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Particle Identified 2-particle correlations

Particle Identified 2-particle correlations. R. Bellwied (WSU) Work done with Ying Guo (WSU), Jana Bielcikova (Yale), Christine Nattrass (Yale) The main goal: Is fragmentation (hadronization) out of medium different than fragmentation out of vacuum ?.

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Particle Identified 2-particle correlations

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  1. Particle Identified 2-particle correlations R. Bellwied (WSU) Work done with Ying Guo (WSU), Jana Bielcikova (Yale), Christine Nattrass (Yale) The main goal: Is fragmentation (hadronization) out of medium different than fragmentation out of vacuum ?

  2. Flavor dependence of fragmentation in vacuum & medium Quark jets vs. gluon jets Leading particle asymmetries Baryon vs. meson asymmetries Particle vs anti-particle asymmetries Clustering

  3. Parton distribution functions(hep-ex/0305109) RHIC

  4. Effects due to softer g-PDF and color factor No evidence for pQCD drop due to q- and g-jets yet.

  5. OPAL flavor results

  6. L-Lbar jet correlations OPAL ALEPH and DELPHI measurements: a.) cos(Q) distribution between correlated pairs distinguishes between isotropic cluster (HERWIG) and non-isotropic string decay (JETSET) for production mechanism. JETSET is clearly favored by the data. b.) strong local correlation of Di-L production based on Dy measurements c.) correlated L-Lbar pairs are produced predominantly within the same jet, i.e. short range compensation of quantum numbers. Question: Are these features of jet correlations modified by the opaque medium ?

  7. Leading Particle Asymmetries Antiparticle to particle ratios in p-p interactions Measured for charmed mesons and strange baryons (E791 – FERMILAB) (hep-ph/0009016) Possible explanation through parton recombination (hep-ph/0301253) Measure enhancement in the production of particles that have one or more valence quarks in common with initial state hadron. Measure associated kaon and hyperon production. Measure particle to antiparticle leading particle behavior.

  8. K0s AKK, hep-ph/0502188 z z pp at RHIC: Hadron formation in QCDNLO for heavy masses requires quark separation in fragmentation function ? In AA: is the fragmentation function modification due to the partonic medium universal ?

  9. pp at RHIC: Hadron formation in QCDNLO for heavy masses requires partonic multiple scattering ?

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

  11. Near side yield as f(centrality)

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

  13. AA/pp ratio for different trigger particle species Rudy Hwa. et al Rudy Hwa. et al • Approaches unity at higher pT and in peripheral collisions

  14.    Alternate (?) or additional (?) explanation: long range  correlations in AA (D. Magestro et al.) d+Au, 40-100% 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 STAR preliminary Au+Au, 0-5% 3 < pT(trig) < 6 GeV2 < pT(assoc) < pT(trig)

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

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

  17. Flavor dependence of 2-particle correlations • 50% Proton/Anti-Proton • 95% π Au+Au 0-5% 1.0<pTAssociated<2.0 • 50%p/pbar • Λ • Λbar • 95% п • K0s Nch/NTrigger • Λ • Anti-Λ • KS0 pTTrigger • Same side associated yield: • Ridge effect (Dh correlation) ? • Coalescence effect ? • Fragmentation effect ? • Need more year-4 stats and bins

  18. Near side yield as f(pt(trig))

  19. Near side yield as f(pt(assoc))

  20. Very different trigger particle species (and multiplicities) give very similar associated particle yields Same side associated particle pt spectra

  21. 8 < pT(trig) < 15 GeV/c Scaling factors relative to d+Au 3 < pT(trig) < 6 GeV/c ~0.54 ~0.25 Near-side yield as a f(z(trig)) An approximation to the fractional momentum carried by the associated particle based on ou measurement: z(trigger) = pT(associated)/pT(trigger)

  22. Summary No strong flavor dependent effects in the two particle correlations in 200 GeV AuAu and CuCu data up to the highest trigger pt of 6 GeV/c. There might be a baryon/meson trend in agreement with Hwa’s recombination We have an interesting way to quantify the trigger bias through z(trig) Plans: 1.) charged trigger and associated V0 correlations 2.) V0-V0 correlations 3.) L-Lbar correlations

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