33,868 research outputs found
Unitarity of the tree approximation to the Glauber AA amplitude for large A
The nucleus-nucleus Glauber amplitude in the tree approximation is studied
for heavy participant nuclei. It is shown that, contrary to previous published
results, it is not unitary for realistic values of nucleon-nucleon
cross-sections.Comment: 15 pages, 1 figure, 1 table. Submitted to Yad. Fi
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
Production of a gluon with the exchange of three reggeized gluons in the Lipatov effective action approach
In the Regge kinematics the amplitude for gluon production off three
scattering centers is found in the Lipatov effective action technique. The
vertex for gluon emission with the reggeon splitting in three reggeons is
calculated and its transversality is demonstrated. It is shown that in the sum
of all contributions terms containing principal value singularities are
cancelled and substituted by the standard Feynman poles. These results may be
used for calculation of the inclusive cross-section for gluon production on two
nucleons in the nucleus.Comment: 22 pages, 9 figures; submitted to Eur.Phys.Jour.
Fluctuations of the number of participants and binary collisions in AA interactions at fixed centrality in the Glauber approach
In the framework of the classical Glauber approach, the analytical
expressions for the variance of the number of wounded nucleons and binary
collisions in AA interactions at a given centrality are presented. Along with
the optical approximation term, they contain additional contact terms arising
only in the case of nucleus-nucleus collisions. The magnitude of the additional
contributions, e.g., for PbPb collisions at SPS energies, is larger than the
contribution of the optical approximation at some values of the impact
parameter. The sum of the additional contributions is in good agreement with
the results of independent Monte Carlo simulations of this process. Due to
these additional terms, the variance of the total number of participants for
peripheral PbPb collisions and the variance of the number of collisions at all
values of the impact parameter exceed several multiples of the Poisson
variances. The correlator between the numbers of participants in colliding
nuclei at fixed centrality is also analytically calculated.Comment: updated version; as published by Phys. Rev.
BELLE Data on the Form Factor: A Game Changer?
We extend our analysis of the form factor by including
a comparison with the new BELLE data. The necessity of new precision
measurements in a broad interval of momentum transfers is emphasized.Comment: 4 pages, 3 figures. Addendum to Phys. Rev. D 83, 054020 (2011
Diffractive scattering on the deuteron projectile in the NLO: triple interaction of reggeized gluons
High-mass diffractive production of protons on the deuteron target is studied
in the next-to-leading order (NLO) of the perturbative QCD in the BFKL
approach. The non-trivial part of the NLO contributions coming from the triple
interactions of the exchanged reggeons is considered. Analytic formulas are
presented and shown to be infrared free and so ready for practical calculation.Comment: 28 pages, 2 figures; to be published in Eur.Phys.Jour.
On the application of the effective action approach to amplitudes with reggeon splitting
Application of the effective action approach to amplitudes with loop
integration is studied for collisions on two and three centers with possible
gluon emission. A rule is formulated for the integration around pole
singularities in the induced vertices which brings the results in agreement
with the QCD. It is demonstrated that the amplitudes can be restored from the
purely transverse picture by introducing the standard Feynman propagators for
intermediate gluons and quarks.Comment: 16 pages, 9 figures; submitted to Eur.Phys.Jour.
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