identified di-hadron correlation in au+au & pythia simulation

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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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Outline

• Motivation

• Results & Discussions

• Correlation in PYTHIA

• Summary

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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

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.0.2

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are needed to see this picture.

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


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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.



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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


are needed to see this picture.0.2

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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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Backup

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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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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

identified di-hadron correlation in au+au & pythia simulation

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