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Quarkonium Physics with STAR

This presentation by Mauro Cosentino from the University of São Paulo/BNL delves into the physics of quarkonium in the context of the STAR experiment. It discusses the phenomenon of melting in QCD plasma, suppression of quarkonium states due to color screening, and how these effects are influenced by temperature and binding energy. The use of the STAR Detector's particle identification techniques, including the TPC and BEMC, for analyzing J/ψ and Υ states is detailed. Results from Au+Au and p+p collisions provide insights into the properties of the quark-gluon plasma (QGP).

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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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