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1 Identified Di-hadron Correlation in Au+Au & PYTHIA Simulation Jiaxu Zuo Shanghai Institute of Applied Physics & BNL CCAST Beijing,
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2 Outline Motivation Results & Discussions Correlation in PYTHIA Summary
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3 hadrons q q leading particle leading particle p+p collision hadrons q q Leading particle suppressed leading particle suppressed Au+Au collision Jet in p+p & Au+Au Jet –p+p collisions, the hard scattering of quarks and gluons Jet quenching: –The hard jet loses a significant amount of its energy via radiating gluon induced by multiple scattering.
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4 Di-hadron correlations For high p T :away-side correlation is gone! back-to-back jets are quenched At lower p T :away-side correlations return but they are highly modified with a double bump!? We will try to understand what causes this behavior p T,trig >4 GeV/c p T,ass >2 GeV/c 0.2 0.6 0.4 0.0 p T,trig >2.5 GeV/c p T,ass >1.0 GeV/c STAR preliminary
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5 Centrality dependence Singly-peaked -> broadened -> becomes doubly bump What’s the baryon/meson ratio in the near- and away-side peak? What are the anti-baryon-to-baryon ratios? We will measure the ratios to try to understand the source of the correlations in different centralities. p T,trig >2.5 GeV/c p T,ass >1.0 GeV/c M. Horner, QM06
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6 STAR preliminary B/M Ratio Intermediate p T large enhancement of baryon/meson ratio in central Au+Au relative to p+p reaches maximum at p T ~3 GeV/c Perhaps related to faster increase with centrality of baryon production from recombination Intermediate p T, Baryon & Meson: Grouping of R CP and v 2 ----recombination pictures Can recombination explain particle ratios in the jet cones?
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7 Anti-B/B Ratio Intermediate p T We can also learn about gluons vs quarks from B/B ratios with the jet correlation. For example:anti-baryons dominated by gluon jets baryons mixture of quark and gluon STAR preliminary
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8 Anti-Baryon Density Collisions which contain ggg, qbar+g or qqbar+g processes have higher anti-baryon phase space density Anti-baryon phase space density from collisions involving a gluon is much higher than those without a gluon STAR preliminary H.D.Liu QM06 From B/B ratios in the correlation Baryon & Anti-baryon production with Jets Gluon vs. Quarks with Jets H. Liu, Z. Xu nucl-ex/0610035
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9 Gluon Jets Vs. Quark Jets PYTHIA: gluon jets: baryon-meson splitting quark jets: mass splitting. STAR data: baryon-meson splitting Gluon jet Quark jet predicts a slight dependence for / dominated by the gluon jet events. PYTHIA in the correlation Quark jets & Gluon jets in the correlation Correlation particle ratio in the PYTHIA with different jets Baryon & Meson in the correlation STAR, Phys Lett B, 637 (2006) 161
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10 Trigger-associate correlations Identified particles correlations & B/M, B/B ratio can provide additional information on: jet quenching baryon/meson enhancement at STAR particle production mechanisms Di-hadron correlation Away-side shape We’ll study identified associate particles using Trigger: Charged hadron, p T >3.0 GeV/c Associate: K S 0, , or (i.e. V 0 decay), p T >1.0 GeV/c parton trigger hadron Λ, Λ, K 0 S parton near-side associated away-side associated
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11 Hadron_Ks & + Correlation Centrality bin: 10-40% The yellow band : systematic error From the line: Left part: near-side Right part: away-side Particle Ratios Near-SideAway-Side ( + )/Ks0.77 0.12 (stat) 0.18 (sys)1.7 0.3 (stat) 0.6 (sys) Near-SideAway-Side 3<p T,trig <6 GeV/c 1<p T,ass <4 GeV/c
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12 Hadron_ & Correlation Centrality bin: 10-40% The yellow band: Systematic error. From the line: Left part: near-side Right part: away-side Particle Ratios Near-SideAway-Sidep T =1.5GeV/c // 0.92 0.20 (stat) 0.20 (sys)0.89 0.17 (stat) 0.37 (sys)0.76 0.013 Near-SideAway-Side 3<p T,trig <6 GeV/c 1<p T,ass <4 GeV/c
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13 STAR Preliminary Baryon to Meson Ratio with Jets Lambda to Ks Ratio : Away-Side > Near-Side Anti-Proton to Ratio : Away-Side > Near-Side (PHENIX) Away-Side ~ Au+Au Near-Side ~ p+p B/M ratio in Near-Side & Away-Side: | |<1.0 –Away-Side > Near-Side –Near-Side: Au+Au ~ p+p –Away-Side ~ inclusive B/M ratio in Jet and Ridge: –Jet ~ p+p –Ridge ~ inclusive in Au+Au C. Nattrass QM2008
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14 B/M & Bbar/B Ratio with Jets B/M ratio: Near-side : independent with the Npart Away-side: increase with the Npart parton density increase Bbar/B ratio: Near-side and Away-side seems consistent. Also seems independent with the Npart with in the errors. 3<p T,trig <6 GeV/c 1<p T,ass <4 GeV/c
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15 The shape of the ratio away near Medium mach cone Medium away near deflected jets Can we learn something about the shape on the away-side? For our p T range slower particles would have to be heavy For production from sound wave excitation the bumps should have mostly heavy particles ( + )/K S 0 would get large in the bump region 0.2 0.6 0.4 0.0 p T,trig >2.5 GeV/c p T,ass >1.0 GeV/c STAR preliminary Mach Cone Concept/Calculations Stoecker, Casalderry-Solana et al; Muller et al.; Ruppert et al., … Cherenkov Radiation Majumder, Koch, & Wang; Vitev Jet Deflection (Flow) Fries; Armesto et al.; Hwa Strong Parton Interaction G.L. Ma, S. Zhang M. Horner, QM06
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16 B/M Ratio in Distribution away near Medium mach cone Δ=Δ= Trigger Δ = /2 Medium Associate B/M ratio: Away-Side seems to increase in the "cone" region - as it maybe for sound wave excitation.B/M ratio: Away-Side seems to increase in the "cone" region - as it maybe for sound wave excitation. Increased B/M ratio may also be consistent with recombination in high density region of the shock-waveIncreased B/M ratio may also be consistent with recombination in high density region of the shock-wave Error bars too large to get strong conclusionsError bars too large to get strong conclusions The same shape in the away-side using v 2 background from three different methods The shape of Baryon to Meson ratio on the away-side seems to be independent of v 2 background and background subtraction method. Perhaps a slope, but error bars are still too large to draw conclusions. + K S 0
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17 Identified Correlation in PYTHIA Correlation function: –particle dependence –Clearly away-side peak ~ p+p data in STAR Quark & Gluon Jet: –gluon jet > quark jet Quark jet: pp->qq Gluon jet: pp->gg Preliminary Results
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18 Identified Correlation in PYTHIA Pbar/pion Ratio –Near-Side > Away-Side –Gluon jet ~ ee->ggg –Quark jet ~ ee->qqbar –Gluon jet > Quark jet Anti-Lambda/Lambda Ratio –Almost consistent with STAR data –Gluon jet: Near < Away –Quark jet: Away > Near –Quark jet > Gluon jet Preliminary Results
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19 Summary Measured the Conditional Yields of identified associate particles on the near- and away-side of jets Extracted particle ratios on the near and away-side –Away-Side ~ Au+Au –Near-Side ~ p+p B/M ratio: –Near-side : independent with the Npart –Away-side: increase with the Npart => parton density increase Shape of away-side has been studied –some indication of a slope for B/M on the away-side (mach-cone? gluon vs. quark? Or others?) –slope of B/M on the away-side seems to be independent of v 2 and background subtraction method Di-Hadron in PYTHIA –Correlation Conditional yields: gluon jet > quark jet –Particle ratios with jet => energy loss in the gluon & quark anti-baryon production with jet strangeness production with jet Thanks!!
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20 Backup
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21 Correlation Physics Hard scatterings in p+p collisions produce back-to- back "jets" of particles In nuclear collisions, jets instead serve as a penetrating probe of the extremely dense nuclear matter Comparing characteristics of jets in nuclear collisions to jets in p+p collisions has uncovered special properties of dense nuclear matter. Azimuthal correlations
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22 Ratio vs. B/M Ratio at Near-Side B/M Ratio vs. at Away-Side B/B Ratio at Near-Side B/B Ratio vs. at Away-Side
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23 Strange particle ratio with Jet Anti-B/B Ratio Pbar/p: –Near > Away –Near: gluon jet ~ quark jet ~ 1.0 –Away: gluon jet > quark jet –Gluon jet: Near ~ Away Lbar/L: –Ratio Lbar/L > Ratio pbar/p –Near > Away –Quark jet > Gluon jet –Gluon jet: Near < Away Preliminary Results STAR Data Energy loss: gluon & quark Strangeness production: gluon & quark
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24 Particle Ratio with Correlation B/M ratio in Near-Side & Away-Side: | |<1.0 –Away-Side > Near-Side –Near-Side: Au+Au ~ p+p –Away-Side ~ inclusive B/M ratio in Jet and Ridge: –Jet ~ p+p –Ridge ~ inclusive in Au+Au Jet like p+p Ridge like bulk Away-Side ~ Ridge
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