12,912 research outputs found
Particle production in p-p collisions at sqrt(s) = 17 GeV within the statistical model
A thermal-model analysis of particle production of p-p collisions at sqrt(s)
= 17 GeV using the latest available data is presented. The sensitivity of model
parameters on data selections and model assumptions is studied. The system-size
dependence of thermal parameters and recent differences in the statistical
model analysis of p-p collisions at the super proton synchrotron (SPS) are
discussed. It is shown that the temperature and strangeness undersaturation
factor depend strongly on kaon yields which at present are still not well known
experimentally. It is conclude, that within the presently available data at the
SPS it is rather unlikely that the temperature in p-p collisions exceeds
significantly that expected in central collisions of heavy ions at the same
energy.Comment: 6 pages, 3 figures, submitted to Phys. Rev.
Statistical Model Predictions for p+p and Pb+Pb Collisions at LHC
Particle production in p+p and central Pb+Pb collisions at LHC is discussed
in the context of the statistical thermal model. For heavy-ion collisions,
predictions of various particle ratios are presented. The sensitivity of
several ratios on the temperature and the baryon chemical potential is studied
in detail, and some of them, which are particularly appropriate to determine
the chemical freeze-out point experimentally, are indicated. Considering
elementary interactions on the other hand, we focus on strangeness production
and its possible suppression. Extrapolating the thermal parameters to LHC
energy, we present predictions of the statistical model for particle yields in
p+p collisions. We quantify the strangeness suppression by the correlation
volume parameter and discuss its influence on particle production. We propose
observables that can provide deeper insight into the mechanism of strangeness
production and suppression at LHC.Comment: 7 pages, 5 figures, conference contribution to "International school
of nuclear physics", Erice, Sicily, 16 - 24 September 2008; Progress in
Particle and Nuclear Physics, 2009, in pres
Back Reaction of Hawking Radiation on Black Hole Geometry
We propose a model for the geometry of a dynamical spherical shell in which
the metric is asymptotically Schwarzschild, but deviates from Ricci-flatness in
a finite neighbourhood of the shell. Hence, the geometry corresponds to a
`hairy' black hole, with the hair originating on the shell. The metric is
regular for an infalling shell, but it bifurcates, leading to two disconnected
Schwarzschild-like spacetime geometries. The shell is interpreted as either
collapsing matter or as Hawking radiation, depending on whether or not the
shell is infalling or outgoing. In this model, the Hawking radiation results
from tunnelling between the two geometries. Using this model, the back reaction
correction from Hawking radiation is calculated.Comment: Latex file, 15 pages, 4 figures enclosed, uses eps
Reinventing spacetime on a dynamical hypersurface
In braneworld models, Space-Time-Matter and other Kaluza-Klein theories, our
spacetime is devised as a four-dimensional hypersurface {\it orthogonal} to the
extra dimension in a five-dimensional bulk. We show that the FRW line element
can be "reinvented" on a dynamical four-dimensional hypersurface, which is {\it
not} orthogonal to the extra dimension, without any internal contradiction.
This hypersurface is selected by the requirement of continuity of the metric
and depends explicitly on the evolution of the extra dimension. The main
difference between the "conventional" FRW, on an orthogonal hypersurface, and
the new one is that the later contains higher-dimensional modifications to the
regular matter density and pressure in 4D. We compare the evolution of the
spacetime in these two interpretations. We find that a wealth of "new" physics
can be derived from a five-dimensional metric if it is interpreted on a
dynamical (non-orthogonal) 4D hypersurface. In particular, in the context of a
well-known cosmological metric in , we construct a FRW model which is
consistent with the late accelerated expansion of the universe, while fitting
simultaneously the observational data for the deceleration parameter. The model
predicts an effective equation of state for the universe, which is consistent
with observations.Comment: References added to the Introduction, and Abstract modified. Accepted
for publication in Mod. Phys. Lett.
Statistical Model Predictions for Pb-Pb Collisions at LHC
The systematics of Statistical Model parameters extracted from heavy-ion
collisions at lower energies are exploited to extrapolate in the LHC regime.
Predictions of various particle ratios are presented and particle production in
central Pb-Pb collisions at LHC is discussed in the context of the Statistical
Model. The sensitivity of several ratios on the temperature and the baryon
chemical potential is studied in detail, and some of them, which are
particularly appropriate to determine the chemical freeze-out point
experimentally, are indicated. The impact of feed-down contributions from
resonances, especially to light hadrons, is illustrated.Comment: 5 pages, 2 figures, 1 table, SQM 2006 conference proceedings,
accepted for publication in J. Phys.
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