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Status and Implications of PID measurements at high pT Olga Evdokimov University of Illinois at Chicago
Outline • The motivation: • Where we are: current picture • High pT – What? Where? Why? • Identified particles at high pT: • The identified particle measurements • Implications and Theoretical input • Open questions • Summary 2 Olga Evdokimov University of Illinois at Chicago
leading particle hadrons q q hadrons leading particle Medium properties via jets • Jet Tomography: calibrated (?) probes • Described by pQCD • Particle production in hard sector • convolution of PDF NLO FF • Energy loss mechanisms: • need discriminative measurements • Path length effects non-trivial: • need discriminative measurements • Flavor/color-charge dependence of parton-medium coupling • In-medium fragmentation/ hadronization • ….. High pT PID 3 Olga Evdokimov University of Illinois at Chicago
CDF Collaboration, PRD 65, 072005, 2002. Define “high” In pp: inclusive cross-section is dominated by jet production above ~4 GeV/c What about RHIC matter? • Quick look at intermediate pT: • “Lingering” hydro flow • Baryon anomaly • Ridge T.Hirano, Y.Nara, PRC69,034908(2004) High: pT > 6 Gev/c 4 Olga Evdokimov University of Illinois at Chicago
Jet quenching at RHIC PHENIX p0 @ 200 GeV Nuclear Modification Factors • Jet quenching evident in strong suppression of high pT hadrons • Multiple models provide a successful descriptions of the suppression levels • Most include radiative and collisional energy loss coll rad rad+coll Fits: G. Qin et al, PRL100:072301, 2008 5 Olga Evdokimov University of Illinois at Chicago
Jet quenching: Data & Models S. Bass et al, arXiv:0808.0908 TECHQM Collaboration: Set to compare jet-quenching scenarios with the same constraints: • same nuclear profile • same structure & fragmentation functions • same medium (hydro) • RAA of p(h) is not very discriminating • Need more differential measurements H. Caines CATHIE/TECHQM-2009 * Similar results from GLV and WHDG 6 Olga Evdokimov University of Illinois at Chicago
Medium properties and E-loss S. Wicks et al - NPA784:426-442,2007 The real Outline: • Identified particles spectra in pp and AA • High-pT ratios and Nuclear modification factors Mass, Color-charge, Flavor effects • Heavy flavor studies • Correlations with identified particles S. Albino, et ak - NPB 725 (2005) 181 7 Olga Evdokimov University of Illinois at Chicago
F. Simon p+p→p0+X p+p→p0+X hadrons leading particle S.S. Adler et al, PRL 91 241803 q q hadrons leading particle The reference: p and p Simon, private communication KKP: B. Kniehl, G. Kramer, P¨otter, Nucl. Phys. B597, 337 (2001) AKK: S. Albino, B Kniehl, G. Kramer, arXiv: 0803.2768v2 DSS: D. de Florian, W. Vogelsang, F. Wagner, arXiv: 0708.3060v3 8 Olga Evdokimov University of Illinois at Chicago
STAR preliminary STAR preliminary The reference: kaons Y. Xu SQM09 • Consistent results for K0S and K • Extended kaon spectra – new constrains for FF • Direct measurements of FF: Pythia works wellfor K0S , not so well for L A. Timmins SQM09 STAR preliminary 9 Olga Evdokimov University of Illinois at Chicago
Sample of RAA in PHENIX C. Vale, Quark Matter 09 10 Olga Evdokimov University of Illinois at Chicago
PRELIMINARY arXiv: 0804.4760 PHENIX QM09: “At high pT RCP(p) approaches RCP(p)” STAR preliminary Zooming in: p and p • The issue: pQCD predicts E-loss dependence on color-charge factors CA/CF = 9/4 • Is there issue? @10 GeV/c: p(0.60q+0.40g), p (0.05q+0.95g) STAR QM08: High pT RAA(p)>RAA(p) 11 Olga Evdokimov University of Illinois at Chicago
Jet chemistrymodifications pQCD expectation :RAA(p) < RAA() • Observation from central Au+Au collisions: RAA(r)~RAA() <RAA(K)<RAA(p)K/ (AA)>K/ (pp) • Hierarchy consistent with jet flavor conversion parton medium interactions STAR Preliminary p k π W. Liu and R. Fries, PRC 77, 054902 (2008) 12 Olga Evdokimov University of Illinois at Chicago
Medium-induced modifications • HT contributions • - direct hadron production • _ • q q p q q g • Flavor-conversions • S. Brodsky, A. Sickles, PLB668 111 (2008) • Leads to RAA() <RAA(p) • Describes decreasing trend pT for v2 for (anti)protons • Centrality dependence of proton-triggered correlations W. Liu and R. Fries, PRC 77, 054902 (2008) d • Reverses expected trend /p− ratio from pp to Au+Au to • Boosts Kaon production ~ factor 2 due to abundance of QGP s-quarks • Reverses expected trend /p− ratio from pp to Au+Au to • Boosts Kaon production ~ factor 2 due to abundance of QGP s-quarks 13 Olga Evdokimov University of Illinois at Chicago
Energy loss for Heavy Flavor • Heavy quarks – calculable (?) probes for medium properties • Discriminating power for energy loss scenarios • Open heavy flavor • Smaller gluon bremsstrahlung for heavy quarks • Smaller suppression at high pT • Light flavor energy loss • Strong suppression at high pT in RAA • Radiative vs. collisional energy loss 14 Olga Evdokimov University of Illinois at Chicago
STAR PRL, 98, 192301 (2007) High pT suppression for HF RAA for non-photonic electrons (from heavy flavor decays) PHENIX QM09 No decrease in suppression for non-photonic e 15 Olga Evdokimov University of Illinois at Chicago
Energy loss for beauty • Heavy Flavor results from non-photonic electrons: • Strong suppression of heavy-flavor at high pT in RAA ~ light mesons • Inconsistent with radiative energy loss prediction needs collisional too • What about beauty? e –D0 correlation using like-sign e-K pairs Mid-rapidity e + forward m • Agreement on b- and c- fractions from multiple STAR & PHENIX studies • b-decays contribution to non-photonic electrons: ~50% at pT~5 GeV/c • strong suppression in AA for both charm and beauty! mostly B ~25%B,75%C 16 Olga Evdokimov University of Illinois at Chicago
Summary & Outlook • RHIC: Systematic studies of the partonic medium • Systematic studies of identified particle spectra • New constrains of FF • Jet-chemistry modifications in AA • Jet flavor conversion / direct hadron production / ?? • Ongoing challenges • Color-charge effects and jet chemistry • High pT suppression: both Charm and Beauty? • ………… 17 Olga Evdokimov University of Illinois at Chicago