STAR @ Laboratory of Particle Physics, JINR

Present, Past and Futureactivities

Zulkarneev R.Ya.

Outline

➢ STAR Detector Overview➢ Past

✔ BEMC Creation ✔ Study of BEMC performances BEMC : Potentialities inherent

➢ Present current scientific programme & STAR White Paper

✔ Heavy Flavour Physics✔ Femtoscopy(HBT) group results✔ Soft Photon Physics Spin Physics✔ Software

➢ Future

STAR Detector overview

120 separate modules or 4800 towers: ∆φ,∆η = 0.05,0.05

LPP: BEMC Creation (1999-2004)

Barrel Electromagnetic Calorimeter (BEMC) hardware :

assembling of the modules design and construction of the PMT-boxes design and manufacture of the optical system

Total contribution of LPP STAR group in the BEMC creation was estimated in terms of money as much as US 931 K $

On January 2005 the Technical Advisory Committee of STAR collaboration has reviewed the BEMC Project and concludes that BEMC has met cost, scope, and schedule, and is

ready to operate.

BEMC : potentialities inherent

Hot & dense matter at RHICHot & dense matter at RHIC

Possibilities for search of new kind QGP signals through observation:

Gammas & Electrons J/ψ , Upsilon and other states

Proton Spin problemProton Spin problem

Access to investigate the unique processes with production of the

direct photons, Drell-Yan’s pairs, W- and Z-bosons

EMC adds a new triggering capabilities: high Pt , Jets , J/ψ,…

LPP:Study of BEMC performances (2001-2003)

QM2004 : “Performance of the STAR Barrel Electromagnetic Calorimeter”

Typical MIP spectrum

Eγ,e = (1.0 - 50) GeV

∆E/E ~ 0.16/√E GeV

η = [1;-1] φ = [0;2π]

The STAR Collaboration’s Critical Assessment of theEvidence from the RHIC Collisions (STAR White Paper, 14 January 2005)

What are the critical needs from future experiments?

...measure the nuclear modification factors for charmed meson production, to look for the prediction to reduce energy loss for heavy quarks…

…look for the extra suppression of charmonium compared to open charm…

…develop thermometers for early stage of collisions …well before chemical freezeout

…central AuAu-interactions at RHIC produce dence, rapidly thermalizing matter characterized by: 1) initial energy densities above the critical values predicted by lattice GCD for establishment of a QGP;2) nearly ideal fluid flow established most probably at a stage preceding hadron formation; and 3)opacity to jets. …We pose a set of important open questions, and suggest additional measurements…which should be addressed before there can be a compelling basis to conclude that we have definitively formed thermalized, deconfinement matter at RHIC.

I. Investigation of inclusive high PT non- photonic electron spectra in PP-, dAu- and AuAu- collisions at RHIC energies. Why high PT electron spectra?

Heavy Flavour States (HFS) are accessible through their b, c e + X leptonic channel decays. That is direct way to Heavy Flavour Physics study

II. Search of direct soft photons produced in dAu- and AuAu- collisions at 200GeV (Soft Photnos Physics)

The40-160 MeV photons are accessible at STAR TPC Do its serve as a kind of Thermometer for early stages of the matter producted at RHIC ? III. Study of two particle correlation functions in AuAu- collisions at RHIC

energies (HBT-femtometry technics).

IV. Study of transverse spin structure of the proton. (Spin physics)

LPP: Current Physics Programme

1. Investigation of high Pt non-photonic electron spectra in pp-, dA- and

AuAu- collisions at 200 GeV ∆Pt : (1.0 – 10.0)GeV ; BEMC , TPC and STAR triggering systems

∆ η : [1.0 , -1.0]

Goals: cross-sections of (cˉc)-, (b‾b)-states production;

info for HFS-triggering ; to look at the suppression of the heavy flavour states

producted in hot & dense matter ; J/ψ- production in long time prospect Physics Working Group : Heavy flavour Status: data analysis & publication of the first results

LPP: Heavy Flavour Physics

p + p

d + Au

200 GeV pp e + X σ(c¯ , c) µb = 1290 210 400 σ(b¯ , b) µb = 5.45±0.97±2.0

LPP:Heavy Flavor Physics

Heavy (c-,b-) quarks suppression:

• is theoretically more well controlled • measurement of it provides a critical

check of partonic energy loss nature

• Transition from hadronic to QGP is strong sensitive to number of active quark flavours and their mass

• provides reference data for studies of color screening via quarconium suppression in future

LPP: Heavy Flavor Physics (continuation)

a) inclusive electron ((e-+e+)/2) spectra for pp, dAu and AuAu collisions at √s

NN=200 GeV.

b)inclusive to background ratio for pp and 0-5% most central AuAu collisionsc) invariant e+e- mass spectrum

● Non-photonic electrons:➢ semileptonic charm & beauty decays➢ Drell-Yan processes

● Photonic electrons:➢ photon conversion, γ → e+e-

➢ π0 and η Dalitz decays, π0 →γe+e-

Non-photonic electron spectra for pp, dAu and AuAu collisions at √s

NN=200 GeV

LPP: Heavy Flavor Physics (continuation)

The modification factor, RAA

for dAu,

and AuAu collisions at √sNN

=200 GeV

➢ Strong suppression of non-photonic electrons has been observed in Au+Au, increasing with centrality

➢ RAA

~ 0.2-0.3 for pT > 3 GeV/c

➢ suggests large energy loss of heavy quarks !

to be published Phys.Rev.Lett.two person of LPP group are the principal authors of the publication!

LPP:Femtometry-HBT group results

II. Study of the correlation functions of “exsotic pair particles“

The LPP-France-Slovac-Czech Rep.group has been done the study of proton-lambda correlation in AuAu-collisions at RHIC

Being based on the known proton-lambda scattering lengths, the average size of the proton and lambda sources was found to be ~3 fm, close to the size of the proton source determined from proton-proton correlation function.

For proton-antilambda and antiproton-lambda systems, the correlation functions have been measured for the first time and the corresponding spin averaged scattering length was estimated.

A new perspective is open:

the correlation study of particle scattering in the systems

which can hardly be accessible by other nuclear means.

LPP: Soft Photon Physics

III. Search of the direct soft photons in dAu-,AuAu-collisions at 200GeV

∆Pγ : (40 – 160) MeV ; TPC and STAR triggering systems. ∆ηγ : [0.7 ,-0.7] Ultimate goal: tests for theoretical model predictions; receiving the data to estimate the temperature of thermalized stage(s) of the collision fireball; Physics Working Group : Spectra Status of the initial stage of work: studies of background - inclusive soft gamma spectra produced in AuAu-, dAu- collisions at 200 GeV - in progress

Pre-equilibrium Parton Cascade

EM & Weak Decayafter freeze-out

QGP Hadron Gas

PROMT DIRECT PHOTONS THERMAL DIRECT PHOTONS background PHOTONS

What does mean “DIRECT “PHOTONS

direct photons = AuAu-inclusive photons – T ( dAu-inclusive photons)

mainly hard gammas Eγ > 1 GeV

more soft gammas Eγ < 1GeV

Soft photons:theoretic predictions

there are a lot of model predictions for photon spectra in soft energy region thermal radiation sensitive : to initial state temperature; degrees of freedom and EOS; little interaction with surrounding matter But experimentally very challenging: large background of photons from hadron decays(neutral mesons)

LPP: Spin Physics

IV. The study of reactions:PP↑→ ( π+ , π -)+ X and PP → ( π+ , π - )+X at 200 GeV

A complete quark spin density matrix is given by three quark distributions :

f1 (x) -related with the longitudinal momentum quarks in nucleon; g1 (x) -related with helicity distribution in polarized nucleon and h1 (x) - related with transverse spin distribution (correlation between left- and right quarks ) in the transverse polarized nucleon. SPIN crisis can’t be resolve on compelling base without the h1(x) measurement Goal: observation of dependence of high Pt hadrons pair production plane on the incident proton beam polarisation in order to get transverse spin distribution in the proton (transversity) Status: proposal preparation in progress!

LPP: STAR Software Development

➢ NEOSTAR cluster ✔ STAR framework✔ Offline DB mirror

➢ STAR Database Browsers✔ STAR DB Browser✔ BEMC Browser✔ EEMC Browser

➢ STAR Content Management System✔ Drupal

➢ STAR GRID applications✔ Job Tracker (WS)✔ Job submission GUI✔ Log4c++, WS appender

BEMC, BSMD, EEMC database browser visualization

STAR Content Management System

Offline database browser

STAR collaboration has been using

th

is software since 2003

Future

➢ More Physics!

✔ J/Psi and oniums...✔ Direct Photons : more statistics and understanding of the background puzzle Participation in the STAR upgrade in order to enhance soft gamma photon efficiency registration, to extend energy interval up to 1 GeV PROPOSAL in PROGRESS✔ Spin Physics

➢ More Software!

✔ Grid Computing: Job Tracker Web Service✔ HEP Visualization