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Identified Hadron Production at low to mid p T (~5.0GeV/c) in Au+Au and Cu+Cu Collisions Maya SHIMOMURA University of Tsukuba 2007 年 2 月 10,11 日 heavy ion café 松本合宿
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Contents Introduction –Baryon Anomaly at RHIC Recent results –Spectra measurements –p/pi ratio for various systems –proton R AA –(models) Summary
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Introduction
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Baryon Anomaly ( Baryon Enhancement ) at RHIC PHENIX: PRL 91, 172301 (2003), PRC 69, 034909 (2004), PRC 74, 024904 (2006) R CP (or R AA ) Pions: pT> 2 GeV/c の領域に強い suppression がみられる (jet quenching effect) Protons: p T =2-5 GeV/c の領域で Rcp= ~ 1 になっている
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Anomalous Composition R cp – メソンとバリオンで違う曲線を描いている メソンが、他のメソンと同じ振る 舞いをすることから、 mass の違いに よるものではないといえる p/ and p/ ratios – p T=2~5GeV/c では p/ が p/ に比べて 大きい –Centrality による違いがはっきりみえる –d+Au, p+p, Au+Au の peripheral は、同じ振 る舞いをする。
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results
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Many spectra measurements are done. Phenix preliminary More and more … Au+Au/Cu+Cu/p+p, 22.5/62.4/200 GeV, pi(±,0) and (anti-)proton.
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Compilation of p/ ratios (central) Cu+Cu 22.5 GeV, p/ ratio in central agree with p+p. Many protons, mostly from participant nucleons. * No weak decay feed-down correction applied.
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Compilation of p/ ratios (central) Cu+Cu 62.4 GeV, p/ ratio larger than those in p+p and Cu+Cu 22.5 GeV. * No weak decay feed-down correction applied.
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Compilation of p/ ratios (central) Cu+Cu 200 GeV, similar to those in Cu+Cu 62.4 GeV. * No weak decay feed-down correction applied.
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Compilation of p/ ratios (central) Au+Au 62 GeV, p/ - is unchanged, p/ + getting larger. * No weak decay feed-down correction applied. Au+Au collision の結果を加えると・・・
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Compilation of p/ ratios (central) Au+Au 200 GeV, p/ - is enhanced, p/ + is similar to p/ - * No weak decay feed-down correction applied.
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Compilation of p/ ratios (peripheral) Conversing to the same line for both p/ - and p/ + * No weak decay feed-down correction applied.
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Centrality dep. of p/ in Au+Au 200 GeV p/ in Au+Au 200 GeV - p/ (pbar/ ) ratios seem to turn over at intermediate p T, and be close to the value of fragmentation at higher p T. - Clear peak in central events than that in peripheral. - Indicating a transition from soft to hard at intermediate p T.
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- Baryon enhancement observed in Cu+Cu at 200 GeV. - p T dependence in Cu+Cu is similar to that in Au+Au. Centrality dep. of p/ in Cu+Cu 200 GeV Phenix preliminary p/ in Cu+Cu 200 GeV
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Centrality dep. of p/ in Cu+Cu 22.5 GeV More protons transported to mid rap. instead of production for Cu+Cu 22GeV. Almost no centrality dependence in p/ . p/ - ratios are ~0.3-0.4 at p T = 2 GeV/c, which is close to the value in p+p. * No weak decay feed-down correction applied.
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p/ + ratios are reduced, compared to those in Cu+Cu 22 GeV. p/ - ratio in central collisions reaches R=~0.6 at p T = 2 GeV/c. Centrality dependence is also seen. Centrality dep. of p/ in Cu+Cu 62.4 GeV * No weak decay feed-down correction applied.
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s NN dep. of p/ - and p/ + ratio (central) Increasing as a function of s. p-bar/ - と p/ + では、 逆の傾向をしめしている。 decreasing as a function of s.
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p/ vs. N part 1/3 Phenix preliminary Cu+Cu 200 GeV vs. Au+Au 200 GeV NOTE: No weak decay feed-down correction applied. TOF (<3 GeV/c) ACC (>3 GeV/c) 0.6 - 1.5 GeV/c1.0 - 2.0 GeV/c2.0 - 3.0 GeV/c3.0 - 4.0 GeV/c4.0 - 5.0 GeV/c pTpT pTpT Phenix preliminary - Centrality dependence in Cu+Cu looks similar to that in Au+Au (N part scaling at same sqrt(s NN )!). - Even though overlap region has a different geometrical shape. - Slight difference in the magnitude seen.
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R AA vs. p T - Proton, antiproton are enhanced at 1.5 - 4 GeV/c for all centralities. (enhancement > suppression) - Suppression is seen for pions, kaons. NOTE: No weak decay feed-down correction applied. Phenix preliminary
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R AA vs. p T - Proton, antiproton are enhanced at 1.5 - 4 GeV/c for all centralities. (enhancement > suppression) - Suppression is seen for pions, kaons. NOTE: No weak decay feed-down correction applied. Phenix preliminary NOTE: Systematic errors (~10%) for overall normalization not shown. - Similar N part dependence for Au+Au / Cu+Cu. (N part scaling of R AA ) - Cronin effect in peripheral
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0 R AA, Central Events,Different √s WA98, EPJ C 23, 225 (2002) [ new reference compiled by D.d'Enterria nucl-ex/0403055] PHENIX, PRL 88 022301 (2002) No Suppression at 17 GeV (Au+Au) and 22 GeV (Cu+Cu)at medium p T Need more study for 17~62.4~ GeV data π 0 Au+Au π 0 Cu+Cu
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R AA Error notations: - Error bars: statistical error for HI spectra - Boxes: 1) sys. error for p+p reference. 2) sys. error for HI spectra. - Lines: N coll error (1 .) Moderate suppression for Au+Au 62.4 GeV, larger than one for Cu+Cu 62/22 GeV (p T > 2.0 GeV/c). π ± is similar to π 0
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Au+Au 200 GeV - Spectra for heavier particles has a convex shape due to radial flow. - Using Blast-wave fitting, try to estimate p/ ratio as a function of p T. (hydro p)/(hydro ) (hydro p)/(real ) NOTE: No weak decay feed-down correction applied. CentralPeripheral p T が2 GeV/c 以上の領域は、 hydrodynamics だけでは、 proton enhancement を説明できない。 →recombination や fragmentation の寄与 - Radial flow (ex. blast-wave fit) -
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Quark Recombination model (+Fragmentation) Example: –Fragmentation: D q→h (z) produces a 6 GeV/c from a 10 GeV/c quark –Recombination: produces a 6 GeV/c from two 3 GeV/c quarks produces a 6 GeV/c proton from three 2 GeV/c quarks Fries, et al, nucl-th/0301087 Greco, Ko, Levai, nucl-th/0301093 Mid pT 領域では、衝突で生成された quark が coalesce してハドロンを生 成しているモデル fragmentation recombination p/ Phenix preliminary
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summary Proton enhancement is observed in Au+Au/Cu+Cu collisions at 200/62 GeV. p/ ratios: 1.Only antiprotons in Cu+Cu 22.5 GeV system is different from others: No centrality dependence in p/ ratio at the intermediate pT. Central 0-10% p/ ratio agrees with the value in p+p collisions 2.Indicating a transition from soft to hard production at intermediate pT. 3.Npart scaling (dET/dy scaling) over different collision systems. 4.Recombination + radial flow would explain the p T, N part dependencies. Data indicates that an onset of baryon anomaly at RHIC is in between 22 GeV and 62 GeV.
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Spectra @High pT
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Introduction Cronin effect in nuclear. (Initial) Gluon interaction in hot dense matter. (final) The suppression at high pT is due to the final state interaction. Dependence on the System size ? Dependence on the particles species ? *PRL 91 072303 (2003) *No suppression in d+Au collision while Au+Au has factor 3 suppression at high pT. *Direct photon is not suppressed. PR L 94(2005)232301 Comparison between Au+Au and d+Au collision with high energy.
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Many measurements are done for high pT.
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Back up ~検出器・解析手法~
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PID charged p T spectra analysis in PHENIX Detectors: Drift Chamber, PC1, BBC and TOF for PID charged analysis. Centrality: Subdivided minimum bias triggered events, based on BBC charge (62 GeV), or the number of PC1 hit (22 GeV). Corrections: Geometrical acceptance, in flight decay. NOTE: No weak decay feed- down correction applied for all plots in this presentation. Charged particle identification by TOF Charge x Momentum (GeV/c) 1/ Cu+Cu @ 22.5 GeV
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PHENIX detector Aerogel Cherenkov (PID) EM Calorimeter (PID) TOF (PID) Drift Chamber (momentum meas.) Tracking detectors (PC1,PC2,PC3) - Central Arm Detectors (magnetic spectrometer) - Event Characterization detectors - PID (particle identification) is a powerful tool to study hadron production. p (p) ID up to 7 GeV/c - p (p) ID up to 4 GeV/c - Time of Flight (TOF) Veto for proton ID π+π+ K+K+ p Aerogel Cherenkov (ACC)
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Back Up ~ 説明 ~
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R AA Normalization / inel p+p nucleon-nucleon cross section 1. Compare Au+Au to nucleon-nucleon cross sections 2. Compare Au+Au central/peripheral Nuclear Modification Factor: If no “effects”: R AA < 1 in regime of soft physics R AA = 1 at high-p T where hard scattering dominates Suppression: R AA < 1 at high-p T AA
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What is the definition of baryon anomaly at RHIC? p T region of interest is the intermediate p T (2.0 - 5.0 GeV/c). p/ (p/ ) ratios are much larger than the fragmentation expectations (p+p). –Strong centrality dependence in heavy ion data. Different nuclear modification factor (R CP or R AA ) between pions and (anti)protons. –Pions: suppression. –(anti)protons: no suppression.
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probe rest frame r/ gg g Color Glass Condensate Gluon fusion reduces number of scattering centers in initial state. Theoretically attractive; limits DGLAP evolution/restores unitarity
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Back up ~結果~
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p T spectra in p+p 62.4 GeV Data from Run-6 (2006) at RHIC. Provides an important baseline for p T spectra in Au+Au and Cu+Cu at s NN = 62.4 GeV. Presented the invariant yields here. Working on the determination of inelastic cross section and trigger bias in PHENIX experiment for the absolute normalization in p T spectra. * No weak decay feed-down correction applied.
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p T spectra (Cu+Cu √s NN = 200 GeV) NOTE: No weak decay feed-down correction applied. Phenix preliminary - p T reach extended for (anti-)protons with fine centrality bins. <= (1) Aerogel Cherenkov, (2) Enough statistics in Au+Au/Cu+Cu (Anti-) protons ACC
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p T spectra (p+p √s = 200 GeV) - High statistics 200 GeV p+p data. More than10 times statistics used compared to previous Run3 p+p analysis. - The p+p data provides baseline spectra to heavy ion data, and it is important to quantify in-medium nuclear effects in heavy ion collisions at RHIC. NOTE: No weak decay feed-down correction applied. Phenix preliminary TOF
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Medium II: Thermalization Hadron yields and spectra are consistent with thermal emission from a strongly expanding source. The observed strangeness production is consistent with complete chemical equilibrium /K/p measurement in a Broad pt range Stat. model fit:T ch ~ 160MeV, s ~1.0 Strangeness saturation at RHIC? stronger radial flow at RHIC? Expansion velocity T kin ~ 100 MeV ~ 0.5 Chemical freezeout Thermal freezeout RHIC
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p/ ratios in p+p 62.4 GeV
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R AA for charged pions (by ISR fit) Error notations: - Error bars: statistical error for HI spectra - Boxes: 1) sys. error for p+p reference. 2) sys. error for HI spectra. - Lines: N coll error (1 .) Used ISR fit (nucl- ex/0411049, D. d’Enteria) for p+p parameterization. Using ISR fit: Moderate suppression for Au+Au 62.4 GeV, larger than one for Cu+Cu 62/22 GeV (p T > 2.0 GeV/c). * No weak decay feed-down correction applied.
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R AA for antiprotons (by ISR fit) Used ISR data at 63 GeV (Alper. NPB 100, 237) for p+p reference. Similar R AA for all three systems. * No weak decay feed-down correction applied.
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R AA for protons (by ISR fit) Used ISR data at 63 GeV (Alper. NPB 100, 237) for p+p reference. Largest R AA for Cu+Cu 22.5 GeV. R AA for Au+Au 62.4 GeV is smaller than that in Cu+Cu 62.4 GeV. * No weak decay feed-down correction applied.
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p/ vs. p T (Low p T ) At low p T, p/ shows weak and decreasing N part dependence because inverse slope (from m T exponential fitting) also shows it. NOTE: No weak decay feed-down correction applied. - Radial flow - (Anti-)protons TOF Phenix preliminary
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Recombination model と結果の比較 Fries, R et al PRC 68 (2003) 044902 Greco, V et al PRL 90 (2003) 202302 Hwa, R et al PRC 70(2004) 024905 etc. Hydro + Recombination + Fragmentation で、説明できるか?? Au+Au 200GeV STAR preliminary
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