705 research outputs found
Hadronic correlations above the chiral/deconfinement transition
The statistical bootstrap model is critically revised in order to include a
medium-dependent resonance width in it. We show that a thermodynamic model with
a vanishing width below the Hagedorn temperature T_H and a Hagedorn
spectrum-like width above T_H may not only eliminate the divergence of the
thermodynamic functions above T_H, but also gives a satisfactory description
the lattice quantum chromodynamics (QCD) data on the energy density above the
chiral/deconfinement transition as the main result of this contribution. This
model allows to explain the absence of heavy resonance contributions in the fit
of the experimentally measured particle ratios at SPS and RHIC energies.Comment: 9 pages, 2 figures, contribution to proceedings of NAPP 2003,
Dubrovnik, Croatia, 26-31 May, 200
Electromagnetic Structure Functions of Nucleons in the Region of Very Small X
A two component model describing the electromagnetic nucleon structure
functions in the low-x region, based on generalized vector dominance and color
dipole approaches is briefly described.Comment: 3 pages, 1 figure, Talk given at the 14th Lomonosov Conference,
Moscow, August 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 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
Surface Partition of Large Fragments
The surface partition of large fragments is derived analytically within a
simple statistical model by the Laplace-Fourier transformation method. In the
limit of small amplitude deformations, a suggested Hills and Dales Model
reproduces the leading term of the famous Fisher result for the surface entropy
with an accuracy of a few percent. The surface partition of finite fragments is
discussed as well.Comment: 4 pages, 1 figur
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