1

Overview of Physics from China’s STAR-TOF Group

Yu-Gang MaShanghai Institute of Applied Physics, CAS

for the China-STAR Collaboration

• Introduction• Physics results: (1) PID spectra; (2)heavy quark; (3)Strange quark and Collectivity; (4) Simulation• Summary

Workshop on RHIC-STAR full TOF and related Physics,Hangzhou, China; April 27-29, 2009

High-energy Nuclear Collisions

Initial Condition - initial scatterings - baryon transfer - ET production - parton dof

System Evolves - parton interaction - parton/hadron expansion

Bulk Freeze-out - hadron dof - interactions stop

jets

J/D

K, K*pd, HBT

elliptic flow velliptic flow v22

radial radial flowflowTT

Q2

time

partonic scatterings?early thermalization?

TTCC

TTchch

TTfofo

IntroductionWhy STAR-TOF ?

Identified hadron spectra• freeze-out dynamics• hadronization mechanism• Heavy flavor

Identified particle correlations• Chemical and kinetic properties of in-medium jet associated spectra• Fluctuations and correlations • Heavy flavor

Lepton program• In-medium vector meson properties• Heavy flavor

TPC dE/dx for low momentum range: π/K 0.6 GeV/c proton/meson 1.0 GeV/c

TOF will extendmomentum range of PID !

PID

TPC alone PID range: pi/k ~0.6 GeV/c,

(pi,k)/p ~1.6GeV/c;

TOF “alone” PID range: pi/k ~1.6GeV/c,

(pi,k)/p ~ 3.0GeV/cm2 m2

TOF=110ps k p

TPC alone TOF “alone”

PID hadrons (TPC + TOF)

TPC

Relativistic rising of dE/dx

High pT

High performance of time resolution

Low & intermediate pT 2.5<pT<3.0

PID 0.15 - 4 GeV/c

PID up to 12 GeV/c

Electron identification

Combined with TOF ， electrons can be separated from pions cleanly

Electorns mixed with pions if only dE/dx of TPC is used to identify particles

X. Dong, Z.B. Xu, LJ Ruan, J Wu (USTC-BNL) et al

Lepton decay from heavy quarkLepton decay from heavy quark

PID hadron spectra

STAR Collaboration PRL 97 (2006) 152301

pT

Centrality dependence of , p pT spectra measured by TOF (red) and TPC-rdE/dx (black).

At 1.5<pT<7 GeV/c, RCP(p) > RCP() , RCP(p) shows obvious decreasing trend.

At 4<pT<12 GeV/c, both and p are strongly suppressed. They approach to each other at about 0.3

Curve:I. Vitev, PLB 639 (2006) 38.

particle ratios STAR Coll. PRL 97 (2006) 152301

1. -/+ are consistent with flat at unity in all pT, no significant centrality dependence.

2. pbar/p ratio: no significant centrality dependence, no sign of stronger gluon energy loss [ X.N. Wang, Phys Rev C 58 (1998) 2321 ].

• The p(pbar)/ ratios in Au+Au collisions show strong centrality dependence. In central Au+Au collisions, the p(pbar)/ ratios show an enhancement at intermediate pT range 2-4GeV/c.

• In general, parton energy loss models underpredict p/ ratios. No sign of stronger gluon energy loss.

R.J. Fries, et al., Phys. Rev. Lett. 90 202303 (2003); R. C. Hwa, et al., Phys. Rev. C 70, 024905 (2004);

DELPHI Collaboration, Eur. Phy. J. C 5, 585 (1998), Eur. Phy. J. C 17, 207 (2000).

)expdEdx

measuredEdxLog(Z

)( 33 HeHe

Light Nuclei

d3He

The 1st observation of negative v2 at RHIC

d v2 follows A scaling, 3He v2 shows some deviation, need more statistics=> coalescence model in nucleonic DOFB2 & sqrt(B3) are consistent

Strong centrality dependence

11

A

A VB

A

p

ppA

A

AA Pd

dNEB

PddNE

33

BW parameters:F. RetierePhys.Rev. C70 (2004) 044907

Flow scaling in low energiesnucleonic coalescence

Yan, YGM et al., arXiv:0711.0127; Chin. Phys. Lett. 24 (2007)3488; Phys. Lett. B 638 (2006) 50 Directed flow follows A-scaling (C(A)=(A+1)/2):

X. Zhang, Z. Xiao, H. Xu, preliminary analysis FOPI data (2009)

Ca+Ca @ 25AMeVFor v1,v2: C(A)=5/8(A+3/5)For v3,v4: C(A)=3(A=2/3)

STAR Preliminary

World data

180ps

256ps

STAR Preliminary

Observation of and @ RHICH3Λ H3

Λ

– 1st ever observation of an anti-hypernucleus in the world;– 1st new particle/state created by the RHIC facility.J. H. Chen, talk in QM2009; to be submitted to Sciences

Open charm in p+p and d+Au

Charm semi-leptonic decay measured by TPC + TOF.Cross section and spectra (prototype TOF) in Run3 p+p, d+Au Phys. Rev. Lett. 94 (2005) 062301

Open charm in Au+Au

Run 4 Au+Au collisionsD0 reconstructed through K, channel.Heavy flavor semi-leptonic decay to electrons.

TPC+TOF

TPCe

pK

|11/| < 0.03

Heavy flavor flow and energy loss

Tfo = 220 MeV (best fit) – freeze out earlier<t> = 0.23 (best fit), <0.42 (1-). favor moderate or small radial flow.-- dense medium, light flavor thermalization.

D0 STAR Preliminary

At high pT, strong suppression ~ 0.3 (light hadron level), seems stagnant to flavor.

See Y.F. Zhang’s talk for more details

15

Final spectra and cross sections

Full TOF improves (x5) charm hadronic reconstruction

Freeze-out/flow parameters and cross-sections are extracted from the combined fit.

Charm total cross section scales approximately with Nbin=> evidence of  charm production at initial stage.

Non-photonic electron and charged hadron correlations are sensitive to D and B contributions to non-photonic electrons.The preliminary data indicates at pT ~ 4-6 GeV/c the measured B contribution to non-photonic electrons is comparable to D contribution based on PYTHIA model. Our measurement of B/(B+D) provides a constraint to the FONLL prediction.

Study B and D Contributions to Non-photonic Electrons via Azimuthal Correlations between Non-Photonic Electrons and

Charged Hadrons

B

D

Strange quark dynamics:Why the φ-meson ?

The medium produced in HI collisions is very short-lived → we need probes which carry information from the early stage to find out about the medium constituents: The φ(s-sbar) is a clean probe from early time:

K+

K-

K-

K+

φ

φφ

K+K-

QGP

– Small σ for interactions with non-strange particles– Relatively long-lived (41 fm/c) → decays outside the

fireball– Previous measurements have ruled out K+K-

coalescence as φ production mechanism → info not “diluted” by hadronic phase

The φ can provide info on particle production mechanisms / medium constituents:– The φ is a meson but as heavy as Λ,p baryons

– Differentiate between mass-type or meson/baryon- type dependencies

The clean φ is a good probe to understand the strange quark properties, transverse momentum dis. or spin orientation…

Strange quark dynamics:φ-meson production and s-quark flow

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

– We argue that the constitute quark dis. reflects properties of the effective partonic degrees of freedom at hadronization;

– Our data indicate that s-quarks have a transverse momentum distribution flatter than that of u/d quarks consistent with hydrodynamic expansion in partonic phase prior to hadronization;

– The validity of our approach to explore quark transverse momentum dis. at hadronization has also been tested with independent particle ratios;

– Our approach in complement with the consistent quark number scaling in elliptic flow provides a means to measure quantitative quark properties at hadronization of bulk partonic matter

Phys. Rev. C 78, 034907 (2008)

S-quark pT distribution

– Our data are consistent with the un-polarized expectation of 1/3 and thus no evidence is found for the transfer of the orbital angular momentum of the colliding system to the vector meson spin;

– Our measurements constrain the possible size of polarization phenomena in the production dynamics of vector mesons.

Phys. Rev. C 77, 061902R (2008)

S-quark polarization?

See X.Z. Cai’s talk for more detail; also Q. Xu’s talk

Strange hadron v2

Left plot: larger v2/part indicates stronger flow in more central collisions.

Right plot: smaller v2/part in Cu+Cu than in Au+Au; no thermalizatoin in Cu+Cu.

Phys Rev C 77, 054901 (2008)

See Yan Lv’s talk for more details

STAR Preliminary

Conical emission or deflected jets, need 3-particle correlation?

Mediumaway

near

Deflected jets

away

near

Medium

Conical Emission

Shock wave searches in AA collisions Deflected jets or conical emission?

Two component approach: - Correlated to trigger (jets..)- Uncorrelated to trigger (except via anisotropic flow)Bkg normalization 3-particle ZYAM

Deflected jets

Conical Emission

Jet-medium interaction and hadron correlation

G. Ma et al.,: G. Ma et al.,: Phys Lett B 641, 362 (2006); Phys Lett B 647, 122 (2007); Phys. Rev. C 76, 014906 (2007); Nucl. Phys. A 783, 515 (2007)

. See G.L. Ma’s talk for new progress in tommorow

Physics results & Impacts Charm Cross section and spectra in p+p, d+Au, Phys. Rev. Lett. 94 (2005) 062301

• Identified baryon and meson distributions at large transverse momenta from Au+Au collisions at 200 GeV, Phys. Rev. Lett. 97 (2006) 152301

• Partonic flow and -meson production in Au+Au collisions at √sNN = 200 GeV ， B. I. Abelev et al. (STAR Collaboration) ， Phys. Rev. Lett. 99 (2007) 112301

• Pion, kaon, proton and anti-proton transverse momentum distributions from p +p and d +Au collisions at √sNN = 200 GeV, Phys. Lett. B 616 (2005) 8

• Identified hadron spectra at large transverse momentum in p + p and d + Au collisions at √sNN = 200 GeV, Phys Lett B 637 (2006) 161

• Spin alignment measurements of the K*0(892) and phi(1020) vector mesons in heavy ion collisions at √sNN =200 GeV, Phys. Rev. C 77 (2008) 061902(R)

• Centrality dependence of charged hadron and strange hadron elliptic flow from √sNN = 200 GeV Au+Au collisions, Phys. Rev. C 77 (2008) 054901

• Mass ， quark-number ， and dependence of the second and fourth flow harmonics in ultrarelativistic nucleus-nucleus collisions, Phys. Rev. C75 （ 2007 ） 054906

• Energy and system size dependence of \phi meson production in Cu+Cu and Au+Au collisions , Phys. Lett. B 673 (2009) 183

A few tens talks (plenary+parallel) presented in QM04, SQM04, QM05, SQM06, QM06, QM08, SQM08, QM09

>10 PhD theses, of those: 1 PhD (J.H. Fu/CCNU) won One Hundred Excellent PhD Thesis Award (2005); 1 PhD (X. Dong/USTC), won The Special Presidential Scholarship Award of CAS (2005) 3 PhD (G.L.Ma/SINAP, J. H. Chen/SINAP, Y. F. Zhang/USTC), won The Presidential Award of CAS (2006,2008)

Some theoretical work• Three-Particle Correlations from Strong Partonic Cascade in the AMPT model ， G. L. Ma, Y. G.

Ma, S. Zhang, X. Z. Cai, J. H. Chen, Z. J. He, H. Z. Huang, J. L. Long, W. Q. Shen, X. H. Shi, C. Zhong, J. X. Zuo, Phys. Letts. B 647 （ 2007 ） 122

• Di-hadron azimuthal correlation and Mach-like cone structure in parton/hadron transport model ，G. L. Ma, S. Zhang, Y. G. Ma, H. Z. Huang, X. Z. Cai, J. H. Chen, Z. J. He, J. L. Long, W. Q. Shen, X. H. Shi, J. X. Zuo ， Phys Lett B 641 (2006) 62

• Extract charm cross section from its semileptonic decay at RHIC ， H. D. Liu, Y.F. Zhang, C. Zhong, Z.B. Xu ， Phys.Lett.B 639 （ 2006 ） 441

• Transverse momentum and pseudorapidity dependences of Mach-like correlations for central Au+Au collisions at √sNN = 200 GeV ， S. Zhang, G. L. Ma, Y. G. Ma, et al. ， PHYS REV C 76, 014904 (2007)

• Elliptic flow of $\phi$ meson and strange quark collectivity at RHIC, J. H. Chen, Y. G. Ma, G. L. Ma, X. Z. Cai, Z. J. He, H. Z. Huang, J. L. Long, W. Q. Shen, C. Zhong, J. X. Zuo ， Phys. Rev. C 74 (2006) 064902

• Statistical interpretation of multiplicity distributions and forward-backward multiplicity correlations in relativistic heavy ion collisions, Jinghua Fu, PHYS REV C 77, 027902 (2008)

• Hadron Azimuthal Correlations and Mach-like Structures in a Partonic/Hadronic Transport Model ，G.L. Ma, S. Zhang, Y.G. Ma, X.Z. Cai, J.H. Chen, Z.J. He, H.Z. Huang, J.L. Long, W.Q. Shen, X.H. Shi, C. Zhong, J. X. Zuo, Nucl. Phys. A 783 (2007) 515

• Partonic effect on anisotropic flows of baryon for Au+Au at 62.4 and 200 GeV/c ， J. X. Zuo et al., Euro. Phys. J. C 55 (2008) 463

• Longitudinal broadening of near side jets due to parton cascade, G. L. Ma, S. Zhang, Y. G. Ma, X. Z. Cai, J. H. Chen, C. Zhong, Euro. Phys. J. C 57 (2008) 589

Summary TOF has good performance to identify charged particles. Greatly enhance the PID pT range combining with rdE/dx method.

Since one TOF tray installed at STAR in Run3, many important physics have been measured.

, proton spectra, RCP, particle ratios.

Light nuclei spectra, v2 and coalescence parameter BA.

and electron from heavy flavor semi-leptonic decays.

etc …

Other physics is also very exciting:

strange quark dynamics

hadron correlation and fluctuation..

Much exciting physics results are calling once the full barrel TOF detector will be installed in fall of 2009.

bright future….

Thanks NSFC, CAS, MoST & DOE for the supports of the TOF project.

Physics results expected Physics with Full Barrel TOF - IIIMeasurement Physics Goal

all particle v2,  especially increasing the efficiency for multi-strange particle v2  measurement

Fix the partonic collectivity parameters

Fluctuation/ correlation studies with PID Understand the nature of possible phase transition

Away-side jet fragmentation yields, spectra Search for Mach cone

Yields, spectra of high-mass resonances Map out most of the resonances (if it is not all) from RHIC

Unlike-particle (e.g., -) correlations Spatial and temporal distributions of hadron production

Charmed hadron flow and yield ratios Charm collectivity and thermalization of light quarks (u,d,s)

Heavy quark jets; D,B-meson spectra at high pTProbe partonic medium and understand the nature of parton interactions, i.e. parton energy loss

Inclusive lepton and di-lepton spectra and invariant mass distributions Study possible in-medium modification of hadrons.

e+e pair production in UPC Strong field QED effects

o longitudinal polarization correlations CP violation search

MRPC Status & Plans

StatusMRPC Standard production procedure setupQuality check measurements definedWeb Parameter Database installed

Particle id

System size and energy dependence of φ-meson production

Phys. Letts. B 673, 183 (2009)

The Npart normalized phi meson yields in nucleus-nucleus collisions are found to be enhanced relative to those from p+p collisions with a different trend compared to strange baryons. The enhancement observed in phi mesons ruled out, for the first time, the canonical suppression scenario for strangeness production in high energy nuclear collisions.

See X.Z. Cai’s talk for more detail

Parton cascade?

two-particle correlation

G. Ma, Y. Ma (SINAP) et al., PLB 641, 362 (2006);

PLB 647, 122 (2007)

• Both partonic and hadronics dynamics contribute to the Mach-cone;

• The parton cascade is essential to describe the experimental amplitude of Mach-cone structure

three-particle correlation

• Strong parton cascade can produce Mach-like wave in central Au+Au collisions

Heavy flavor physics

Strange quark dynamics

phenomenology

• Conical emission