Strange quark dynamics on hot dense matter under the extreme condition

Yu-Gang Ma (马余刚 )

The 5-th International Conference on Quarks and Nuclear Physics – QNP09,IHEP@Beijing, September 21– 26, 2009

(SINAP)Main collaborators: Jin-Hui Chen, Guo-Liang Ma

Outline

Hot dense matter under the extreme condition

Strange -quark dynamics from -meson and baryon

— s-quark thermalization: production and (PT)

— s-quark collectivity: grouping behavior of elliptic flow —s-quark enhancement: -meson enhancement— s-quark un-polarization: -meson spin un-alignment— s-quark transverse momentum distribution:(PT/n)— Constraints on the system evolution dynamics

Summary/outlook

3

Energy loss leads to re-Energy loss leads to re-distribution of Soft associated distribution of Soft associated particlesparticles

→→ enhancement enhancement

((strong jet-medium interaction)

Hard associated particles Hard associated particles →→ suppression suppression

(partonic energy loss)

Associated particleson away side:

Trigger particleHot Dense Matter under the extreme condition @RHIC: (1) Away-side peak vanishes in Au-Au central collision

4 >pT(assoc) > 2 GeV/c

4 <

p T(t

rig)

< 6

GeV

/c

4 >pT(assoc) > 0.15 GeV/c

STAR coll, PRL 95 (2005)152301

4

<Nbinary>/inelp+p

nucleon-nucleon cross section

Nuclear Modification Factor:

AA

hadronsleadingparticle

q

q

?

If R = 1 here, nothing new going on

Hot Dense Matter under the extreme condition: (2) Strong suppression of the High pT particles

Why -meson ?

[1] A. Shor, Phys. Rev. Lett. 54 (1985) 1122[2] J. Adams et al., Phys. Lett. B 612 (2005) 181

K+

K-

K-

K+

φ

φφ

K+K-

QGP

The -meson is a clean probe from early time:● Small for interactions with non-strange

particles[1]

● Relatively long-lived (41 fm/c) →decays outside the fireball

● Previous RHIC measurements have ruled out K+K- coalescence as production mechanism[2]

The can provide info on particle production mechanisms/medium constituents:● Theis a meson but as heavy as , p

baryons (mass vs. particle type?)

Hot Dense Matter

The STAR experiment

Event-mixing method used to estimate combinatorial background from uncorrelated K+K- pairs;

Final subtracted minv

distribution fitted with Breit-Wigner + straight line.

We used the high-statistics 200 GeV and 62.4 GeV Au+Au and Cu+Cu data to measure the -meson production at STAR

STAR TPC used to identify Kaon via dE/dx in TPC gas

STAR Detector

7

-meson production at RHIC

<pT>

/K-

N()/N(K-), ruled out the K+K-coalescence(red dashed line: UrQMD assumes K+K- coalescence mechanism for phi

.

UrQMD

Evolution in the centrality dependence:Clear change in spectral shape-- Exponential (~thermal) for central collisions-- Power law type (~ hard process) at high pT inperipheral collisions STAR Col. Phys. Lett. B 612, (2005) 181,

Phys. Rev. Lett. 99, (2007) 112301

<pT>: -meson decoupled early

-meson RCP

RCPmid-central collisions:

RCP of meson is more consistent with that of K0 rather than supporting the baryon/meson grouping behavior.

The observable favors the prediction based on quark Coal/Recom model (s-sbarphi).

peripheral collisions:

The binary scaled production is very similar to that in p+p and d+Au collisions where strangeness production may be canonically suppressed.

Therefore a baryon-meson scaling behavior of RCP is not expected.

SINAP & LBL et al. (for STAR), PRL 99 (2007)112301

Thermalization: ’sare mostly from bulk thermal s quarks

At intermediate pT, (sss) and (ss) should be dominated by bulk thermal quark coalescence – no jet contribution

(Hwa and Yang PRC 75, 054904 (2007))

It appears that thermal quark coalescences dominate the particle production below

pT~4 GeV/c in central Au+Au collisions

SINAP & LBL et al. (for STAR), PRL 99 (2007)112301

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Collectivity of quarks: Partonic Collectivity of multi-strange particles

STAR data (S. Shi et al)PHENIX π and p: nucl-ex/0604011v1NCQ inspired fit: X. Dong et al. Phy. Let. B 597 (2004) 328

J. H. Chen, YGM et al., PRC74, 064902(2006); J. X. Zuo, J.Y.Chen, X. Cai, YGM, F. Liu et al., EPJC 55,463(2008)

Partonic transport model (AMPT Model) calculations:1. NCQ scaling works well for phi/Omega: strange quark collectivity;2. Larger v2 reveals in comparison with AMPT default and RQMD case. Partonic interaction is essential to reproduce larger v2 as the data!

px

pyy

x

Strangeness enhancement

We do observe strangeness enhancement: yield relative to p+p

BUT -meson enhancement:

-- Enhancement between net Strangeness = 1 () and 2 () particles

-- 200 GeV data > 62.4 GeVThe above observations clearly suggest that, at these collision energies, the source of enhancement of strange hadrons is related to the formation of a dense partonic medium in highenergy nucleus–nucleus collisions and cannot be alone due to canonical suppression of their productionin smaller systems.

SINAP & LBL et al. (for STAR), PLB 673 (2009)183

12

Global orbital angular momentum

b/RA

-Ly i

n un

it of

105

x

zimpact parameter b

• gradient in pz-distribution along the x-direction• local orbital angular momentum of the created parton• quark polarized via spin-orbit?• final state hadron polarization?

– hyperon polarization – vector meson spin alignment

Huge orbital angular momentumof the collisions system may lead to global quark polarization of the system

Z.T. Liang (Shandong), X.N. Wang et al., PRL 94, 102301(2005); PLB 629, 20 (2005); arXiv0710.2943[nucl-th].

13

What happen in Experiment?

Lambda un-polarization

|PL|<0.02

Voloshin et al (STAR Col.) PRC 76, 024915 (2007)

Vector meson spin alignment：Deviation of ρ00 from 1/3 manifests the alignment of vector mesons;

No evidence is found for the transfer of the orbital angular momentum of the colliding system to the vector meson spins.

J.H. Chen (SINAP), Z. Tang (USTC), I. Selyuzhenkov (STAR), PRC77, 061902(R) (2008)

Un-polarization signal of s-quark might imply that the system created at RHIC is isotropic to the extent that, locally, there is no longer a preferred direction. It favors the QGP scenario.

Strange quark PT distributions at Hadronization

)2/(

)3/(

)2/(

)3/(

T

T

T

T

p

pd

p

ps

Can we extract the strange quark pT distribution from multi-strange hadron data? If baryons at pT are mostly formed from coalescence of partons at pT/3 and mesons at pT are mostly formed from coalescence of partons at pT/2, then we could extract quark PT information:

and particles have no decay feed-down contribution!These particles will freeze-out earlier from the system and have small hadronic rescattering cross sections.

SINAP, PRC 78 (2008)034907

15

The constitute quark pT distributions have been extracted from the multi-strange data;

The s-quark shows a flatter pT distribution than the d-quark.

Strange and light quark distribution

The s-quark and d-quark have a similar KET distribution: partons have undergone a partonic evolution possibly described by hydrodynamics.

16

s/d quark ratio from primordial hyperon

s/d ratio from hyperon 0(1530) feed-down[1]: 46%+-14% Consistent s/d ratio derived from primordial hyperon data

[2] B.I. Abelev et al., Phys. Rev. Lett. 97, 132301 (2006);

[3] S. Wheaton and J. Cleymans, J. Phys. G 31, S1069 (2005);

[4] M. Bleicher et al., J. Phys. G 25, 1859 (1999); H.J. Drescher et al., Phys. Rep. 350, 93 (2001).

– feed-down: –(1385)[2]: 26%+-5.9%;–0: no data available yet

–THERMUS[3]: 36%– String frag[4]: 25%

[1] R. Witt, J. Phys. G 34, S921 (2007);

17

s/d ratio compared with Reco. model calculation

Quark Reco. model predicted a consistent shape between s/d ratio and the hyperon ratio.

Good agreement with the data; Large exp. uncertainty;

18

Fit parameter of constituent quark massCan we put constrains on the constitute quark mass parameter ?

19

Constraints on the system evolution dynamics

Theoretical model for particle production at RHIC typically involve initial conditions, partonic evolutions, hadronization and hadronic evolutions.

Theoretical uncertainties due to hadronization scheme and hadronic evolution are major issues for quantitative description of properties of QCD medium created at RHIC. eg., the hadronic evolution process have been added to the hydrodynamic models as an afterburner and have been shown to significantly alter the spectra shapes

of ordinary hadrons[1]. [1] T. Hirano et al., Phys. Rev. C 77, 044909 (2008)

Can our derived quark distributions, representing a cumulative effect from initial conditions through partonic evolution, be used to det

ermine the final-state hadron momentum distribution?

20

Original version failed to reproduce the spectra data:

– Insufficiency parton cascading cross sections in the ZPC model where only pQCD processes have been included?

– Wrong choice of hadronization scheme?

Dynamical model calculation (1) A Multi-Phase Transport model[1]

– Initial condition: HIJING

– Partonic evolution: ZPC

– Hadronization: coalescence

– Hadronic evolution: ART

[1] Z.W. Lin et al., Phys. Rev. C 72, 064901 (2005)

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Modified version:

– Tuned the initial parton pT distribution inherited from HIJING string melting empirically, (vT0,Tth0);

– Requirement: the tuned distributions after parton cascade match our derived s/d quark dis;

– Coalescence scheme: two nearest (in coordinate space) quarks meson while three nearest quarks baryon.

Dynamical model calculation (2)

An essential ingredient in Reco./Coa. model calculation: the distribution of effective constituent quarks that readily turn into hadron.

It can faithfully reproduce the data at intermediate pT.

Summary

N()/N(K) vs. Npart rules out the K+K- coalescence as a dominant channel for production at RHIC;

N()/N() vs. pT favors the model prediction that s are made via thermalied s-quarks coalescence at RHIC;

N()/N() and N()/N() vs. pT/nq indicate the s-quark and d-quark have a similar KET distribution: partons have undergone a partonic evolution possibly described by hydrodynamics; the distribution of effective constituent quarks can reproduce the reasonable hyperon Pt distribution.

v2() vs. pT concludes that the partonic collectivity has been formed at RHIC;

Un-polarization signal of s-quark might imply that the system created at RHIC is isotropic to the extent that, locally, there is no longer a preferred direction. Again, favors the QGP scenario.

Since mesons are made via coalescence of seemingly thermalized s quarks in central Au+Au collisions, the observations imply hot and dense matter with partonic collectivity has been formed at RHIC.

23

All 120 TOF trays are installed at STAR and data will be taken in next RHIC runs

PID information for > 95% of kaons and protons in the STAR acceptance

Clean e± ID down to 0.2 GeV/c

/K separation to 1.6 GeV/c – 0.7 for TPC alone

(+K)/p to p = 3 GeV/c – 1.2 for TPC alone

Clean electron ID down

to 0.2 GeV

STAR-China Collaboration plan:120 trays of MRPC modules which leverage MRPC development at CERN (Crispin Williams et al) Development of HPTDC Chip STAR-MRPC TOFs are contributed from the China-STAR groupSTAR-MRPC TOFs are contributed from the China-STAR group

Fully complete in time for run 10 (fall 2009)Phi reconstruction from e+e-

TOF+TPC : one kaon from φ identified by TPC, the other by TOF TPC+TPC : the 2 kaons from φ identified using only TPC

24Y.G.Ma

RHIC low energy scan: the breaking of NCQ scaling of elliptic flow?

Violation of the NCQ scaling for the identified-particle elliptic flow may indicate the hadronic dominant phase is coming.

J. Tian, J. H. Chen, Y. G. Ma et. al., Phys. Rev. C 79, 067901 (2009)

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Di-hadron correlation in the AMPT model: Black: trigged by Black: trigged by or orΩΩ; ; Blue: trigged by any hadronBlue: trigged by any hadron

Away side: Phi/Omega-trigged correlation functions are narrower than the hadrons-trigged correlation function

it is consistent with the scenario of earlier freeze-out of phi/omega production

YGM, JPG 32(2006)S373, SQM06

Many Thanks for STAR collaborators, especially for Jinhui Chen, Guoliang Ma, Xiangzhou Cai, Huanzhong Huang, Nu Xu et al.

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Creation of the Hot Dense Matter under the extreme condition at RHIC heavy ion collisions

RHIC white paper: Nucl. Phys. A 757

RHIC creates hot and dense matter, parton loss energy when traverse the medium.

Away-side peak vanishes in Au-Au central collision@200GeV/c dense matter

Strong suppression of the High Pt meson Hot dense matter