Hot Quarks 04 Taos New Mexico Multistrange Baryon

Hot Quarks ’ 04, Taos, New Mexico Multi-strange Baryon Correlations in p+p and d+Au Collisions at √s. NN = 200 Ge. V Betty Bezverkhny Yale University For the Betty Bezverkhny Hot. Quarks 2004 Collaboration

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 Previously published: Ncharged correlations in p+p Adler et al. , PRL 90: 082302 (2003), STAR Difference in particle-antiparticle production mechanisms? • • Difference with respect to strangequark content? • What fraction of X’s are made in jets? A predominant mechanism in p+p and d+Au? Which p. T range? trigger Betty Bezverkhny • Base line for a Au+Au study? Hot. Quarks 2004 2

Data Sets Available: • Au+Au Y 01 130 Ge. V • Au+Au Y 02 200 Ge. V • p+p Y 02 200 Ge. V • d+Au Y 03 200 Ge. V • p+p Y 03 200 Ge. V high p. T trigger • Au+Au Y 04 200 Ge. V • Au+Au Y 04 62 Ge. V The STAR Experiment • Detectors used in the study: TPC & CTB • 14 M min. Bias p+p Y 02 events available • 20 M d+Au Y 03 events available Solenoidal Tracker At RHIC: Betty Bezverkhny Hot. Quarks 2004 50 institutions from 14 countries – 500+ collaborators! 3

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: 3 x 10 -4 • d+Au: higher multipl. , better statistics… Procedure: 1. Apply loose cuts to find X and Anti-X’s with p. T >2 Ge. V/c in a given event 2. Find primary tracks with p. T>1. 5 Ge. V/c in the same event 3. Make sure tracks are not X decay products 4. Calculate Df and plot it y High p. T track X x Df X bachelor, a p± p+p Betty Bezverkhny X daughters a p-/+ and a p +/- Hot. Quarks 2004 4

Understanding the data p+p : Mean p. T as a function of Multiplicity The mean p. T appears to increase with multiplicity for L’s and K 0 S (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 pp. Min. Bias event multiplicity: 5. 5 primary tracks/event STAR Preliminary p+p @ 200 Ge. V multiplicity STAR Preliminary p+p @ 200 Ge. V d e d y d tu s r e e n tr he Fu p. T (Ge. V/c) Betty Bezverkhny Hot. Quarks 2004 5

p+p: PYTHIA Simulation PYTHIA Spectrum is softer: At high p. T: significantly fewer X -’s p+p X- Pythia numbers: • • • PYTHIA X- 3. 2 x 107 events 4. 2 x 105 (1. 3% events) w/a X 1921 X-’s w/p. T>2 Ge. V/c (0. 0016% events) 515 events with at least 1 track w/p. T >1. 5 Ge. V and a Xw/p. T>2 Ge. V/c 705 correlations (1. 37 Corr/X-); |y| < 0. 75 Betty Bezverkhny 3. 2 x 107 PYTHIA events Hot. Quarks 2004 X data d. N/dy: 0. 00181 X data <p. T>: 0. 97 Ge. V/c 6

p+p: Real Data Correlations (data: Y 02 pp. Min. Bias) • Used both X and Anti-X for the study • Used n. Hits cut to remove sameside split-track correlations, charged tracks are CTB-matched to remove pile-up • 13 M events, ~770/13 M = 0. 0052% events with a high p. T X- or X+ • Not every one of 972 candidate events had a valid primary track Correlation Candidates: STAR Preliminary Betty Bezverkhny 972 Hot. Quarks 2004 7

p+p: What’s Being Correlated? Matched X or Anti-X p. T distribution: STAR Preliminary p+p s. NN = 200 Ge. V Y 02 p. T Un. Matched X or Anti-X STAR Preliminary p+p s. NN = 200 Ge. V Y 02 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 40 M events in Y 05 run? p. T Betty Bezverkhny Hot. Quarks 2004 8

972 trigger particles . p p+ n i e ? p o Au h + o d N Betty Bezverkhny Hot. Quarks 2004 9

On to d+Au… ù d. Au Challenges : • underlying event shape, • lots more background ù d. Au Advantages: • Lots more statistics • background is manageable • no thermalized medium expected, thus still a base line ù Omegas (not yet!. . ) ? ù All trigger p. T are above 2 Ge. V/c, all associated p. T are above 1. 5 Ge. V/c Betty Bezverkhny Hot. Quarks 2004 10

1 track correlated: 772 ev 0 tracks correlated: 1085 ev d+Au Minimum Bias Y 03 2+ tracks: 510 ev • 11. 6 M d. Au Minimum Bias events considered (more data coming) • 6. 2 M passed all event cuts (trigger. ID and Z vtx <50 cm) • 2477 events with a X- or X+ candidate with p. T > 2 Ge. V Betty Bezverkhny Hot. Quarks 2004 11

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 by. Ying Guo on Saturday) ( Betty Bezverkhny Hot. Quarks 2004 12

Conclusions and Outlook ù Good News: There’s hope in d+Au! ù In p+p about 25% of observed X’s above 2 Ge. V seem to be correlated ù Might get much more data in Y 05… ù Not-so-good News: Currently not enough data for a thorough p+p study. Lots more to do! ù Need better PYTHIA. Tuning? ù 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) ù Need models: how many X’s come from X resonances? How many should we expect from hard scattering? ù March on to Au+Au… Betty Bezverkhny Hot. Quarks 2004 13

ù The end. Thank you, thank you. Betty Bezverkhny Hot. Quarks 2004 14

d+Au Correlations: 2 Gaussians fit (c 2/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 by. Ying Guo on Saturday) ( Betty Bezverkhny Hot. Quarks 2004 15

Betty Bezverkhny Hot. Quarks 2004 16