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Probing the Medium at RHIC by Identified Particles

Probing the Medium at RHIC by Identified Particles. Olga Barannikova, UIC. HARD. SOFT. p T. 0. 2 GeV/ c. 6 GeV/ c. 10 GeV/ c. Motivation. Particle distributions in transverse momentum What’s hot, what’s not. Pre-RHIC:. Hard / pQCD. Soft / Hydro. Motivation. RHIC. HARD. SOFT.

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Probing the Medium at RHIC by Identified Particles

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  1. Probing the Medium at RHIC by Identified Particles Olga Barannikova, UIC

  2. HARD SOFT pT 0 2 GeV/c 6 GeV/c 10 GeV/c Motivation Particle distributions in transverse momentum What’s hot, what’s not Pre-RHIC: Hard / pQCD Soft / Hydro Quark Matter 2006, Shanghai

  3. Motivation RHIC HARD SOFT pT 0 2 GeV/c 6 GeV/c 10 GeV/c 0 1 2 3 4 5 6 7 8 9 10 pT (GeV/c) Particle distributions in transverse momentum What’s hot, what’s not Hard / pQCD Soft / Hydro Fragmentation +Jet quenching Statistical Models Quark Matter 2006, Shanghai

  4. Motivation RHIC HARD SOFT pT 0 2 GeV/c 6 GeV/c 10 GeV/c L/kos Particle distributions in transverse momentum Intermediate transverse momentum: Properties of the medium and hadronization mechanisms via identified particle measurements Quark Matter 2006, Shanghai

  5. V2 y z x R Rcp ~ RAB cp B/M • PDF  NLO  FF di-hadron STAR, PRL95 (2005) 152301 correlations Intermediate pT Striking features in experimental observations of identified hadrons: Outline: Quark Matter 2006, Shanghai

  6. Quark content determines v2 Simplistic hadronization model : v2q = v2h(pT/n)/n NCQ Scaling for V2 P. Sorensen, QM2005 min. bias (0–80%) 200 GeV Au+Au • PHENIX • Deviation from perfect scaling: • Imperfections of recombination approach? • Wrong scaling variable? • Different hadronization mechanism? Quark Matter 2006, Shanghai

  7. Recombination: beyond the Valence Quarks Simplified approximation: ideal NCO due to recombination of massive valence quarks Gluon degrees of freedom as hidden constituents provide for deviations: v2/n is larger for meson than baryon! B. Müller, R. Fries, S Bass, Phys. Lett. B618, 77-83 (2005) Quark Matter 2006, Shanghai

  8. Pressure gradients converting work into kinetic energy PHENIX, nucl-ex/0608033 Kinetic Energy Scaling What is the scaling variable? • All particles originate from a common flow field • Scaling is observed over extended range of KET Quark Matter 2006, Shanghai

  9. J. Jia1 and C. Zhang, hep-ph/0608187 pT vs. KET Scaling KET/n seems to work better than pT/n with the constituent quark scaling STAR • How is this observation accommodated the recombination approach? Quark Matter 2006, Shanghai

  10. Scaling in Transport Models • Is the NCO scaling a unique feature of the recombination/coalescence models? Y. Lu et al., JoP. G 32 1121 (2006) Hadron-string transport models reproduce the NCQ scaling qualitatively (The absolute values remain problematic) Quark Matter 2006, Shanghai

  11. STAR: Nucl. Phys. A 757 (2005) 102 Two groups (2<pT<6GeV/c):, Ks, K, K*, φmesons p, Λ, Ξ, Ω baryons 0-10%/60-80% p p 0-10%/60-80% 0-10%/60-92% 2 4 6 8 10 2 4 6 8 10 2 4 6 8 10 Rcp Scaling Quark Matter 2006, Shanghai

  12. Fries, Muller, Nonaka, Bass Hwa, Yang Recombination + Fragmentation is needed to reproduce identified spectra and Rcp measurements at higher pT. Rcp from Recombination • Rcp splitting between baryons and mesons comes naturally in the recombination approach R.J. Fries, et al., Phys. Rev. Lett. 90 202303 (2003). R. C. Hwa, et al., Phys. Rev. C 70, 024905 (2004). V. Greco, et al., Phys. Rev. C 68, 034904(2003). Quark Matter 2006, Shanghai

  13. p K Hydro+Jet T.Hirano, Y.Nara, Phys.Rev.C69,034908(2004) Intermediate pT: “Hard” pions vs. “Soft” protons Between Soft and Hard Crossover: 1.8 GeV/c , 2.6 GeV/c K, 3.8 GeV/c p I. Vitev and M. Gyulassy, Phys. Rev. C 65, 041902 (2002) S. J. Casalderrey and E. V. Shuryak, hep-ph/0305160 …….. Quark Matter 2006, Shanghai

  14. L/K0s STAR STAR pT (GeV/c) _ p/π PHENIX D. Morrison Baryon-meson Anomaly M. Lamont L. Ruan PHENIX, Phys. Rev. C 69, 024904 (2004) STAR, Phys. Rev. Lett. 97 (2006) 152301 Higher relative baryon yields (ISR: p/π ~ 0.2) Enhancement observed across all measured species: p/p, L/K, / All RHIC energies and ions Quark Matter 2006, Shanghai

  15. Greco, et al. Vitev,Gyulassy Fries, et al. L/K0 p/π Peitzmann Hwa,et al. • PHENIX • STAR Baryon Enhancement • Soft + Hard: “Recombination” or “Interplay”? Soft+Quench I. Vitev, M. Gyulassy, Nucl. Phys. A715, 779 (2003) Hydro+pQCD T. Peitzmann, Nucl. Phys. A727, 179(2003) STAR Coalescence V. Greco, et al. Phys. Rev. Lett. 90, 202302 (2003) Recombination R.J. Fries, et al., Phys. Rev. C 68, 044902 (2003) R.C. Hwa and C.B. Yang, Phys. Rev. C 67, 034902 (2003) • How to distinguish hadronization mechanisms? Quark Matter 2006, Shanghai

  16. The Jet Factor S. Blyth, this Quark Matter Details of Soft/Hard cocktail are extremely significant! • Problems for pQCD sector: • Large baryon/meson ratio • Significant v2 (from jet quenching?) Similar E-loss for q- and g-jets • Could it be “soft-hard” recombination? Look in the jets! In ReCo composition is different for different particle species Quark Matter 2006, Shanghai

  17. 1.0 < pT<1.3 GeV/c 1.0 < pT<1.3 GeV/c 2-particle Correlations Baryons and mesons both have jet-like partner particles W. Holzmann, WWND 2006 • h-trigger: • baryon production is enhanced, particularly on away side • Baryon vs. meson triggers: • lower associated jet yield Associate: baryon/meson • Recombination models: • Modified correlation is expected (SSTS) • Quantitative predictions for •  , p,, K ratios and hadron correlations at high pT J. Bielcikova, HP 2006 Trigger: baryon/meson

  18. Two outstanding issues: • Long range η correlations are not accounted for • Baryon enhancement in the ridge J. Bielcikova, this Quark Matter • Multi-strange hadron correlations pTAssoc. (GeV/c) Correlations in Recombination Near-side Yields Ratio • ReCo Qualitative agreement with Recombination predictions R. Hwa, Z. Tan: nucl-th/0503060 Quark Matter 2006, Shanghai

  19. Summary • A great variety of new experimental results on identified hadrons • The small subset of those presented in this talk was focused on striking features of identified measurements: • Hadronization and/or jet-medium interactions result in baryon enhancement, baryon-meson splitting in the intermediate pT sector, complex systematic at high pT • Elliptic flow is experienced by all hadrons (including strange and multi-strange), hydro-like at low-pT, NCO scaling at intermediate pT • Di-hadron correlationsshow jet structures for all hadrons studied, with indications of jet-induced baryon enhancements • Mechanisms of jet-medium interactions and hadronization are the keys to the understanding of the matter created PID measurements hold those keys! Quark Matter 2006, Shanghai

  20. Backup Quark Matter 2006, Shanghai

  21. Baryon enhancement in soft ridge h p p pTassoc > 2 GeV/c Au+Au 0-10% STAR Baryon enhancement in g-jets: pT trig GeV/c H. Liu and Zh. Xu, nucl-ex/0610035 Jet-induced Baryon Enhancement • New physics? J. Putschke, HQ 2006 Au+Au central “Jet” “Ridge” 3<pTtrig<4 GeV/c, pTassoc>2 GeV/c • Rich structure in Au+Au data: • Suppression of the Away-side yield • Broadening/”ridge” on the Near-side

  22. Pbar/p ratio: model X.N. Wang: PRC58(2321)1998. PID spectra, centrality dependence of pbar/p and pbar/ ratios, address the color charge dependence of energy lossTo further understand how the gluon jet/quark jet interact with the medium created in Au+Au. collisions. Quark Matter 2006, Shanghai

  23. Pbar/p ratio: data STAR Preliminary -/+ are consistent with flat at unity in all pT, no significant centrality dependence. pbar/p ratio: no significant centrality dependence, not consistent with the jet quenching prediction (X.N. Wang, PRC 58 (2321) 1998). Quark Matter 2006, Shanghai

  24. Energy Loss: q vs. g • In the NLO calculation that best describes p+p data, significant difference in the gluon contribution between proton and pion spectra • Yet, no significant difference in suppression: no difference between gluon and quark energy loss? Quark Matter 2006, Shanghai

  25. Sensitive to early evolution PRC (72), 014904 (2005) • Quark content determines v2 Simplistic hadronization model : v2q = v2h(pT/n)/n Above pT ~2 GeV/c two groups of hadrons: , K0s, K, p, Λ, ,  Origin of Flow Why elliptic flow? • Mass ordering at low pT: • hydro with early thermalization • (Multi-)strange hadron v2 hints the partonic origin of collectivity Quark Matter 2006, Shanghai

  26. V2 at High pT High –pt : Density & geometry-driven absorption anisotropy Quark Matter 2006, Shanghai

  27. PHENIX PID Correlations W. Holzmann WWND 2006 • Away side baryon/meson ratio ~2x larger than on near side • Centrality dependent trend of baryon/meson ratio observed • Qualitatively similar to ratio of singles distribution from PHENIX. • Particle species dependent jet modification Quark Matter 2006, Shanghai

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