Physics with identified particles at STAR

Lijuan Ruan QM2006, Shanghai, Nov. 14, 2006 1

Physics with identified particles at STAR

Outline:• STAR Detector configuration • Motivation -- What has been observed at RHIC -- What still needs to be addressed• Highlight results of identified particle physics from STAR -- Low pT: bulk property -- Intermediate pT: coalescence -- High pT: parton energy loss

• Summary

Lijuan Ruan for the STAR Collaboration (Lawrence Berkeley National Laboratory)


The STAR Detector

MagnetMagnet

CoilsCoils

Central Central TriggerTriggerBarrel Barrel (CTB)(CTB)

ZCalZCal

Time Time Projection Projection

ChamberChamber(TPC)(TPC)

Year 2000Year 2000

Barrel EM Cal Barrel EM Cal (BEMC)(BEMC)

Silicon Vertex Silicon Vertex Tracker (SVT)Tracker (SVT)Silicon Strip Silicon Strip Detector (SSD)Detector (SSD)

FTPCFTPCEndcap EM CalEndcap EM CalFPDFPD

TOFp, TOFrTOFp, TOFr

FPDFPD

Year 2001+Year 2001+

PMD

Large acceptance: 2 coverage at mid-rapidity

Future upgrade: Time of Flight, DAQ1000, Heavy Flavor Tracker, Muon Telescope DetectorFuture upgrade: Time of Flight, DAQ1000, Heavy Flavor Tracker, Muon Telescope Detector


The theory-experiment comparison suggests that central Au+Au collisions at RHIC produce dense, rapidly

thermalizing matter characterized by • Initial energy densities above the critical values predicted by lattice

QCD for establishment of a Quark-Gluon Plasma• Nearly ideal fluid flow, marked by constituent interactions of very short

mean free path, established most probably at a stage preceding hadron formation

• Opacity to jets

What has been observed at RHIC

STAR Collaboration, NPA 757,102 (2005)


What still needs to be addressed • EOS and thermalization

• Freeze out properties

• v2 scaling and baryon enhancement: coalescence

• Jet quenching: parton energy loss

• Energy dependence: testing model prediction (coalescence and jet quenching)

• Heavy flavor yields and flow: color screening and partonic collectivity.

• Thermometers: dilepton, photon

• heavy quarkonium species.

• Jet fragments tagged by a hard direct photon, a heavy flavor

• forward jet correlation: CGC

Energy and system size dependence of v2, fluctuation

Three particle correlation

K p at low pT, light nuclei production

Correlation and fluctuation

K*, , KS, Λ, , , , K, p v2 and RCP

Baryon/meson-charged hadron correlation

PID spectra at high pT Pbar and pion: Casimir factor

CA/CF=9/4 Charm and bottom: dead cone

Energy dependence of identified particle production

Topic in black color, see M. Calderon’s talk


Elliptic flow and its fluctuation

Consistent v2/ scaling for all energies and collision systems. S. Voloshin’s talk(2.4)

First measurement of v2 fluctuation.

v2/<v2> ~36% observed.

P. Sorensen’s talk(2.4)

central

peripheral


v1 measurement

v4/v22 measurement, see Y. Bai’s talk(2.4)

v1 depends on energy, not on system size. G. Wang’s talk(3.4)


STAR preliminary

0-12% 200 GeV Au+Au

Hard-soft correlations

1. Hard-soft: away-side spectra approaching the bulk.

2. Mach-cone shock waves: a fast thermalization mechanism through dispersing energy into collective modes of shock waves.

Mediumaway

near

deflected jets

away

near

Medium

mach cone

M. Horner’s talk(3.2)

STAR Collaboration, PRL 95,152301 (2005)



Two Analysis Approaches:• Cumulant Method

1) Unambiguous evidence for three particle correlations.

• Jet-Flowbackground Method

1) Within a model dependent analysis, evidence for conical emission in central Au+Au collisions

C. Pruneau ’s talk(1.3) J. Ulery’s poster(44)

pTtrig=3-4 GeV/c

pTassoc=1-2 GeV/c

off-

diag

onal

pro

ject

ion

d+Au

0-12% Au+Au

=(12)/2

Δ2

Δ1 Δ1

0-12% Au+Au: jet v2=0

Δ2


What still needs to be addressed

• EOS and thermalization









K*, , KS, Λ, , , , K, p v2 and RCP






Fluctuation and freeze-out dynamics at RHIC

Energy scan to map out the critical point by measuring K/, p/ fluctuation and identified particle spectra in the future.

S. Das’s poster(107)

STAR preliminary

STAR Preliminary

5% central10% centralMin-Bias

Kp thermal fit

A. Iordanova’s poster(04)

Tc

h (G

eV

)

μB (MeV)

STAR PreliminarySTAR preliminary

K/ fluctuation: similar in 62 and 200 GeV

Positive long range correlation observed B. Srivastava poster(101)


Soft physics measurements vs dNch/d

nucl-ex/0505014 Lisa et al.

Tkin,<pT>, HBT Radii are strongly correlated with (dNch/dη).

STAR Preliminary

A. Iordanova’s poster(04)

STAR Preliminary

D. Das’s poster(21)


New direction

imagingvs Abeam

HBT measurement

Systematics!: s, mT, A+A, pair PID: consistent, detailed map of space-momentum substructure

mT scaling for space momentum correlation

P. Chaloupka’s poster(106) R. Witt’s talk(3.1)

D. Das’s poster(21)

mT (GeV/c)

Rin

v (

fm)

STAR preliminary

Cu+Cucentral

Cu+Cuperipheral

STAR preliminary

Exotic systems!Shifts from non-id!

*(1530)


What still need to be addressed










K*, , KS, Λ, , , , K, p v2 and RCP






v2 of strangeness hadrons and nuclei in 200 GeV Au+Au collisions

Intermediate pT (0.7<pT/n<2GeV/c)

• KS K* Λ v2: follow NQ scaling.

• The centrality dependence of v2: similar to minbias.

• Heavy particle: d follows A scaling, 3He follows A scaling at low pT, maybe deviate at higher pTneed more statistics.S. Blyth’s talk ()(3.1)

H. Liu’s talk(3.4)

Y. Bai’s talk (KSΛ)(2.4) X. Dong’s poster (K*)(75)

STAR preliminarySTAR preliminary

STAR preliminary

0-80% Au+Au


-h correlations-h correlations

__ifif Ω: sss (φ ss) at intermediate pT come mostly from TTT (TT) No near side correlation! Not consistent with data.

Same-side yield ≠0:Omegas with pOmegas with pTT less less

than 4.5 GeV/c contain than 4.5 GeV/c contain non-thermal non-thermal s-quarks: made in jets? s-quarks: made in jets?

Λ - h correlations are similar

__ifif Ω: sss (φ ss) at intermediate pT come mostly from TTT (TT) No near side correlation! Not consistent with data.

Same-side yield ≠0:Omegas with pOmegas with pTT less less

than 4.5 GeV/c contain than 4.5 GeV/c contain non-thermal non-thermal s-quarks: made in jets? s-quarks: made in jets?

Λ - h correlations are similar

J. Bielcikova’s talk(3.1)

R. C. Hwa et al., nucl-th/0602024.


What still need to be addressed










K*, , KS, Λ, , , , K, p v2 and RCP






Gluon contribution factor to hadrons

1. q jets or g jets gluon jet contribution to protons is significantly larger than to pions at high pT in p+p collisions at RHIC; pbar/ < 0.1 from quark jet fragmentation at low beam energy . STAR Collaboration, PLB 637, 161 (2006).

2. From Kretzer fragmentation function, the g/q jet contribution is similar to AKK. S. Kretzer, PRD 62, 054001 (2000).

200 GeV p+p


Particle ratios in 200 GeV Au+Au

At pT>5 GeV/c at RHIC at 200 GeV:1. p(pbar)/ are larger than the ratios from quark jet.

2. Expectation: pbar/ (Au+Au) < pbar/ (d+Au, p+p). (X.N. Wang, PRC 58, 2321,

(1998))

3. p(pbar)/ (Au+Au) ~ p(pbar)/ (d+Au, p+p). new experimental phenomena R.J. Fries et al., PRC 68, 044902 (2003); R.C. Hwa et al., PRC 70, 024905 (2004); DELPHI Collaboration, Eur. Phy. J. C 5, 585 (1998), Eur. Phy. J. C 17, 207 (2000); W. Liu et al., nucl-th/0607047.

gluon jet

quark jet

quark jet

STAR Collaboration, PRL 97 (152301) 2006

B. Mohanty’s talk(2.2)


Energy dependence of RAA (RCP)

Steeper initial jet spectra ?Or Color charge dependence ?At same pT : ~ 3 difference in xT.Q. Wang and X.N. Wang, PRC 71, 014903 (2005)

At 1.5< pT < 6 GeV/c: RCP(p+pbar) > RCP()At pT>6 GeV/c, RCP(p+pbar) ~ RCP()Similar to 200 GeV Au+Au collisions.



Energy dependence of particle composition

system size dependence B. Mohanty’s talk(2.2)

In 62 and 200 GeV Au+Au collisions:

1. Λ/KS ratio: similar peak positions.2. p(pbar)/ ratios: similar shapes at pT>2 GeV/c.

STAR preliminary


Discussion: recombination/coalescence model

Differences between data and current models: • The p(pbar)/ ratios in energy dependence at pT>2 GeV/c. R.J. Fries et al., PRC 68, 044902 (2003).

• The Ω/Ф ratio at pT>4 GeV/c. R. C. Hwa et al., nucl-th/0602024.

• The Ω-h correlation with 2.5<pT(trigger)<4.5 GeV/c and 1.5<pT(associate)<pT(trigger) GeV/c. R. C. Hwa et al., nucl-th/0602024.

S. Blyth’s talk(3.1)


J. Bielcikova’s talk(3.1)

STAR preliminary


Summary

• EOS and thermalization: 1) Significant v2 fluctuation 2) 3 particle jet correlation: evidence

for conical emission.

• Coalescence 1) Similar shape of p(pbar)/ ratios at

pT>2 GeV/c between 62 and 200 GeV 2) The / ratio peaks at pT~4 GeV/c 3) Significant -h correlation at

intermediate pT.


The common suppression of pbar and pion new experimental phenomena



K p at low pT, light nuclei production Correlation and fluctuation

K*, , KS, Λ, , , , K, p v2 and RCP


PID spectra at high pT

Pbar and pion: Casimir factor CA/CF=9/4 Charm and bottom: dead cone


Thanks to the STAR Collaboration!


STAR QM2006 parallel talks• J.H. Chen --- Spin alignment of vector mesons (K*, ) in Au+Au and p+p collisions at 200 GeV.• H. Liu (3.4) --- Yields and elliptic flow of d(dbar) and 3He(anti-3He) in Au+Au collisions at 200 GeV.• G. Wang (3.4) --- Incident-energy and system-size dependence of directed flow.

• Y. Bai (2.4) --- v2, v4 centrality, pT and particle-type dependence in Au+Au collisions at RHIC

• I. Selyuzhenkov (3.4) --- Global polarization of Lambda hyperons in Au+Au collisions at RHIC

• S. Voloshin (2.4) --- Energy and system size dependence of elliptic flow and v2/ε scaling

• J. Putschke (1.3) --- Near-side correlations of high-pT hadrons from STAR

• B. Mohanty (2.2) --- Properties of particle production at large transverse momenta in Cu+Cu and Au+Au collisions at RHIC energies

• M. Horner (3.2) --- Low and intermediate pT azimuthal di-hadron correlations from 200 GeV Au+Au collisions measured in STAR

• J. Bielcikova (3.1) --- High pT azimuthal and pseudorapidity correlations with strange baryons and mesons at RHIC

• X. Lin (2.2) --- Study B and D contributions via azimuthal correlations between non-photonic electrons and charged hadrons• C. Zhong (2.1) --- Scaling of charm integrated cross section and modification of its transverse momentum spectra in d+Au and

Au+Au collisions at RHIC• R. Witt (3.1) --- 0(1530) production in heavy ion collisions and its implications for t(therm-chem)• S. Blyth (3.1) --- A measurement of the centrality dependence of the N()/N() ratio and anisotropic flow • P. Djawotho (3.1) --- Quarkonium production at STAR• S. Chattopadhyay (3.2) --- Azimuthal -charged hadron correlations in d+Au and p+p collisions from STAR at 200 GeV• M. Russcher (3.3) --- Direct photon production in p+p and d+Au collisions at 200 GeV from STAR• P. Sorensen (2.4) --- First measurements of elliptic flow fluctuations• C. Pruneau (1.3) --- Is there a Mach-cone? – Three particle azimuthal correlations from STAR• L. Molnar (1.1) --- Probing small-x gluons and large-x quarks: jet-like correlations between forward and mid-rapidity in p+p, d+Au and

Au+Au collisions at STAR• J. Wu (1.4) --- A barrel TOF for STAR at RHIC• A. Rose (1.4) --- A heavy flavor tracker for STAR


STAR QM2006 posters

• P. Chaloupka --- - correlations in d+Au and Au+Au collisions at STAR• S. Das --- Strangeness fluctuations at RHIC• T. Tarnowsky --- Energy and system size dependence study of percolation phase transition• R. Raniwala --- Elliptic flow of inclusive photons and charged particles in Cu+Cu collisions at 200 GeV• J. Ulery --- Are there Mach cones in heavy ion collisions? Three particle azimuthal correlations in STAR• J. Bouchet --- Performance studies of the silicon detectors in STAR towards microvertexing of rare decays.• M. Cosentino --- Upsilon measurement in STAR• A. Iordanova --- System size dependence of freeze-out properties at RHIC• D. Das --- Identical Meson Interferometry in STAR Experiment• X. Dong --- K* production in Au+Au collisions at RHIC• H. Gose --- Proton femtoscopy in STAR• A. Knospe --- Strangeness and heavy flavor production

• G. Lin --- The inclusive photon and charged particle v2 at 200 GeV in Au+Au and Cu+Cu collisions.

• R. Longacre --- scaled correlation signals which increase with centrality of Au+Au collisions at 200 GeV• T. Nayak --- Net charge fluctuations using high order cumulants• P. Netrakanti --- Mechanism of particle production in p+p and d+Au collisions• M. Shao --- A study of the intrinsic time resolution of MRPC used in STAR-TOF • S. Monika --- Energy and system size dependence of photon production• B. Srivastava --- Understanding the particle production mechanism with correlation studies using long and short

range correlations and the balance function• A. Timmins --- The centrality dependence of strange baryon and meson production in Cu+Cu and Au+Au relativistic

heavy ion collisions with 200 GeV


STAR Collaboration

U.S. Labs: Argonne, Lawrence Berkeley, and Brookhaven National Labs

U.S. Universities: UC Berkeley, UC Davis, UCLA, Caltech, Carnegie Mellon, Creighton, Illinois-Chicago, Indiana, Kent State, MIT, MSU, CCNY, Ohio State, Penn State, Purdue, Rice, Texas A&M, UT Austin, Washington, Wayne State, Valparaiso, Yale

Brazil: Universidade de Sao Paolo

China: IHEP - Beijing, IPP - Wuhan, USTC,Tsinghua, SINAP, IMP Lanzhou

Croatia: Zagreb University

Czech Republic: Nuclear Physics Institute

England: University of Birmingham

France: Institut de Recherches Subatomiques Strasbourg, SUBATECH - Nantes

Germany: Max Planck Institute – Munich University of Frankfurt

India:Bhubaneswar, Jammu, IIT-Mumbai, Panjab, Rajasthan, VECC

Korea:Pusan Nat’l University

Netherlands:NIKHEF

Poland:Warsaw University of Technology

Russia: MEPHI – Moscow, LPP/LHE JINR – Dubna, IHEP – Protvino

Thanks!

Physics with identified particles at STAR

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