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Olga Barannikova, UIC Probing the Medium at RHIC by Identified Particles
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Olga BarannikovaQuark Matter 2006, Shanghai2 Particle distributions in transverse momentum What’s hot, what’s not pTpT 2 GeV/c 10 GeV/c 0 6 GeV/c Hard / pQCD Soft / Hydro Pre-RHIC: Motivation
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Olga BarannikovaQuark Matter 2006, Shanghai Particle distributions in transverse momentum What’s hot, what’s not Statistical Models Fragmentation +Jet quenching 0 1 2 3 4 5 6 7 8 9 10 p T (GeV/c) Motivation Soft / Hydro Hard / pQCD pTpT 2 GeV/c 10 GeV/c 0 6 GeV/c
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Olga BarannikovaQuark Matter 2006, Shanghai /k o s Particle distributions in transverse momentum Intermediate transverse momentum: Motivation pTpT 2 GeV/c 10 GeV/c 0 6 GeV/c Properties of the medium and hadronization mechanisms via identified particle measurements
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Olga BarannikovaQuark Matter 2006, Shanghai5 Intermediate p T Striking features in experimental observations of identified hadrons: Outline: x z y PDF NLO FF R cp ~ R AB STAR, PRL95 (2005) 152301
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Olga BarannikovaQuark Matter 2006, Shanghai6 Quark content determines v 2 Simplistic hadronization model : v 2 q = v 2 h (p T / n )/ n 200 GeV Au+Au min. bias (0 – 80%) NCQ Scaling for V2 Deviation from perfect scaling: Imperfections of recombination approach? Wrong scaling variable? Different hadronization mechanism? P. Sorensen, QM2005 PHENIX o PHENIX
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Olga BarannikovaQuark Matter 2006, Shanghai7 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: v 2 /n is larger for meson than baryon! B. Müller, R. Fries, S Bass, Phys. Lett. B618, 77-83 (2005)
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Olga BarannikovaQuark Matter 2006, Shanghai8 All particles originate from a common flow field Scaling is observed over extended range of KE T Kinetic Energy Scaling Pressure gradients converting work into kinetic energy PHENIX, nucl-ex/0608033 What is the scaling variable?
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Olga BarannikovaQuark Matter 2006, Shanghai9 p T vs. KE T Scaling STAR How is this observation accommodated the recombination approach? KE T /n seems to work better than p T /n with the constituent quark scaling J. Jia1 and C. Zhang, hep-ph/0608187
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Olga BarannikovaQuark Matter 2006, Shanghai10 Scaling in Transport Models Hadron-string transport models reproduce the NCQ scaling qualitatively ( The absolute values remain problematic) Is the NCO scaling a unique feature of the recombination/coalescence models? Y. Lu et al., JoP. G 32 1121 (2006)
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Olga BarannikovaQuark Matter 2006, Shanghai11 R cp Scaling 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 0-10%/60-80% 0-10%/60-92% 2 4 6 8 10
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Olga BarannikovaQuark Matter 2006, Shanghai12 R cp from Recombination Rcp splitting between baryons and mesons comes naturally in the recombination approach Hwa, Yang Recombination + Fragmentation is needed to reproduce identified spectra and Rcp measurements at higher p T. Fries, Muller, Nonaka, Bass 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).
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Olga BarannikovaQuark Matter 2006, Shanghai13 Intermediate p T : “Hard” pions vs. “Soft” protons K p Between Soft and Hard Crossover: 1.8 GeV/c , 2.6 GeV/c K, 3.8 GeV/c p T.Hirano, Y.Nara, Phys.Rev.C69,034908(2004) Hydro+Jet I. Vitev and M. Gyulassy, Phys. Rev. C 65, 041902 (2002) S. J. Casalderrey and E. V. Shuryak, hep-ph/0305160 ……..
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Olga BarannikovaQuark Matter 2006, Shanghai14 STAR /K 0 s p T (GeV/c) STAR Baryon-meson Anomaly Higher relative baryon yields (ISR: p/π ~ 0.2) Enhancement observed across all measured species: p/ , /K, All RHIC energies and ions M. Lamont L. Ruan PHENIX, Phys. Rev. C 69, 024904 (2004) STAR, Phys. Rev. Lett. 97 (2006) 152301 PHENIX D. Morrison _ p/π
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Olga BarannikovaQuark Matter 2006, Shanghai15 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) Fries, et al. Greco, et al. Vitev, Gyulassy Hwa, et al. Peitzmann p/π PHENIX STAR 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?
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Olga BarannikovaQuark Matter 2006, Shanghai16 The Jet Factor S. Blyth, this Quark Matter Problems for pQCD sector: Large baryon/meson ratio Significant v 2 (from jet quenching?) Similar E-loss for q- and g-jets In ReCo composition is different for different particle species Could it be “soft-hard” recombination? Look in the jets! Details of Soft/Hard cocktail are extremely significant!
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17 1.0 < p T <1.3 GeV/c 2-particle Correlations Baryons and mesons both have jet-like partner particles Trigger: baryon/meson h-trigger: baryon production is enhanced, particularly on away side Baryon vs. meson triggers: lower associated jet yield Recombination models: Modified correlation is expected (SS TS) Quantitative predictions for , p, , K ratios and hadron correlations at high p T Associate: baryon/meson 1.0 < p T <1.3 GeV/c J. Bielcikova, HP 2006 W. Holzmann, WWND 2006
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Olga BarannikovaQuark Matter 2006, Shanghai18 Correlations in Recombination p T Assoc. (GeV/c) Near-side Yields Ratio R. Hwa, Z. Tan: nucl-th/0503060 ─ ReCo J. Bielcikova, this Quark Matter Two outstanding issues: 2.Multi-strange hadron correlations 1.Long range η correlations are not accounted for Baryon enhancement in the ridge Qualitative agreement with Recombination predictions
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Olga BarannikovaQuark Matter 2006, Shanghai19 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 p T sector, complex systematic at high p T Elliptic flow is experienced by all hadrons (including strange and multi- strange), hydro-like at low-p T, NCO scaling at intermediate p T Di-hadron correlations show 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!
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Olga BarannikovaQuark Matter 2006, Shanghai20 Backup
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Olga Barannikova21 Jet-induced Baryon Enhancement Rich structure in Au+Au data: Suppression of the Away-side yield Broadening/”ridge” on the Near-side J. Putschke, HQ 2006 3 2 GeV/c “Ridge” Au+Au central “Jet” p T assoc > 2 GeV/c Au+Au 0-10% STAR p T trig GeV/c hphp Baryon enhancement in soft ridge Baryon enhancement in g-jets: H. Liu and Zh. Xu, nucl-ex/0610035 New physics?
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Olga BarannikovaQuark Matter 2006, Shanghai22 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.
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Olga BarannikovaQuark Matter 2006, Shanghai23 Pbar/p ratio: data 1. - / + are consistent with flat at unity in all p T, no significant centrality dependence. 2. pbar/p ratio: no significant centrality dependence, not consistent with the jet quenching prediction ( X.N. Wang, PRC 58 (2321) 1998). STAR Preliminary
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Olga BarannikovaQuark Matter 2006, Shanghai24 –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? Energy Loss: q vs. g
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Olga BarannikovaQuark Matter 2006, Shanghai25 Why elliptic flow? Origin of Flow Mass ordering at low p T : hydro with early thermalization (Multi-)strange hadron v 2 hints the partonic origin of collectivity Quark content determines v 2 Simplistic hadronization model : v 2 q = v 2 h (p T / n )/ n PRC (72), 014904 (2005) Above p T ~2 GeV/c two groups of hadrons: , K 0 s, K , p, Λ, , Sensitive to early evolution
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Olga BarannikovaQuark Matter 2006, Shanghai26 V2 at High p T High –pt : Density & geometry-driven absorption anisotropy
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Olga BarannikovaQuark Matter 2006, Shanghai27 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
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