Hadron production by quark combination in Pb+Pb collisions at

SPS

十三届中高能核物理会议 安徽合肥 ， 11.5-11.7 ， 2009

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邵凤兰 曲阜师范大学

C.E.Shao, J.Song, F.L.shao, Q.B.Xie, Phys. Rev. C 80, 014909 (2009)

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Outline• Introduction

• Quark combination rule and symmetry

• Results and discussions

• Summary

(3)fSU

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initial state

pre-equilibrium

QGP andhydrodynamic expansion

hadronization

hadronic phaseand freeze-out

Exploring QGP Matter at RHIC

Introduction

Studying hadronization mechanism

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(3) Thermal hadrons

(2) thermal photons

approaches

(1) high jetsTp

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PRL97,152301(2006), STAR

some experimental phenomena at RHIC:

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PRL98,162301(2007), STAR

KET =mT -m

Difference in baryon and meson v2.

Perfect scaling for all measured hadrons

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1 2 3 Bp p p p

1 2 Mp p p

• R. Hwa, C. B. Yang (recombination)• R. J. Fries, et al., (recombination)• C. Ko, L. W. Chen, et al. (Coalescence)• Q. B. Xie, F. L. Shao (SDQCM)

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Some experimental evidences at SPS

2. quark number scaling of V2

17.3 GeV

1. Energy density （ top SPS---158AGeV）

≈3

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3. Onset of deconfinement at lower SPS （ 30 AGeV）

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Quark combination rule and symmetry

(3)fSU

near correlation in phase space

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W.Han, S.Y.Li, Y.H.Shang, F.L.Shao, T.Yao, Phys. Rev. C 80, 035202 (2009)F.L.Shao, Q.B.Xie, Q.Wang, Phys. Rev. C 71, 044903 (2005)T.Yao,W.Zhou, Q.B.Xie, Phys. Rev. C 78, 064911 (2008)

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Results and discussions

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yields

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Rapidity distribution

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pT spectra

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B/M ratio

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Central Au+Au collisions at 200 GeV

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Exploring QGP matter properties

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Collective flow

u,d s

The collective flow of strange quarks is stronger than that of light quarks; this result is similar to that obtained at RHIC.

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strangeness

The strangeness is almost the same.

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Summary

● The combination mechanism can describe the hadron

production at RHIC and SPS energies.

● The collective flow of strange quark is stronger than that for light quarks; The strangeness is almost the same from SPS to RHIC energies.

Thank you !

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Issues faced by the combination mechanism ：

Entropy and energy conservation

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If they are close to each other in phase space, they can interact with sufficient time to be in the color singlet and form a meson.

baryon. If the neighbor is a q, because the attraction strength of the singlet is two times that of the antitriplet, then qq will win the competition to form a meson and leave a q alone to combine with other quarks or antiquarks.

Quark combination rule and SU_f(3 ) symmetry

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• V. V. Anisovich, et al.,(1973)• J. D. Bjorken, et al., (1974)• K. P. Das & R.C. Hwa (1977)• Q. B. Xie, et al. (1980’s)

in RHIC, for “QGP” hadronization

• R. Hwa, C. B. Yang, et al., (recombination)

• R. J. Fries et al., (recombination)

• C. Ko, L. W. Chen, et al. (Coalescence)• Q. B. Xie, F. L. Shao (SDQCM)

quark combination mechanism

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Quark combination model

Momentum distributions of quarks

Combination rule：Near correlation in rapidity

( ) (2 1) iri i sC M J

( ) iri i sC B

( )M qq

decay finalhadron

( )B qqq

(3)fSU

qqN

: : 1:1:u d s sN N N

The smaller the difference in rapidity for two(three) quarks, the longer is the interaction time. So there is enough time for a to be in a color singlet and form a meson(baryon).

)(qqqqq

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4 ） QCM 面临的普适性挑战

• 扩展到不同能量 ( LHC ) ，不同中心度

• RHIC 能量不同快度、不同 pT, 尤其是大、小 pT 下的强子谱

• 回过头来到 ( RHIC,Tevtron,LHC ), e+- e-,p p pp

• 最重要的一个挑战是用到宇宙学。 RHIC 和 LHC 研究 QGP 本来就是为了了解宇宙初期的物质状态 ，它的 强子化应该体现为宇宙演化的结果。

强子化机制的普适性是粒子物理、核物理、宇宙学的连接点和切入点。

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The average constituent quark number :

where

backup slides ---1

λs is the strangeness suppression factor

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Stationary thermal source

Integrating over rapidity

backup slides ---2

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backup slides ---3Integrating over the transverse components

nonuniform longitudinal flow

where w(y) is phenomenological expansion function

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backup slides ---6

perturbative QCD calculation :

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PHENIX Data-SetsPHENIX Data-Sets

Collided 4 different species in 8 years: AuAu, dAu, pp, CuCu6 energies run: 9.2 GeV, 19 GeV, 22.5 GeV, 62.4 GeV, 130 GeV, 200 GeV

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times

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times

Year Species Ćs [GeV ] ŗLdtNtot (sampled)Data SizeRun1 2000 Au - Au 130 1 µb-1 10 M 3 TB

Au - Au 200 24 µb-1 170 M 10 TBAu - Au 19 < 1 M

p - p 200 0.15 pb-1 3.7 B 20 TBd - Au 200 2.74 nb-1 5.5 B 46 TBp - p 200 0.35 pb-1 6.6 B 35 TB

Au - Au 200 241 µb-1 1.5 B 270 TBAu - Au 62.4 9 µb-1 58 M 10 TBCu - Cu 200 3 nb-1 8.6 B 173 TBCu - Cu 62.4 0.19 nb-1 0.4 B 48 TBCu - Cu 22.4 2.7 µb-1 9 M 1 TB

p - p 200 3.8 pb-1 85 B 262 TBp - p 200 10.7 pb-1 233 B 310 TBp - p 62.4 0.1 pb-1 10 B 25 TB

Run-7 2007 Au - Au 200 725 µb-1 4.6 B 570 TBd - Au 200 81 nb-1 160 B 437 TBp - p 200/500

Au - Au low energy

Run5

Run-6

Run-8

2002/03

2006

2007/08

2005

2001/02Run2

Run3

Run4 2003/04