = y’ dissociation Right or wrong, it shows how important the missing cc measurement is! F. Karsch, D. Kharzeev, H. Satz, hep-ph/0512239

  18. EXTRA: trigger pre-calibration for BEMC • Online energy resolution ~ 17%/√E • Offline energy resolution ~ 14 %/√E

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