1. 1 High pt particle spectra and correlations of strange particles in pp, dA, and AA in STAR Rene Bellwied Wayne State University (for M.Heinz, J.Adams, C. Mironov, J.Bielcikova, L.Gaillard, Y.Guo, J.Rumbell, B. Bezhverkhny, R.Witt) STAR Analysis Meeting Purdue University May 16 th -17 th, 2005

2. 2 Talk structure Fragmentation in pp Correlations in pp, dA, AA –Trigger species dependence –Trigger pt dependence –System size dependence Summary

3. 3 Fragmentation in pp Work by M.Heinz, J. Adams, R. Witt, C. Mironov

4. 4 pp at RHIC  NLO breaks down for heavy masses ? p+p->  0 + X

5. 5 NLO variation (W.Vogelsang et al.)

6. 6 PYTHIA studies (M.Heinz) PYTHIA 6.221 + kT = 4 GeV/c + K=3 = broadening or NLO corrections very high

7. 7 How strong are the NLO corrections ? K.Eskola et al. (NPA 713 (2003): Large NLO corrections not unreasonable at RHIC energies. STAR

8. 8 A newer version of PYTHIA v.6.37 includes more initial state multiple scattering

9. 9 Mark’s results (model studies) EPOS (K.Werner): initial state and final state parton cascades (parton ladders), which populate predominantly low pt part of the spectrum. Does well for ALL particle species in pp and dA for STAR, PHENIX and BRAHMS. Spectrum not dominated by fragmentation.

10. 10 New NLO calculation based on STAR data (AKK, hep-ph/0502188) K0s (V0 vs NLO) apparent E inc dependence of separated quark contributions. As of now only tested on light mesons, but also evidence for strange baryons

11. 11 AKK quark separated fragmentation function Conditional probability of valence and non-valence quarks contributing to the FF as a function of fractional momentum z (=x). Needs to be multiplied with partonic production cross section to determine absolute contribution

12. 12 Octet baryon fragmentation Bourrely & Soffer (hep-ph/0305070) Strong heavy quark contribution to parton fragmentation into octet baryons at low fractional momentum in pp !! Quark separation in fragmentation models is important. FFs are not universal. Depend on Q, E inc, and flavor zz

13. 13 Correlations in pp, dA, AA Work by Y. Guo, J. Bielcikova, C. Mironov, J.Rumbell, L. Gaillard, B. Bezhverkhny

14. 14 Λ+h correlations in AuAu and pp 1.5 GeV/c < p T,trig,p T,asso <3.0 GeV/c

15. 15 The associated particle yield is small A few percent compared to the uncorrelated background. Using the proper fit function becomes very important

16. 16 Uncorrelated Background Fitting Method

17. 17 No dependence on centrality or particle species Physics results in AA Centrality dependence: same and back side yield.

18. 18 PHENIX measurement Our data are in agreement with PHENIX

19. 19 Are there differences in associated same side yield as a function of trigger species and pt ?

20. 20 Same side yield for different trigger particle species Indication of different trigger p T dependence for different trigger particle species.. Systematic Errors: Uncorrelated background -- 8~10% Flow – 2.1~2.6% Fitting method – 3% misidentified V0s < 1% trigger bias <1.5%

21. 21 p T (trigger) dependence in d+Au: is there a difference between Λ and Λ ? Within statistical errors the yield/trigger does not depend on type of trigger particle

22. 22 Jana’s study (new AA production, statistics comparable) Old New No more difference between particle & anti-particle

23. 23 Jana’s study (the very latest)

24. 24 What do we learn from system size ? Large AA/pp ratio Same side correlations in AA appear to have larger amplitude and width.

25. 25 Large AA/pp ratio for different trigger particle species Approaches unity at higher pT and in peripheral collisions Apparent description possible through correlated recombination Rudy Hwa. et al

26. 26 R. Hwa et al. predictions based on recombination of thermal and shower partons

27. 27     Alternate (?) explanation: Additional long range  correlations in AA (D. Magestro et al.) In Au+Au, jetlike correlation sits on top of an additional, ~flat correlation in  –  : cannot differentiate between the two correlations –  : additional correlation gets grouped into subtracted background d+Au, 40-100% Au+Au, 0-5% STAR preliminary 3 < p T (trig) < 6 GeV 2 < p T (assoc) < p T (trig)

28. 28  : system size dependence at 200 GeV STAR preliminary Au+Au: peak broadens, height drops with centrality 3 < p T (trig) < 6 GeV 2 < p T (assoc) < p T (trig) |  | < 0.5

29. 29  : p T (trig) dependence of width Broadening in Au+Au compared to p+p, d+Au –Difference grows with decreasing p T (trig) –All systems are consistent for largest p T (trig) bin [6<p T <12 GeV] –Systematic error not assigned (fit range,  projection window) STAR preliminary

30. 30  : p T (trig) dependence of correlated yield Gaussian areas consistent within errors for all p T (trig) –Yield growth with p T (trig): more assoc. particles for higher-p T parton –Correlation yield preserved despite broadening of correlation widths from previous slide STAR preliminary

31. 31 R. Hwa et al. predictions based on recombination of thermal and thermal partons

32. 32 Leon Gaillard’s study (pid  correlations) Needs more statistics What to do with the ridge ? charged-charged Lambda-charged

33. 33 John Rumbell’s study: Associated same side yield in pp, dA, AA 1.0<Pt (assoc) <2.0 2.0<Pt (trigger) <4.0 Circle = Ying AA 200GeV X’s = Jana dA 200GeV Stars = John pp 200 GeV charged-charged K0-charged

34. 34 Very different trigger particle species (and multiplicities) give very similar associated particle yields

35. 35 Same side associated particle pt spectra  In agreement with thermal distribution ??  large AA/pp ratio.  No significant difference between distribution different trigger particle species.

36. 36 Summary Significant NLO contributions in strange particle production in pp. Differences in fragmentation due to non-valence quark contributions ? Associated particle yield not leading particle species dependent in our pt range. Distributions surprisingly similar in multiplicity and kinematics. Large difference in associated particle multiplicity from pp to dA to AA. Can not be explained by fragmentation. Either recombination (thermal-shower) or long range  correlation contribution, which could also be from recombination (thermal-thermal)