289 research outputs found
Gluon shadowing in the Glauber-Gribov model at HERA
We calculate shadowing using new data on the gluon density of the Pomeron
recently measured with high precision at HERA. The calculations are made in a
Glauber-Gribov framework and Pomeron tree-diagrams are summed up within a
unitarity-conserving procedure. The total cross section of \vphot A
interaction is then found in a parameter-free description, employing gluon
diffractive and inclusive distribution functions as input. A strong shadowing
effect is obtained, in good agreement with several other models. Impact
parameter dependence of gluon shadowing is also presented.Comment: 18 pages, 6 figures; references added, discussion of model enlarged,
calculation of low-x contribution corrected; to appear in Phys. Let
Gluon shadowing and unitarity effects
New data from HERA experiment on deep inelastic scattering have been used to
parametrize nucleon and Pomeron structure functions. Within the Gribov theory,
the parameterizations were employed to calculate gluon shadowing for various
heavy ions. The latter was compared with predictions from other models.
Calculations of multiplicity reduction due to gluon shadowing for d+Au
collisions at forward rapidities at =200 GeV are in good agreement
with BRAHMS data on the nuclear modification factor.Comment: 5 pages, 4 figures, submitted to Acta Physica Hungarica A, Quark
Matter 2005 poster session proceedings; minor changes in the text adde
The Flow Constraint Influence on the Properties of Nuclear Matter Critical Endpoint
We propose a novel family of equations of state for symmetric nuclear matter
based on the induced surface tension concept for the hard-core repulsion. It is
shown that having only four adjustable parameters the suggested equations of
state can, simultaneously, reproduce not only the main properties of the
nuclear matter ground state, but the proton flow constraint up its maximal
particle number densities. Varying the model parameters we carefully examine
the range of values of incompressibility constant of normal nuclear matter and
its critical temperature which are consistent with the proton flow constraint.
This analysis allows us to show that the physically most justified value of
nuclear matter critical temperature is 15.5-18 MeV, the incompressibility
constant is 270-315 MeV and the hard-core radius of nucleons is less than 0.4
fm.Comment: 8 pages, 3 figure
Resolving the J/\psi RHIC puzzles at LHC
Experiments with gold-gold collisions at RHIC have revealed (i) stronger
suppression of charmonium production at forward rapidity than at midrapidity
and (ii) the similarity between the suppression degrees at RHIC and SPS
energies. To describe these findings we employ the model that includes nuclear
shadowing effects, calculated within the Glauber-Gribov theory,
rapidity-dependent absorptive mechanism, caused by energy-momentum
conservation, and dissociation and recombination of the charmonium due to
interaction with co-moving matter. The free parameters of the model are tuned
and fixed by comparison with experimental data at lower energies. A good
agreement with the RHIC results concerning the rapidity and centrality
distributions is obtained for both heavy Au+Au and light Cu+Cu colliding
system. For pA and A+A collisions at LHC the model predicts stronger
suppression of the charmonium and bottomonium yields in stark contrast to
thermal model predictions.Comment: SQM2008 proceedings, 6 page
2D String Theory as Normal Matrix Model
We show that the bosonic string theory at finite temperature has two
matrix-model realizations related by a kind of duality transformation. The
first realization is the standard one given by the compactified matrix quantum
mechanics in the inverted oscillator potential. The second realization, which
we derive here, is given by the normal matrix model. Both matrix models exhibit
the Toda integrable structure and are associated with two dual cycles (a
compact and a non-compact one) of a complex curve with the topology of a sphere
with two punctures. The equivalence of the two matrix models holds for an
arbitrary tachyon perturbation and in all orders in the string coupling
constant.Comment: lanlmac, 21 page
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