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CCAST Beijing,. Identified Di-hadron Correlation in Au+Au & PYTHIA Simulation. Jiaxu Zuo Shanghai Institute of Applied Physics & BNL. Outline. Motivation Results & Discussions Correlation in PYTHIA Summary. leading particle. hadrons. q. q. hadrons. leading particle. - PowerPoint PPT Presentation
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Identified Di-hadron Correlation in Au+Au &
PYTHIA Simulation
Jiaxu Zuo Shanghai Institute of Applied Physics & BNL
CCAST Beijing, CCAST Beijing,
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hadrons
q
q
hadrons
leadingparticle
leading particle
p+p collision
hadrons
q
q
hadrons
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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Di-hadron correlations
For high pT: away-side correlation is gone!back-to-back jets are quenched
At lower pT: away-side correlations returnbut they are highly modified with a double
bump!?We will try to understand what causes this behavior
pT,trig>4 GeV/c pT,ass>2 GeV/c
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pT,trig>2.5 GeV/c pT,ass>1.0 GeV/c
STAR preliminary
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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.
pT,trig>2.5 GeV/c pT,ass>1.0 GeV/cM. Horner, QM06
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STAR preliminary
B/M Ratio Intermediate pT
large enhancement of baryon/meson ratio in central Au+Au relative to p+preaches maximum at pT~3 GeV/c
Perhaps related to faster increase with centrality of baryon production from recombination
Intermediate pT, Baryon & Meson:Grouping of RCP and v2
----recombination pictures
Can recombination explain particle ratios in the jet cones?
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Anti-B/B Ratio Intermediate pT
We can also learn about gluons vs quarks from B/B ratios with the jet correlation.
For example: anti-baryons dominated by gluon jetsbaryons mixture of quark and gluon
STAR preliminary
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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 preliminaryH.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
ppTmpd B //exp/
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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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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, pT>3.0 GeV/c
•Associate: KS0, , or (i.e. V0 decay), pT>1.0 GeV/c
parton
trigger hadron
Λ, Λ, K0S
Λ, Λ, K0S
parton
near-side associated
away-side associated
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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-Side Away-Side
(+)/Ks0.77 0.12 (stat) 0.18
(sys)1.7 0.3 (stat) 0.6
(sys)
Near-Side Away-Side
3<pT,trig<6 GeV/c 1<pT,ass<4 GeV/c
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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-Side Away-Side pT=1.5GeV/c
/ 0.92 0.20 (stat) 0.20 (sys)
0.89 0.17 (stat) 0.37 (sys)
0.76 0.013
Near-Side Away-Side
3<pT,trig<6 GeV/c 1<pT,ass<4 GeV/c
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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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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<pT,trig<6 GeV/c 1<pT,ass<4 GeV/c
3<pT,trig<6 GeV/c 1<pT,ass<4 GeV/c
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The shape of the ratio
away
near
Medium
mach cone
Mediumaway
near
deflected jets
Can we learn something about the shape on the away-side?• For our pT range slower particles would have to be heavy
For production from sound wave excitation the bumps should have mostly heavy particles (+)/KS
0 would get large in the bump region
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pT,trig>2.5 GeV/c pT,ass>1.0 GeV/c
STAR preliminary
• Mach Cone Concept/Calculations
Stoecker, Casalderry-Solana et al; Muller et al.; Ruppert et al., …
• Cherenkov RadiationMajumder, Koch, & Wang; Vitev
• Jet Deflection (Flow) Fries; Armesto et al.; Hwa
• Strong Parton Interaction
G.L. Ma, S. ZhangM. Horner, QM06
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B/M Ratio in Distribution
away
nearM
edium
mach cone
Δ= Trigger
Δ = /2
Medium
Ass
ocia
te
• B/M ratio: Away-Side seems to increase in the "cone" region - as it maybe for B/M ratio: Away-Side seems to increase in the "cone" region - as it maybe for sound wave excitation. sound wave excitation.
• Increased B/M ratio may also be consistent with recombination in high density Increased B/M ratio may also be consistent with recombination in high density region of the shock-waveregion 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 v2 background from three different methods
• The shape of Baryon to Meson ratio on the away-side seems to be independent of v2 background and background subtraction method.
• Perhaps a slope , but error bars are still too large to draw conclusions.
+KS0
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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
Preliminary Results
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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
Preliminary Results
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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 v2 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!!Thanks!!
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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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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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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:– RatioLbar/L > Ratiopbar/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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