29,385 research outputs found
Gluon saturation effects on J/Psi production in heavy ion collisions
We consider a novel mechanism for J/Psi production in nuclear collisions
arising due to the high density of gluons. We calculate the resulting J/Psi
production cross section as a function of rapidity and centrality. We evaluate
the nuclear modification factor and show that the rapidity distribution of the
produced J/Psi's is significantly more narrow in AA collisions due to the gluon
saturation effects. Our results indicate that gluon saturation in the colliding
nuclei is a significant source of J/Psi suppression that can be disentangled
from the quark-gluon plasma effects.Comment: 5 pages, 3 figures; v2: typos corrected; presentation improve
Diffractive dissociation and saturation scale from non-linear evolution in high energy DIS
This paper presents the first numerical solution to the non-linear evolution
equation for diffractive dissociation processes in deep inelastic scattering.
It is shown that the solution depends on one scaling variable , where is the saturation scale for the diffraction
processes. The dependence of the saturation scale on both
and is investigated, ( is a minimal rapidity gap for
the diffraction process). The - dependence of turns out to be the
same as of the saturation scale in the total inclusive DIS cross section. In
our calculations reveals only mild dependence on . The
scaling is shown to hold for but is violated at .Comment: 13 pages, 9 figure
D-instantons and multiparticle production in N=4 SYM
N=4 Super-symmetric Yang-Mills theory (N=4 SYM) in the strong coupling regime
has been successfully applied (through the AdS/CFT correspondence) to the
description of strongly coupled plasma which is a multiparticle state. Yet, the
high-energy scattering in the strong coupling limit of N=4 SYM is purely
elastic, so this multiparticle final state can never be produced: this is
because in this limit the theory is dual to weak supergravity, and the dominant
interaction is the elastic graviton exchange. Here we propose a resolution of
this dilemma by considering the contribution of D-instantons in bulk
space to the scattering amplitude. We argue that D-instantons coupled to
dilatons and axions are responsible for multiparticle production in strongly
coupled N=4 SYM, and the corresponding cross section increases with energy. We
evaluate the intercept and the slope of the corresponding Pomeron trajectory in
terms of the typical size of the D-instanton, and argue that the resulting
physical picture may resemble the real world.Comment: 22 pp and 11 figures in the eps forma
A Quantitative Investigation of the Pomeron
A comparative investigation of various Pomeron models is carried out through
the study of their predicted values of , B, and
in high energy pp and p scattering.
Our results strongly support a picture of the Pomeron in which we have both
moderate blackening and expansion of the p() - p amplitude in impact
parameter space as a function of energy in the ISR-SSC domain. In particular,
we obtain an excellent reproduction of the data with a hybrid eikonal model
which combines the hard Lipatov-like QCD Pomeron with the old fashioned soft
Pomeron and Regge terms. Our analysis shows that the additive quark model, at
least in the naive form, is not compatible with the data.Comment: pages 15, Late
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