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

2 Why Quarkonia ? Using F 1 : S. Digal, P. Petreczky, H. Satz, Phys. Lett. B514 (2001) 57 Using V 1 : C.-Y. Wong, hep-ph/ –Key Idea: Melting in the plasma Suppression of states is determined by T C 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 : Need: Electron ID Hadron Rejection Trigger Typical electron p range for: J/  : 1-3 GeV/c  : > 3.5 GeV/c

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/  Trigger 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 Level-2 (software): Full EMC tower data available Towers clustering → E e CTB matching (veto photons) Vertex: BBC resolution ~6cm for Au+Au, 30cm for p+p Invariant mass assuming straight tracks: m 2 inv  2E 1 E 2 [1-cos(  12 )] Trigger for m inv > 2.5 GeV/c 2 Decision is taking up to 500  s This J/  trigger setup is efficient only for p+p Au+Au will require ToF upgrade

7  Trigger Implementation L0 Trigger –Simple single high tower trigger E T >3.5 GeV L2 Trigger –Use similar L2 to J/  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, 2  & |  |<1

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

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

10 Cu+Cu analysis The same analysis for p+p was applied to 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.

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12 STAR Contribution Large Acceptance at Mid-Rapidity –|  |<1, 0<  <2  –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/  trigger in p+p only, need large min. bias. dataset in Au+Au

13 Efficiency and Purity of the Id

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

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

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

17 Origin of J/  suppression on SPS Assume: 1.N J/  (observed) = 0.6 N J/  N  c (compatible w Hera-B data) 2.J/  doesn’t melt  c dissociation =  ’ dissociation Right or wrong, it shows how important the missing cc measurement is! F. Karsch, D. Kharzeev, H. Satz, hep-ph/

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