Some Physics Proposal from Barrel STAR-TOFL. Ruan QM04 X. Dong BNL Seminar For details: see Tai...

International CCAST Summer School and Workshop on QCD & RHIC Physics Yu-Gang MA 12004/8/9-14, CCAST, Beijing

Some Physics Proposal from Barrel STAR-TOF

Yu-Gang Ma

Shanghai Institute of Applied Physics,Chinese Academy of Sciences

(For Chinese STAR-TOF Collaboration)University of Sciences and Technology of China (USTC)

Tsinghua University Shanghai INstitute of Applied Physics (SINAP)

Central China Normal University (CCNU)Institute of Modern Physics (IMP)

Institute of High Energy Physics (IHEP)


outline

Physics Highlights from 1/120 Barrel TOFWhat can we expect for full STAR-TOF

some simulations for Full TOFPartonic collective dynamicsOpen charm productionResonance physicsSearch for Multi-strange Baryons

Summary


70


New technology (MRPC, first developed by CERN ALICE) for TOF:

• measurements, cheap, reliable• pion/Kaon separation is extended from 0.6GeV/cto more than 1.6GeV/c• proton/Kaon/pionseparation is extended from 1.1GeV/c to 3GeV/c•Thus cover wider range of (p,K,p) pT (pT spectra, pbar/p)

But only one tray used ( it is only 1/120 coverage of the Barrel TOF(– 0.5<eta<0.)

pK

π

π/K π/Kπ/K/p π/K/p


Physics Highlights of onePhysics Highlights of one--tray TOF:tray TOF:

1. 1. HadronHadron SpectraSpectra


Traditional Cronin Effect is not the whole story at RHIC

STAR d+Au from TOFr analysis (USTC+BNL+RICE)

Results on KS, Λ and φ will reach higher pT(SINAP+UCLA)


For details: see Lijuan Ruan’s Talk in Friday


Physics Highlights of onePhysics Highlights of one--tray TOF:tray TOF:

2. Heavy Flavor2. Heavy Flavor


Electron Identification

After PID (cuts in beta), electronsare clearly separated from other particles

Only using TPC dE/dx ID, the electron band crosses with others, which makes the electron ID complicated.

X. Dong, Z.B. Xu, LJ Ruan, J Wu et al


Bottom:Ratios of the inclusive electrons over the total back-grounds.signal excesses are visible with pT > 1 GeV/c.

The total photonic backgrounds are shown as solid lines.Dashed lines depict the various contributing sources. The fractions were derived from simulations.


Physics results II: Direct/semilepton Spectra

Combined fit forD0 and electrons

PYTHIA: MSEL = 1, CTEQ5M1

Good agreement between D0 and electrons spectra!

d+Au and p+p do not show significant nuclear effect

L. Ruan QM04X. Dong BNL Seminar For details: see Tai An’s Talk


With the full With the full coverage of TOFcoverage of TOF


STAR TPC + TOF (MC)STAR TPC + TOF (MC)

Central (top 10%) collisions

acceptance with TPC:π: ~ 60%K: ~ 60%p: ~ 50%

acceptance with TPC+TOF:> 95% for all particles

S/N for φ reconstruction willincrease by a factor of 5-10⇒ v2 measurement possible

Z. Liu, F. Liu, et al.


STAR TPC + TOFSTAR TPC + TOF1) TOF will increase V0

reconstruction efficiency. In the case of Ω, a factor of 5 – 10 increase expected in the region pT~ 3-5 GeV/c!

2) TOF will also help future D meson reconstruction –increasing S/N ratios, same way for other resonances. (D0 → K−π+)(D0-bar → K+π−)

3) In the case for φ, a factor of 5-10 increase in S/N ratio is expected. φ=>K + + K - (49.1%)

H. Long et al.


STAR TPC + TOFSTAR TPC + TOFΩ v2 measurements

For integrated Ω v2 : needs ~ few 106 MiniBias events. More events without TOF ⇒ Multi-years running.

pT dependence Ω v2:for <20% around pT ~ 5 GeV/c, needs ~ few 10th 106 MiniBiasevents with TOF⇒ almost impossible without TOF

STAR 200 GeV results:T = 0.45 GeVdN/dy = 0.64, sum of Ω- and Ω+

< v2 > ~ 8%all are usable events (1.5 -3 factor)


TOF and Λ Hyperon

1.1 1.11 1.12 1.130

100

200

)2

inv_mass ( GeV/c

Embedded Data:Λ reconstruction with and without PID information!A Factor of 3 !!

0

100

200

300

400

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Λ

TPC only

TPC + TOF barrel

pt (GeV/c)R

esco

nstr

ucte

d Λ

Yie

lds \T

ex2alk\2002\ST

AR

\TX

Sept02igures\lam

bda_eff.kumac//

( )Tmmf ttSB /exp −⋅∝Input spectrum:T = 350 MeV


A Critical Test for Recombination

Duke Group, PLB 587, 73 (2004)

Ω

φ

how about φ, Ω, D, J/Ψ v2(p⊥) ?

Need Full TOF for good efficience and statistics

jets

J/ψ, D

Ω

φ

Ξ

Λ

π, K, K*

∆, p

d, HBT

elliptic flow velliptic flow v22

radial flowradial flow ββTT

Q2

time

partonic scatterings?early thermalization?

TTCCTTchch

TTfofo


115M115M4>pT>6.

42M85M2>pT>4.

23M59MpT>2.

2.6M12MAll pT

With TOFWithout TOF

D0 Sensitivity in pT

V. Greco, C.M. Ko, R. Rapp, nucl-th/0312100

Heavy Quark Flow Effects?

Important Measurement: Open CharmTOF helps by a factor of ~5 (all PT)TOF + Active Pixel Sensitive: x8Other Open Charm States Possible only with TOF

Full Coverage needed


Time scale of resonance stateResonance K*(892) ρ(770) f0(980) φ(1020) ∆(1232) Λ(1520) Σ(1385)Decay channel K π π π π π K K ee p π p K Λ πBranching Ratio % ~100 ~100 dominant 49.2 0.3 >99 22.5 88.2Width [MeV] 50.7 150 40 to 100 4.46 ~120 15.6 35.8Life time [fm/c] 4 1.3 40 ~1.6 13 5.6

Resonance Parent PT(GeV/c) TPC+TOFK*0 0-1 2.0K*0 1-2 1.85K*0 2-3 1.74K*0 3-5 1.39______________________φ(1020) 0-2 5.0φ(1020) 2-5 3.42___________________________Λ(1520) 0-1.6 11.4

Chemical Freeze-out--- formation of hadrons

Kinetic Freeze-out--- Interaction ceases

Increasing factor for statistical significance of the signal


search for search for didi--omegaomegaZ.Y. Zhang et al., Phys. Rev. C 61, 065204 (2000); Phys. Rev. C66, 015205 (2002)3 body decay：

2 body decay：

A chrial SU(3) model and analyses of the symmetry properties of two-baryon systems, some features:

A deeply bound, Eb ~ 100MeV;A compact object, Rrms~0.63fm, <<Rdmay be six strange quark state rather than a di-baryon configuration

Phenomenological estimation (coalescence/statistical): yield 10-4_10--7/central Au-Au; Full barrel TOF ~ 100M central AuAu events needed.


Relativistic Heavy Ion Collisions & Full TOF related physics

1) Initial Condition - baryon transfer- ET production- partons dof- gluon dynamics

2) System Evolves- parton/hadron

expansion- QCD phaseQUARK-GLUON PLASMA?

3) Bulk Freeze-out- hadrons dof- interactions stop

Time

Q2: partonic collectivity? QGP?

Tools: • Transverse Flow• Elliptic Flow

Problem:• Flow is additive

Approach:• Probes “insensitive” to hadronic stage (φ,Ξ,Ω,D,J/Ψ)

S.Bass

Q3: Resonance Physics?Q4: Multi-strange baryons?

Q1: Open charm: gluon dynamics?

Also we are interested in Event-by-event fluctuation and HBT physics etc.


ConclusionConclusionIn order to know about the elliptic flow of φ ,Ω, D, J/Ψ, Full TOF is necessary for good efficiency and statistics.In order to improve the measurements of Open Charm, TOF helps by a factor of ~5 (all PT) and Full Coverage neededIn order to investigate the hadronic evolution dynamics, TOF increases important factor for statistical significance of the resonance production.TOF will significantly enhance the hyperondetection efficiency. RHIC provides a unique environment for possible production of multiply strange di-baryons.


The EndThe End

Thank you!Thank you!

Some Physics Proposal from Barrel STAR-TOFL. Ruan QM04 X. Dong BNL Seminar For details: see Tai...

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