23,050 research outputs found
Transverse momentum distributions and their forward- backward correlations in the percolating colour string approach
The forward-backward correlations in the distributions, which present a
clear signature of non-linear effects in particle production, are studied in
the model of percolating colour strings. Quantitative predictions are given for
these correlations at SPS, RHIC and LHC energies. Interaction of strings also
naturally explains the flattening of distributions and increase of
with energy and atomic number for nuclear collisionsComment: 6 pages in LaTex, 3 figures in Postscrip
Exact Study of the Effect of Level Statistics in Ultrasmall Superconducting Grains
The reduced BCS model that is commonly used for ultrasmall superconducting
grains has an exact solution worked out long ago by Richardson in the context
of nuclear physics. We use it to check the quality of previous treatments of
this model, and to investigate the effect of level statistics on pairing
correlations. We find that the ground state energies are on average somewhat
lower for systems with non-uniform than uniform level spacings, but both have
an equally smooth crossover from the bulk to the few-electron regime. In the
latter, statistical fluctuations in ground state energies strongly depend on
the grain's electron number parity.Comment: 4 pages, 3 eps figs, RevTe
Heavy quark(onium) at LHC: the statistical hadronization case
We discuss the production of charmonium in nuclear collisions within the
framework of the statistical hadronization model. We demonstrate that the model
reproduces very well the availble data at RHIC. We provide predictions for the
LHC energy where, dependently on the charm production cross section, a
dramatically different behaviour of charmonium production as a function of
centrality might be expected. We discuss also the case in elementary
collisions, where clearly the statistical model does not reproduce the
measurements.Comment: 8 pages, 5 figures; proceeding of SQM09, Buzios, Brazil, to be
published in J. Phys.
Resolving the plasma profile via differential single inclusive suppression
The ability of experimental signatures to resolve the spatio-temporal profile
of an expanding quark gluon plasma is studied. In particular, the single
inclusive suppression of high momentum hadrons versus the centrality of a
heavy-ion collision and with respect to the reaction plane in non-central
collisions is critically examined. Calculations are performed in the higher
twist formalism for the modification of the fragmentation functions. Radically
different nuclear geometries are used. The influence of different initial gluon
distributions as well as different temporal evolution scenarios on the single
inclusive suppression of high momentum pions are outlined. It is demonstrated
that the modification versus the reaction plane is quite sensitive to the
initial spatial density. Such sensitivity remains even in the presence of a
strong elliptic flow.Comment: 5 pages, 4 figures, RevTex
The canonical partition function for relativistic hadron gases
Particle production in high-energy collisions is often addressed within the
framework of the thermal (statistical) model. We present a method to calculate
the canonical partition function for the hadron resonance gas with exact
conservation of the baryon number, strangeness, electric charge, charmness and
bottomness. We derive an analytical expression for the partition function which
is represented as series of Bessel functions. Our results can be used directly
to analyze particle production yields in elementary and in heavy ion
collisions. We also quantify the importance of quantum statistics in the
calculations of the light particle multiplicities in the canonical thermal
model of the hadron resonance gas.Comment: 10 pages, 2 figures; submitted for publication in EPJ
Solitonic-exchange mechanism of surface~diffusion
We study surface diffusion in the framework of a generalized
Frenkel-Kontorova model with a nonconvex transverse degree of freedom. The
model describes a lattice of atoms with a given concentration interacting by
Morse-type forces, the lattice being subjected to a two-dimensional substrate
potential which is periodic in one direction and nonconvex (Morse) in the
transverse direction. The results are used to describe the complicated
exchange-mediated diffusion mechanism recently observed in MD simulations [J.E.
Black and Zeng-Ju Tian, Phys. Rev. Lett. {\bf 71}, 2445-2448(1993)].Comment: 22 Revtex pages, 9 figures to appear in Phys. Rev.
AAT/WFI observations of the Extragalactic H I Cloud HIPASS J1712-64
AAT/WFI optical images of a candidate extragalactic HI cloud, HIPASS
J1712-64, are presented. The g and r-band CCD mosaic camera frames were
processed using a new data pipeline recently installed at the AAO. The
resultant stacked images reach significantly deeper levels than those of
previous published optical imaging of this candidate, providing a detection
limit M_g -7 at a distance of 3Mpc, the inferred distance to HIPASS J1712-64.
However, detailed analysis of the images fails to uncover any stellar
population associated with the HI emission. If this system is a member of the
Local Group then it is pathologically different to other members. Hence, our
observations reinforce earlier suggestions that this HI cloud is most likely
Galactic in origin and not a Local Volume dwarf galaxy.Comment: 8 pages, accepted for publication in PASA (Figures reduced in
resolution, please contact gfl if you wish the higher resolution versions
Predictions of hadron abundances in pp collisions at the LHC
Based on the statistical hadronization model, we obtain quantitative
predictions for the relative abundances of hadron species in pp collisions at
the LHC. By using the parameters of the model determined at sqrt s = 200 GeV,
and extrapolating the overall normalization from ppbar collisions at the SPS
and Tevatron, we find that the expected rapidity densities are almost
grand-canonical. Therefore, at LHC the ratios between different species become
essentially energy-independent, provided that the hadronization temperature T_H
and the strangeness suppression factor gamma_S retain the stable values
observed in the presently explored range of pp and ppbar collisions.Comment: 4 pages. Final version published in JP
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