“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 system is thermalized  in the plasma rest frame there is no preferred direction, no polarization

Paul Hoyer, Physics Letters B,v.187 (1987)162 Particle 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)

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

SPS energy Bratkovskaya E.L. et al., Z. Phys. C 75, (1997)

SPS energy II Rapp R., hep-ph/

Completed Prototype 28 module MRPC TOF Tray installed in STAR Oct. ‘ 02 in place of existing central trigger barrel tray Neighbor CTB Tray EMC Rails FEE MRPC design developed at CERN, built in China Prototype Tray Construction at Rice University 28 MRPC Detectors; 24 made at USTC   70 ps, 2 meter path Strong team including 6 Chinese Institutions in place The STAR Barrel TOF MRPC Prototype

Open Charm and Resonances in central Au-Au collisions p T (GeV/c) FOM DoDo All4.6 DoDo DoDo DoDo >61.0 K* o K* o K* o K* o  (1020)  (1020)  (1520) FOM (figure of merit) = reduction in required data set by using TOF PID TOF PID also reduces systematic errors from correlated back- ground due to misidentified particles Certain measurements are impossible without TOF – unlike particle correlations (  scale dependent correlation studies (velocity vs momentum correlations), exotic searches… Examples of Benefit of TOF

TOF + TPC electron Tag Works well at low energy – complements calorimeterWorks well at low energy – complements calorimeter Gives access to vector meson ( , , ,J/  ) e+e- decaysGives access to vector meson ( , , ,J/  ) e+e- decays Thermal dileptonsThermal dileptons Single electron spectrumSingle electron spectrum D meson yield, flowD meson yield, flow

RHIC energy Rapp R., hep-ph/

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

What will be interesting for investigations ? (Will need to compare pp and AA data, energy and impact parameter dependences)

Thank you!