1 / 13

 production in p+p and Au+Au collisions in STAR

Debasish Das UC Davis (For the STAR Collaboration) ‏.  production in p+p and Au+Au collisions in STAR. Quarkonia and the concept of suppression. Charmonia : J/  ,  ’,  c Bottomonia :  (1S),  (2S),  (3S) ‏. Heavy quarks carry the information of early stage of collisions:

benson
Download Presentation

 production in p+p and Au+Au collisions in STAR

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Debasish Das UC Davis (For theSTAR Collaboration)‏  production in p+p and Au+Au collisions in STAR

  2. Quarkonia and the concept of suppression Charmonia: J/, ’, cBottomonia:  (1S), (2S), (3S)‏ • Heavy quarks carry the information of early stage of collisions: • Charm and bottom quarks are massive. • Formation takes place early only in the collision. • Proposed Signature : QCD phase transition • Color screening of static potential between heavy quarks: J/suppression: Matsui and Satz, Phys. Lett. B 178 (1986) 416 • Suppression of states is determined by TC and their binding energy Lattice QCD: Evaluation of spectral functions  Tmelting • Deconfinement  Color screening heavy quarkonia states “dissolved” • Tdiss(’)  Tdiss(c)< Tdiss((3S)) < Tdiss(J/)  Tdiss((2S)) < Tdiss((1S))‏ Their suppression pattern is a thermometer of the QCD matter produced. H. Satz, HP2006 2/17

  3.  States in RHIC S), S), S)‏ (1S) no melting at RHIC  standard candle (reference)‏ (2S) likely to melt at RHIC (analogous to J/)‏ (3S) melts at RHIC (analogous to ’)‏ • Pros • co-mover absorption is very small ( C.M.Ko PLB 503, 104)‏ • recombination negligible at RHIC (bb << cc)‏ • STAR has efficient trigger and large acceptance Cons • extremely low rate 10-9/min. bias pp interaction • need good resolution to separate three S-states  measurements at RHIC  challenge to understand such rare probes

  4. STAR  Mass Resolution • STAR detector is able to resolve individual states of  albeit Bremsstrahlung • With current low statistics, yield is extracted from combined (1S+2S+3S) states • FWHM ~ 400 MeV/c2 With Inner Tracker : small X/X0~6% W/o Inner Tracker : Low X/X0

  5. STAR Detectors used for  measurements Au+Au  Event in STAR Trigger. • EMC • Acceptance: || < 1 , 0 <  < 2 • High-energy tower trigger  enhance high-pT sample • Essential for quarkonia triggers •  trigger  enhances electrons • Use TPC for charged tracks selection • Use EMC for hadron rejection • Electrons identified by dE/dx ionization energy loss in TPC • Select tracks with TPC, match to EMC towers above 3 GeV

  6. STAR  Trigger (p+p 200 GeV in Run 6)‏ Sample -triggered Event • e+e- • mee = 9.5 GeV/c2 • cosθ = -0.67 • E1 = 5.6 GeV • E2 = 3.4 GeV charged tracks • Full EMC acceptance |η|<1 in run 6 • Integrated luminosity ≈ 9 pb-1 in run 6

  7. STAR  Trigger (Au+Au 200 GeV in Run 7)‏ Sample -triggered Event • e+e- • mee = 9.5 GeV/c2 (offline mass)‏ • cosθ = -0.77(offline opening angle)‏ • E1 = 6.6 GeV (online cluster energy hardware trigger)‏ • E2 = 3.2 GeV (online cluster energy software trigger)‏ Electron Momentum > 3 GeV/c • Full EMC acceptance |η|<1 in Run 7 • Integrated luminosity ≈ 300μb-1in Run 7 Challenging analysis!!!!! charged tracks

  8. QM 2006: in Run 6 p+p at √s=200 GeV: Invariant Mass preliminary preliminary • Signal + Background  unlike-sign electron pairs • Background  like-sign electron pairs (1S+2S+3S) total yield: integrated from 7 to 11 GeV from background-subtracted mee distribution • Peak width consistent with expected mass resolution • Significance of signal is 3σ • Note: Contribution from Drell-Yan (~9%) ignored

  9. QM 2006 : STARvs. Theory and World Data preliminary STAR 2006 √s=200 GeV p+p ++→e+e- cross section consistent with pQCD and world data

  10.  in Au+Au at √s = 200 GeV (Run 7)‏ First Rough Look: Using identical cuts as in p+p analysis. Pros : allows “apples-to-apples” comparison with p+p Cons : not optimal for Au+Au – larger background, different trigger thresholds RAA: Upper Limit  RAA< 1.3 at 90% CL

  11.  in Au+Au at √s = 200 GeV (Run 7)‏ Improved Analysis: Pros: improved EMC-track-trigger handling  strong signal and enhanced S/B Cons: trigger efficiency and systematic checks not completed yet • Strong 4 signal • First measurement of  in nucleus-nucleus collisions ever • Too early for RAA but will provide good first measurement • also need re-analysis of p+p

  12. Summary and Outlook • Full EMC + trigger  quarkonium program in STAR • Run 6: firstmid-rapidity measurement of S+2S+3S)→e+e- cross section at RHIC in p+p collisions at √s=200 GeV • Bee×(dσ/dy)y=0=91±28(stat.)±22(syst.) pb • STAR  in p+p measurement is consistent with pQCD and world data • Run 7: We have the first measurement in heavy ion collisions for 200 GeV Au+Au • Strong signal • Soon: • RAA of  • Run 8: measurement in d+Au • Absolute cross-section in p+p, d+Au, and Au+Au • RHIC II : 20 nb-1 will allow separation of 1S, 2S, 3S states

  13. Thanks!!!

More Related