Multi-strange Baryon Correlations in p+p and d+Au Collisions at √ s NN = 200 GeV

1. Betty Bezverkhny Yale University For the Collaboration Hot Quarks ’04, Taos, New Mexico Multi-strange Baryon Correlationsin p+pandd+Au Collisions at √sNN = 200 GeV

2. Previously published: Ncharged correlations in p+p Adler et al., PRL90:082302 (2003), STAR trigger Why Study Identified Correlations? STAR measured jet suppression, collective flow, RAA 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 ofX’s are made in jets? A predominant mechanism in p+p and d+Au? Which pT range? • Base line for a Au+Au study? HotQuarks 2004

3. 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 pT 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 The STAR Experiment Solenoidal Tracker At RHIC: 50 institutions from 14 countries – 500+ collaborators! HotQuarks 2004

4. Procedure: • Apply loose cuts to find X and Anti-X’s with pT >2 GeV/c in a given event • Find primary tracks withpT>1.5GeV/cin the same event • Make sure tracks are not X decay products • Calculate Df and plot it • What we’re up against in p+p: • Mean multiplicity of a p+p event: 5.5 • Raw X’s and A-X’s per event: 3x10-4 • d+Au: higher multipl., better statistics… y High pT track X x Df X bachelor, a p± X daughters a p-/+and a p +/- p+p HotQuarks 2004

5. multiplicity STAR Preliminary p+p @ 200 GeV pT (GeV/c) STAR Preliminary p+p @ 200 GeV Understanding the data p+p : Mean pT as a function of Multiplicity The mean pT appears to increase with multiplicity for for L’s and K0S (See Mark Heinz’ talk today at 10:45). Are X’s made in higher mult. events? Does it mean X’s are made in jets? Mean ppMinBias event multiplicity: 5.5 primary tracks/event Further study needed HotQuarks 2004

6. PYTHIA Spectrum is softer: At high pT: significantly fewer X-’s p+p X- PYTHIA X- 3.2x107 PYTHIA events X data dN/dy: 0.00181 X data <pT>: 0.97 GeV/c p+p: PYTHIA Simulation Pythia numbers: • 3.2 x 107 events • 4.2 x 105 (1.3% events) w/a X- • 1921 X-’s w/pT>2 GeV/c (0.0016% events) • 515 events with at least 1 track w/pT >1.5 GeV and a X- w/pT>2GeV/c • 705 correlations (1.37 Corr/X-); • |y| < 0.75 HotQuarks 2004

7. STAR Preliminary p+p: Real Data Correlations (data: Y02 ppMinBias) • Used both X and Anti-X 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 pTX- orX+ • Not every one of 972 candidate events had a valid primary track • Correlation Candidates: 972 • Correlated: 232 in 295 correlations (1.3 correlation per candidate) • Uncorrelated: 740 HotQuarks 2004

8. MatchedXorAnti-X STAR Preliminary p+p = 200 GeV Y02 pT UnMatched Xor Anti-X STAR Preliminary p+p = 200 GeV Y02 pT s s NN NN p+p: What’s Being Correlated? • pT distribution: • at higher pT statistics start looking similar, however not enough to see a signal. Need to go farther down in pT to gain stats • 40M events in Y05 run? HotQuarks 2004

9. 972 trigger particles No hope in p+p. d+Au? HotQuarks 2004

10. 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 triggerpT are above 2 GeV/c, all associatedpT are above 1.5 GeV/c HotQuarks 2004

11. d+Au Minimum Bias Y03 0 tracks correlated: 1085 ev 1 track correlated: 772 ev 2+ tracks: 510 ev • 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 X-or X+ candidate with pT > 2 GeV HotQuarks 2004

12. d+Au Correlations • 1392 events with at least 1 correlation • 2399 trigger particles • 2358 Correlations • 1.5 Corr/X ! Height of the same-side peak is comparable to p+p L-h± same-side peak height: ~0.4 (X) vs. ~0.3 (L) (See talk byYing Guo on Saturday) HotQuarks 2004

13. Conclusions and Outlook • Good News: There’s hope in d+Au! • In p+p about 25% of observed X’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 pT-triggered dataset • Measure and subtract the underlying soft physics correlations (momentum conservation) • Need models: how many X’s come from X resonances? How many should we expect from hard scattering? • March on to Au+Au… HotQuarks 2004

14. The end. Thank you, thank you, thank you. HotQuarks 2004

15. d+Au Correlations: 2 Gaussians fit (c2/ndf : 1.031/3) • 1392 events with at least 1 correlation • 2399 trigger particles • 2358 Correlations • 1.5 Corr/X ! Height of the same-side peak is comparable to p+p L-h± same-side peak height: ~0.4 (X) vs. ~0.3 (L) (See talk byYing Guo on Saturday) HotQuarks 2004

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