38,558 research outputs found
Centrality dependence of the multiplicity and transverse momentum distributions at RHIC and LHC and the percolation of strings
The dependence of the multiplicity and the transverse momentum distribution
on the number of collisions are studied for central and peripheral Au-Au
collisions at SPS, RHIC and LHC energies in the framework of percolation of
strings. A scaling law relating the multiplicity to the mean transverse
momentum is obtained. Our results are in overall agreement with the SPS and
RHIC data, obtaining a suppression on distribution even for larger
than 1 GeV/c.Comment: Contribution to QM2002, espcrc1.st
Cumulative particle production as a rare event
The generalization of the Glauber formula for cumulative production events is
derived. On its basis the multiplicity distribution in such events is related
to the one in the minimum bias events. As compared to the rare events of type
, the formula involves a shift in the arguments determined by the
multiplicity from a collision with a cluster of several nucleons.Comment: 11 pages, LaTe
Colour strings vs. hard pomeron in perturbative QCD
Average multiplicities and transverse momenta in AA collisions are studied in
the soft and hard regions, in fusing string and perturbative QCD scenarios
respectively. Striking similarities are found between the predictions of the
two approaches. Multiplicities per string and average p_t^2 are found to,
respectively, drop and rise with A in a very similar manner, so that their
product is nearly a constant. In both approaches total multiplicities grow as
A, that is as the number of participants. The high tail of the p_t distribution
is found to behave as A^1.1 in the perturbative QCD scenario.Comment: 10 pages, 8 figure
- dependence of the flow coefficients for pp collisions in the color string scenario. Monte-Carlo simulations
In the color string picture with fusion and percolation the dependence of the
flow coefficients on the transverse momentum is studied for pp collisions
the LHC energy respectively. Monte-Carlo simulations are used to locate simple
strings and their fused clusters. The results favorably agree with the CMS data
in the region GeV/c appropriate for the string scenario.Comment: 10 pages, 6 figures. arXiv admin note: text overlap with
arXiv:1407.459
coupling constant in light cone QCD sum rules
We employ the light cone QCD sum rules to calculate coupling
constant by studying the two point correlation function between the vacuum and
the pion state. Our result is consistent with the traditional QCD sum rules
calculations and it is in agreement with the experimental value.Comment: 8 pages, latex, 2 figure
Prospects for the Detection of the Deep Solar Meridional Circulation
We perform helioseismic holography to assess the noise in p-mode travel-time
shifts which would form the basis of inferences of large-scale flows throughout
the solar convection zone. We also derive the expected travel times from a
parameterized return (equatorward) flow component of the meridional circulation
at the base of the convection zone from forward models under the assumption of
the ray and Born approximations. From estimates of the signal-to-noise ratio
for measurements focused near the base of the convection zone, we conclude that
the helioseismic detection of the deep meridional flow including the return
component may not be possible using data spanning an interval less than a solar
cycle
Fusion of strings vs. percolation and the transition to the quark-gluon plasma
In most of the models of hadronic collisions the number of exchanged colour
strings grows with energy and atomic numbers of the projectile and target. At
high string densities interaction between them should melt them into the
quark-gluon plasma state. It is shown that under certain assumptions about the
the string interaction, a phase transition to the quark gluon plasma indeed
takes place in the system of many colour strings. It may be of the first or
second order (percolation), depending on the particular mechanism of the
interaction. The critical string density is about unity in both cases. The
critical density may have been already reached in central Pb-Pb collisions at
158 A GeV.Comment: 16 pages, 3 Postscript figure
String and Parton Percolation
A brief review to string and parton percolation is presented. After a short
introduction, the main consequences of percolation of color sources on the
following observables in A-A collisions: suppression, saturation of
the multiplicity, dependence on the centrality of the transverse momentum
fluctuations, Cronin effect and transverse momentum distributions, strength of
the two and three body Bose-Einstein correlations and forward-backward
multiplicity correlations, are presented. The behaviour of all of them can be
naturally explained by the clustering of color sources and the dependence of
the fluctuations of the number of these clusters on the density.Comment: 7 pages, 6 figures. Plenary talk given at Hard Probes 2004, Ericeira,
Portuga
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