Physical mechanism of the (tri)critical point generation

We discuss some ideas resulting from a phenomenological relation recently declared between the tension of string connecting the static quark-antiquark pair and surface tension of corresponding cylindrical bag. This relation analysis leads to the temperature of vanishing surface tension coefficient of the QGP bags at zero baryonic charge density as T_\sigma = 152.9 +- 4.5 MeV. We develop the view point that this temperature value is not a fortuitous coincidence with the temperature of (partial) chiral symmetry restoration as seen in the lattice QCD simulations. Besides, we argue that T_\sigma defines the QCD (tri)critical endpoint temperature and claim that a negative value of surface tension coefficient recently discovered is not a sole result, but should also exist in ordinary liquids at the supercritical temperatures.Comment: Talk given at the Conference "Critical Point and Onset of Deconfinement (CPOD)" that held on August 23 - 29, 2010, JINR, Dubna, Russia. Contains minimal change

Exactly Solvable Model for the QCD Tricritcal Endpoint

An inclusion of temperature and chemical potential dependent surface tension into the gas of quark-gluon bags model resolves a long standing problem of a unified description of the first and second order phase transition with the cross-over. The suggested model has an exact analytical solution and allows one to rigorously study the vicinity of the critical endpoint of the deconfinement phase transition. It is found that at the curve of a zero surface tension coefficient there must exist the surface induced phase tranition of the 2-nd or higher order. The present model predicts that the critical endpoint (CEP) of quantum chromodynamics is the tricritical endpoint.Comment: 14 pages, 3 figures, invited talk given at the International Workshop ``Relativistic Nuclear Physics: from Nuclotron to LHC Energies'', Kiev, Ukraine, June 18-22, 200

Quark Gluon Bags as Reggeons

The influence of the medium dependent finite width of QGP bags on their equation of state is analyzed within an exactly solvable model. It is argued that the large width of the QGP bags not only explains the observed deficit in the number of hadronic resonances, but also clarifies the reason why the heavy QGP bags cannot be directly observed as metastable states in a hadronic phase. The model allows us to estimate the minimal value of the width of QGP bags from a variety of the lattice QCD data and get that the minimal resonance width at zero temperature is about 600 MeV, whereas the minimal resonance width at the Hagedorn temperature is about 2000 MeV. As shown these estimates are almost insensitive to the number of the elementary degrees of freedom. The recent lattice QCD data are analyzed and it is found that besides sigma T**4 term the lattice QCD pressure contains T-linear and T**4 ln T terms in the range of temperatures between 240 MeV and 420 MeV. The presence of the last term in the pressure bears almost no effect on the width estimates. Our analysis shows that at hight temperatures the average mass and width of the QGP bags behave in accordance with the upper bound of the Regge trajectory asymptotics (the linear asymptotics), whereas at low temperatures they obey the lower bound of the Regge trajectory asymptotics (the square root one). Since the model explicitly contains the Hagedorn mass spectrum, it allows us to remove an existing contradiction between the finite number of hadronic Regge families and the Hagedorn idea of the exponentially growing mass spectrum of hadronic bags.Comment: One section removed, a few references added, the Regge trajectories of free QGP bags are considere

Exactly Solvable Models: The Road Towards a Rigorous Treatment of Phase Transitions in Finite Systems

We discuss exact analytical solutions of a variety of statistical models recently obtained for finite systems by a novel powerful mathematical method, the Laplace-Fourier transform. Among them are a constrained version of the statistical multifragmentation model, the Gas of Bags Model and the Hills and Dales Model of surface partition. Thus, the Laplace-Fourier transform allows one to study the nuclear matter equation of state, the equation of state of hadronic and quark gluon matter and surface partitions on the same footing. A complete analysis of the isobaric partition singularities of these models is done for finite systems. The developed formalism allows us, for the first time, to exactly define the finite volume analogs of gaseous, liquid and mixed phases of these models from the first principles of statistical mechanics and demonstrate the pitfalls of earlier works. The found solutions may be used for building up a new theoretical apparatus to rigorously study phase transitions in finite systems. The strategic directions of future research opened by these exact results are also discussed.Comment: Contribution to the ``World Consensus Initiative III, Texas A & M University, College Station, Texas, USA, February 11-17, 2005, 21

New Signals of Quark-Gluon-Hadron Mixed Phase Formation

Here we present several remarkable irregularities at chemical freeze-out which are found using an advanced version of the hadron resonance gas model. The most prominent of them are the sharp peak of the trace anomaly existing at chemical freeze-out at the center of mass energy 4.9 GeV and two sets of highly correlated quasi-plateaus in the collision energy dependence of the entropy per baryon, total pion number per baryon, and thermal pion number per baryon which we found at the center of mass energies 3.8-4.9 GeV and 7.6-10 GeV. The low energy set of quasi-plateaus was predicted a long time ago. On the basis of the generalized shock-adiabat model we demonstrate that the low energy correlated quasi-plateaus give evidence for the anomalous thermodynamic properties inside the quark-gluon-hadron mixed phase. It is also shown that the trace anomaly sharp peak at chemical freeze-out corresponds to the trace anomaly peak at the boundary between the mixed phase and quark gluon plasma. We argue that the high energy correlated quasi-plateaus may correspond to a second phase transition and discuss its possible origin and location. Besides we suggest two new observables which may serve as clear signals of these phase transformations.Comment: 14 pages, 4 figures, new signals of QGP formation are suggeste

Prompt muon contribution to the flux underwater

We present high energy spectra and zenith-angle distributions of the atmospheric muons computed for the depths of the locations of the underwater neutrino telescopes. We compare the calculations with the data obtained in the Baikal and the AMANDA muon experiments. The prompt muon contribution to the muon flux underwater due to recent perturbative QCD-based models of the charm production is expected to be observable at depths of the large underwater neutrino telescopes. This appears to be probable even at rather shallow depths (1-2 km), provided that the energy threshold for muon detection is raised above $\sim 100$ TeV.Comment: 7 pages, RevTeX, 7 eps figures, final version to be published in Phys.Rev.D; a few changes made in the text and the figures, an approximation formula for muon spectra at the sea level, the muon zenith-angle distribution table data and references adde