1. Multi-strange Baryon Correlations in p+p and d+Au Collisions at √s NN = 200 GeV Betty Bezverkhny Yale University For the Collaboration Hot Quarks ’04, Taos, New Mexico

2. Betty BezverkhnyHotQuarks 20042 Why Study Identified Correlations? trigger Adler et al., PRL90:082302 (2003), STAR Previously published: N charged correlations in p+p STAR measured jet suppression, collective flow, R AA suppression. Did it measure a QGP? A detailed study needed to understand the medium created at RHIC Difference in particle-antiparticle production mechanisms? Difference with respect to strange- quark content? What fraction of  ’s are made in jets? A predominant mechanism in p+p and d+Au? Which p T range? Base line for a Au+Au study?

3. Betty BezverkhnyHotQuarks 20043 Data Sets Available: Au+Au Y01 130 GeV Au+Au Y02 200 GeV p+p Y02 200 GeV d+Au Y03 200 GeV p+p Y03 200GeV high p T trigger Au+Au Y04 200 GeV Au+Au Y04 62 GeV Detectors used in the study: TPC & CTB 14M minBias p+p Y02 events available 20M d+Au Y03 events available S olenoidal T racker A t R HIC: 50 institutions from 14 countries – 500+ collaborators! The STAR Experiment

4. Betty BezverkhnyHotQuarks 20044  p+p Procedure: p T >2 1.Apply loose cuts to find  and Anti-  ’s with p T >2 GeV/c in a given event p T >1.5 2.Find primary tracks with p T >1.5 GeV/c in the same event 3.Make sure tracks are not  decay products 4.Calculate  and plot it What we’re up against in p+p: Mean multiplicity of a p+p event: 5.5 Raw  ’s and A-  ’s per event: 3x10 -4 d+Au: higher multipl., better statistics… y  High p T track x  daughters a p -/+ and a  +/-  bachelor, a  ±

5. Betty BezverkhnyHotQuarks 20045 multiplicity p T (GeV/c) STAR Preliminary p+p @ 200 GeV The mean p T appears to increase with multiplicity for for  ’s and K 0 S ( See Mark Heinz’ talk today at 10:45 ). Are  ’s made in higher mult. events? Does it mean  ’s are made in jets? Understanding the data p+p : Mean p T as a function of Multiplicity STAR Preliminary p+p @ 200 GeV Mean ppMinBias event multiplicity: 5.5 5.5 primary tracks/event Further study needed

6. Betty BezverkhnyHotQuarks 20046 Pythia numbers: Pythia numbers: 3.2 x 10 7 events 4.2 x 10 5 (1.3% events) w/a  - 1921  - ’s w/p T >2 GeV/c (0.0016% events) 515 events with at least 1 track w/p T >1.5 GeV and a   w/p T >2GeV/c 705 correlations (1.37 Corr/  - ); |y| < 0.75 3.2x10 7 PYTHIA events p+p  - PYTHIA  - PYTHIA Spectrum is softer: At high p T : significantly fewer   ’s  data dN/dy: 0.00181  data : 0.97 GeV/c p+p : PYTHIA Simulation

7. Betty BezverkhnyHotQuarks 20047 Used both  and Anti-  for the study Used nHits cut to remove same- side split-track correlations, charged tracks are CTB- matched to remove pile-up 13M events, ~770/13M = 0.0052% events with a high p T   or   Not every one of 972 candidate events had a valid primary track STAR Preliminary p+p : Real Data Correlations (data: Y02 ppMinBias) 972 Correlation Candidates: 972 232 Correlated: 232 in 295 correlations (1.3 correlation per candidate) 740 Uncorrelated: 740

8. Betty BezverkhnyHotQuarks 20048 p T distribution: at higher p T statistics start looking similar, however not enough to see a signal. Need to go farther down in p T to gain stats 40M events in Y05 run? Matched  or Anti-  UnMatched  or Anti-  STAR Preliminary p+p = 200 GeV Y02 pTpT pTpT NN s s p+p: What’s Being Correlated?

9. Betty BezverkhnyHotQuarks 20049 No hope in p+p. d+Au? 972 trigger particles

10. Betty BezverkhnyHotQuarks 200410 On to d+Au…  dAu Challenges : underlying event shape, lots more background  dAu Advantages: Lots more statistics background is manageable no thermalized medium expected, thus still a base line  Omegas (not yet!..) ?  All trigger p T are above 2 GeV/c, all associated p T are above 1.5 GeV/c

11. Betty BezverkhnyHotQuarks 200411 11.6M dAu Minimum Bias events considered (more data coming) 6.2M passed all event cuts (triggerID and Z vtx <50 cm) 2477 events with a    or   candidate with p T > 2 GeV d+Au Minimum Bias Y03 0 tracks correlated: 1085 ev 1 track correlated: 772 ev 2+ tracks: 510 ev

12. Betty BezverkhnyHotQuarks 200412 d+Au Correlations Height of the same-side peak is comparable to p+p  -h ± same-side peak height: ~0.4 (  ) vs. ~0.3 (  ) () Height of the same-side peak is comparable to p+p  -h ± same-side peak height: ~0.4 (  ) vs. ~0.3 (  ) (See talk byYing Guo on Saturday) 1392 events with at least 1 correlation 2399 trigger particles 2358 Correlations 1.5 Corr/  !

13. Betty BezverkhnyHotQuarks 200413 Conclusions and Outlook  Good News: There’s hope in d+Au!  In p+p about 25% of observed  ’s above 2GeV seem to be correlated  Might get much more data in Y05…  Not-so-good News: Currently not enough data for a thorough p+p study. Lots more to do!  Need better PYTHIA. Tuning?  Need a thorough d+Au study: Add all available statistics Process the high p T -triggered dataset Measure and subtract the underlying soft physics correlations (momentum conservation)  Need models: how many  ’s come from  resonances? How many should we expect from hard scattering?  March on to Au+Au…

14. Betty BezverkhnyHotQuarks 200414  The end. Thank you, thank you, thank you.

15. Betty BezverkhnyHotQuarks 200415 d+Au Correlations d+Au Correlations : 2 Gaussians fit (  2 /ndf : 1.031/3) Height of the same-side peak is comparable to p+p  -h ± same-side peak height: ~0.4 (  ) vs. ~0.3 (  ) () Height of the same-side peak is comparable to p+p  -h ± same-side peak height: ~0.4 (  ) vs. ~0.3 (  ) (See talk byYing Guo on Saturday) 1392 events with at least 1 correlation 2399 trigger particles 2358 Correlations 1.5 Corr/  !

16. Betty BezverkhnyHotQuarks 200416