Quark-gluon plasma signatures in nucleus-nucleus collisions at CERN SPS

Two signatures of the quark-gluon plasma—strangeness ‘enhancement’ and J/ψ ‘suppression’—in nucleus-nucleus collisions at the SPS energies are critically discussed.     

Structural studies and T c dependence in La2−x Dy x Ca y Ba2Cu4+y O z type mixed oxide superconductors

A new series of mixed oxide superconductors with the stoichiometric composition La_2−x Dy _x Ca _y Ba₂Cu_4+y O _z (x=0.0 − 0.5, y=2x) has been studied for structural and superconductiong properties. Our earlier studies on La_2−x (Y/Er) _x Ca _y Ba₂Cu_4+y O _z series, show a strong dependence of T _c on hole concentration (p _sh). In the present work, the results of the analysis of the neutron diffraction measurements at room temprerature on x=0.3 and 0.5 samples are reported. It is interesting to know that Ca substitutes for both La and Ba site with concomitant displacement of La onto Ba site. Superconductivity studies show that maximum T _c is obtained for x=0.5, y=1.0 sample (T _c ∼ 75 K), for La_1.5Dy_0.5Ca₁Ba₂Cu₅O _z (La-2125).     

Two-fireball model of e+e− -annihilation into hadrons at high energies and the jet problem

Two-fireball model is proposed to describe the e⁺e^?-annihilation into hadrons. The jet problem and the scaling are discussed. The results obtained for one-particle inclusive distribution and some other characteristics are in quite good agreement with experimental data.     

Excluded volume effect for the nuclear matter equation of state

We present the thermodynamically consistent procedure to introduce the excluded volume effect into the equation of state of nuclear matter. Implications are discussed in the framework of a mean-field model for hadrons with eigenvolume.     

Quark-hadron three-phase mixture of baryonic matter

The phase diagrams of strongly interacting baryonic matter are constructed in a phenomenological model assuming three phases: hadrons, quarkgluon plasma and constituent quarks. Three-phase mixture states are considered in detail and it is shown that these states cover a finite area in the energy density-baryonic density plane. Possible hydrodynamic expansion processes involving the three-phase coexistence region in relativistic heavy-ion collisions are outlined.     

Rapidity dependence of thermal dileptons resulting from hadronizing quark-gluon matter with finite baryon charge

The influence of a non-vanishing baryon charge on the rapidity distribution of dileptons produced in ultrarelativistic heavy-ion collisions is studied. We employ a frozen motion model with scaling invariant expansion of the hadronizing quark-gluon plasma as well as a realistic rapidity distribution of secondary particles (i.e., pions and baryons) expected for RHIC energies. We demonstrate a sizeable suppression of the thermal dilepton yield at large rapidities due to the finite baryon density. This affects the most favorable rapidity window for using dileptons for the diagnostic of the quark-gluon plasma and the early temperature distribution of the hot reaction zone. To discriminate the thermal dileptons from Drell-Yan background we propose to utilize the dilepton yield scaled suitably by the pion multiplicity as function of rapidity.     

On a non-perturbative pressure effect in lattice QCD

We analyse Monte-Carlo data for the thermodynamical functions in lattice QCD. The linear in temperature non-perturbative contribution into the pressure of quark-gluon plasma is found.