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Strange Particle Ratios on the Near- & Away-Sides of

Jets at RHIC

Jiaxu Zuo Shanghai Institute of Applied Physics & BNL

(For STAR Collaboration)

SQM 2007, Levoča, SlovakiaSQM 2007, Levoča, Slovakia

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Outline

• Motivation

• Analysis Method

• Results & Discussions

• Summary

• STAR Au+Au 200GeV Year 2004 Running Data

• ~13M Events

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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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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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Analysis method

Step 1: 3-D histogram with , , and minv (Trigger-V0 pair)

Step 2: Project over a given rangein this talk I show results for -1<<1: (combine jets & some ridge)

Step 3: Plot minv vs. Fit the minv distribution yield dN/d ( KS

0, , or )

minv

minvStep 4: Repeat 1 to 3 with mixed eventsStep 5: Scale the mixed event background with measured v2

Subtract off the background • ZYAM (zero-yield at the minimum) • ZYA1 (zero-yield at one )

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Hadron_Ks & + Correlation

• Centrality Dependence– Double bump -> Broadened -> Singly-peaked– The shape consistent with di-hadron correlation

peripheral

3<pT,trig<6 GeV/c; 1<pT,ass<4 GeV/c

central

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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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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)

Both STAR and PHENIX results consistent with larger B/M ratio on the Away-Side than Near-Side.

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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?• Sound wave excitation particles maybe slower than the speed of sound (vs=c/3)

• 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

M. Horner, QM06

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B/M Ratio in Distribution

???

away

nearM

edium

mach cone

Δ= Trigger

Δ = /2

Medium

Ass

ocia

te

• A slope at Away-Side? A slope at Away-Side? Slow particle Double bump Slow particle Double bump KKSS

00 Fast particle Double bump ?? Fast particle Double bump ??• 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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• (B/M)A to (B/M)N double ratio from central to peripheral– 00-10% &10-40%

• Maybe a slope here

– 40-80% • Difficult to describe

• In the correlation function,– 00-10% &10-40%

• There is a double bump and broadened away-side.

– 40-80% • There seems to be a single peak.

(B/M)A to (B/M)N double ratio

pe

riph

era

lc

entra

l

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• Centrality Dependence– Double bump, Broadened & Singly-peaked– The shape consistent with di-hadron correlation

Hadron_ & Correlation

peripheral

3<pT,trig<6 GeV/c; 1<pT,ass<4 GeV/c

central

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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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• (B/B)A to (B/B)N ratio from central to peripheral

• The ratio is around one• Maybe a slope at here,

but error bars are still too large to conclude.

Why is it a slope?? • Independent of v2 and

background subtraction method

(B/B)A to (B/B)N ratio

pe

riph

era

lc

entra

l

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Summary• Measured the Conditional Yields of identified associate particles on the

near- and away-side of jets• From central to peripheral : Double bump -> Broadened -> Singly-peaked• Extracted particle ratios on the near and away-side• Systematic errors from v2 and background normalization are large

– errors can be reduced with more data (to reduce error on the level of the background)

– and better understanding of v2 (to reduce uncertainty on the shape of the background)

• Both STAR and PHENIX results consistent with larger B/M ratio on the away-side than near-side

• Shape of away-side has been studied– some indication of a slope for B/M and / on the away-side (mach-cone?

gluon vs. quark? Or others?)– slope of B/M and / on the away-side seems to be independent of v2 and

background subtraction method

Thanks!!Thanks!!Acknowledgments: STAR Collaboration Acknowledgments: STAR Collaboration Dr. Paul Sorensen Dr. Paul Sorensen

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The Collaboration

Shanghai Institue of Applied Physics - Argonne National Laboratory Institute of High Energy Physics - University of Birmingham - Brookhaven National Laboratory - California Institute of Technology - University of California, Berkeley - University of California, Davis - University of

California, Los Angeles - University of Illinois at Chicago - Carnegie Mellon University - Creighton University – Nuclear Physics Inst., Academy of Sciences - Laboratory of High Energy

Physics - Particle Physics Laboratory - University of Frankfurt - Institute of Physics, Bhubaneswar - Indian Institute of Technology, Mumbai - Indiana University Cyclotron Facility -

Institut de Recherches Subatomiques de Strasbourg - University of Jammu - Kent State University - Institute of Modern Physics - Lawrence Berkeley National Laboratory -

Massachusetts Institute of Technology - Max-Planck-Institut fuer Physics - Michigan State University - Moscow Engineering Physics Institute - City College of New York - NIKHEF and

Utrecht University - Ohio State University - Panjab University - Pennsylvania State University - Institute of High Energy Physics - Purdue University – Pusan National University - University of Rajasthan - Rice University - Instituto de Fisica da Universidade de Sao Paulo - University of

Science and Technology of China - SUBATECH - Texas A&M University - University of Texas, Austin - Tsinghua University - Valparaiso University – Variable Energy Cyclotron Centre,

Kolkata - Warsaw University of Technology - University of Washington - Wayne State University - Institute of Particle Physics - Yale University - University of Zagreb -UNICAMP

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Backup

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V0 reconstructionV0s from UCLA/LBL picoDsts

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a.u.

pTtrig=3-6 GeV/c,

1.5 GeV/c <pTassoc< pT

trig

Au+Au central @ 200 GeV

ridge

ridge

jet

jet+ridge after v2 subtraction

jetridge

v2 + away-side peak

h-h

Au+Au: long-range correlations at near side (“the ridge”)

Lesson: The near-side jet does interact with the medium

Fragmentation and energy loss - near-side

Di-hadron correlations

trigger

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Ks, & Hadron v2 • Background: V0 & Hadron v2

• Background function: B()=b0(1+2<v2

A*v2B>cos(2))

• Final results background: Average v2 – Ks and v2{EP} & v2{LYZ}– Charged Hadron: v2{EP} & v2{4}

• A part of systematic errors will be calculated by the v2{EP} & v2{LYZ}, v2{4}

Weight average flow:

v2 Hadron Ks Lambda

00-100.0811912+-0.00736462

0.04393416+-0.000463404

0.0459624+-0.000490826

10-400.151251+-0.00175313

0.104353+-0.000916851

0.105984+-0.00108642

40-800.235884+-

0.0013962480.1222672+-0.000545339

0.144212+-0.000647908

• V0 LYZ v2: pt [1,4]• Hadron v2{4}: pt [3.2,6.5]

v2{4} & v2{EP} Phys. Rev. C 72 (2005) 014904 v2{LYZ} paper in preparation

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• Lee-Yang Zeroes method is less biased by non-flow correlation.

Nucl. Phy. A 727 (2003) 373-426

• Sum generating function:– Flow vector projection into arbitrary angel .

– Generating function for a given .

• Integrated flow: – From the first minimum r0

• Differential flow

Lee-Yang Zeroes method

First minimum of |G|2 determines r0

all events

average over

all particles in all events

average over removes acceptance effects

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Same Event & v2 BackgroundS

TA

R p

relim

inar

y

for these plots, efficiency correction not applied

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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