“Polarization studies as additional tool to search and study of the quark-gluon plasma”

S.S. Shimanskiy (VBLHE, JINR)

QGP’2000 at CERN

A common assessment of the collected data leads us to conclude that we now have compelling evidence that a new state of matter has indeed been created, at energy densities which had never been reached over appreciable volumes in laboratory experiments before and which exceed by more than a factor 20 that of normal nuclear matter. The new state of matter found in heavy ion collisions at the SPS features many of the characteristics of the theoretically predicted quark-gluon plasma.

TJH RHIC PAC 9/29-30, 2003 TJH RHIC PAC 9/29-30, 2003 • Conclusions About Matter at RHIC:

– The data on high pt suppression and correlations support the conclusion that we have produced a medium that:

• - is dense; (pQCD theory →many times cold nuclear matter density)• - is dissipative( very strongly interacting)

– We need to show that: • - dissipation and collective behavior occur at the partonic stage• - the system is deconfined and thermalized• - a transition occurs: can we turn the effects off ?

– We need:• - extended AuAu run needed to address several important probes that need large data sets ( e.g., pT-dependence of suppression; J/ψ, ϒ, open charm, heavy baryon / meson flow); also, species and energy scans to map the evolution of key observables• - more guidance from theory (!) particularly on what to expect from hadronic scenarios

QGP’2003 at BNL

How we can use SPIN to find thermalization?

QGP + SPIN

the the system system isisthermthermalizedalized

in the plasma restframe there is no preferred direction, no polarization

Paul Hoyer, Physics Letters B,v.187 (1987)162Particle polarization as a signal of plasma formation

“Heavy ion collisions leading to the formation of quark-gluon plasma are characterized by an isotropic distribution of the parton momenta in the plasma rest frame. We discuss the restrictions that this isotropy imposees on the polarizations of plasma-produced virtual photons, hyperons and hadronic resonances. “

Dileptons as an unique probes for QGP

• Haven’t strong interaction.

• Come out from all evolution stages.

CERES/NA45 data

Dileptons Anisotropies. How we can resolve sub processes using its?

NN-reactions

TRANSPARENCES

e+e- anisotropy (theory)

E.L. Bratkovskaya, O.V. Teryaev, V.D. Toneev from JINR

Phys. Lett. B 348 (1995) 283.

E.L. Bratkovskaya, O.V. Teryaev, V.D. Toneev + W. Cassing, U. Mosel, M. Schafer from Giessen

Phys. Lett. B 348 (1995) 325.

W. Cassing, E.L. Bratkovskaya

Physics Reports 308 (1999) 65-233.

GSI and more energies Bratkovskaya E.L. et al., Z. Phys. C 75, 119.126 (1997)

SPS energyBratkovskaya E.L. et al., Z. Phys. C 75, 119.126 (1997)

SPS energy II Rapp R., hep-ph/0201101

Completed Prototype 28 module MRPC TOF Tray installed in STAR Oct. ‘ 02 in place of existing central trigger barrel tray

NeighborCTB Tray

EMCRails

FEE

MRPC design developed at CERN, built in China

Prototype Tray Constructionat Rice University

28 MRPC Detectors;24 made atUSTC

70 ps, 2 meter path

Strong team including 6Chinese Institutions in place

The STAR Barrel TOF

MRPC Prototype

Open Charm and Resonances in central Au-Au collisionsOpen Charm and Resonances in central Au-Au collisions

pT (GeV/c)

FOM

Do All 4.6

Do 2-4 2.6

Do 4-6 2.0

Do >6 1.0

K*o 0-1 2.0

K*o 1-2 1.85

K*o 2-3 1.74

K*o 3-5 1.39

(1020) 0-2 5.0

(1020) 2-5 3.4

(1520) 0-1.6 11.4

FOM (figure of merit) = reduction FOM (figure of merit) = reduction in required data set by using TOF in required data set by using TOF PIDPID

TOF PID also reduces systematic TOF PID also reduces systematic errors from correlated back-errors from correlated back-ground due to misidentified ground due to misidentified particlesparticles

Certain measurements are Certain measurements are impossibleimpossible without TOF – unlike particle without TOF – unlike particle correlations (correlations (scale dependent scale dependent correlation studies (velocity vs correlation studies (velocity vs momentum correlations), exotic momentum correlations), exotic searches… searches…

Examples of Benefit of TOFExamples of Benefit of TOF

TOF + TPC electron TagTOF + TPC electron Tag

• Works well at low energy – Works well at low energy – complements calorimetercomplements calorimeter

• Gives access to vector meson Gives access to vector meson ((,,,,,J/,J/) e+e- decays) e+e- decays

• Thermal dileptonsThermal dileptons

• Single electron spectrumSingle electron spectrum

• D meson yield, flowD meson yield, flow

RHIC energy Rapp R., hep-ph/0201101

J/ polarization Ioffe B.L., hep-ph/0310343Dubna, SPIN 2003

What will be interesting for investigations ?

(Will need to compare pp and AA data, energy and impact

parameter dependences)

Thank you!