6,705 research outputs found
Large Rapidity Gap Processes in Proton-Nucleus Collisions
The cross sections for a variety of channels of proton-nucleus interaction
associated with large gaps in rapidity are calculated within the Glauber-Gribov
theory. We found inelastic shadowing corrections to be dramatically enhanced
for such events. We employ the light-cone dipole formalism which allows to
calculate the inelastic corrections to all orders of the multiple interaction.
Although Gribov corrections are known to make nuclear matter more transparent,
we demonstrate that in some instances they lead to an opaqueness. Numerical
calculations are performed for the energies of the HERA-B experiment, and the
RHIC-LHC colliders.Comment: 19 page
Nuclear Transparency to Intermediate-Energy Protons
Nuclear transparency in the (e,e'p) reaction for 135 < Tp < 800 MeV is
investigated using the distorted wave approximation. Calculations using
density-dependent effective interactions are compared with phenomenological
optical potentials. Nuclear transparency is well correlated with proton
absorption and neutron total cross sections. For Tp < 300 MeV there is
considerable sensitivity to the choice of optical model, with the empirical
effective interaction providing the best agreement with transparency data. For
Tp > 300 MeV there is much less difference between optical models, but the
calculations substantially underpredict transparency data and the discrepancy
increases with A. The differences between Glauber and optical model
calculations are related to their respective definitions of the semi-inclusive
cross section. By using a more inclusive summation over final states the
Glauber model emphasizes nucleon-nucleon inelasticity, whereas with a more
restrictive summation the optical model emphasizes nucleon-nucleus
inelasticity; experimental definitions of the semi-inclusive cross section lie
between these extremes.Comment: uuencoded gz-compressed tar file containing revtex and bbl files and
5 postscript figures, totalling 31 pages. Uses psfi
A linked cluster expansion for the calculation of the semi-inclusive A(e,e'p)X processes using correlated Glauber wave functions
The distorted one-body mixed density matrix, which is the basic nuclear
quantity appearing in the definition of the cross section for the
semi-inclusive A(e,e'p)X processes, is calculated within a linked-cluster
expansion based upon correlated wave functions and the Glauber multiple
scattering theory to take into account the final state interaction of the
ejected nucleon. The nuclear transparency for 16O and 40Ca is calculated using
realistic central and non-central correlations and the important role played by
the latter is illustrated.Comment: 18 pages, RevTeX, 3 ps figures. Final version, to appear in Phys.
Rev.
Diffraction in QCD
This lecture presents a short review of the main features of diffractive
processes and QCD inspired models. It includes the following topics: (1)
Quantum mechanics of diffraction: general properties; (2) Color dipole
description of diffraction; (3) Color transparency; (4) Soft diffraction in
hard reactions: DIS, Drell-Yan, Higgs production; (5) Why Pomerons interact
weakly; (6) Small gluonic spots in the proton; (7) Diffraction near the
unitarity bound: the Goulianos-Schlein "puzzle"; (8) Diffraction on nuclei:
diffractive Color Glass; (9) CGC and gluon shadowing.Comment: Based on the lecture given by B.K. at I LAWHEP, Porto Alegre, Brazil,
December 1-3, 200
Saturation Physics in Ultra High Energy Cosmic Rays: Heavy Quark Production
In this work we estimate the heavy quark production in the interaction of
ultra high energy cosmic rays in the atmosphere, considering that the primary
cosmic ray is a proton or a photon. At these energies the saturation momentum
Q_{sat}^2 stays above the hard scale \mu_c^2=4m_c^2, implying charm production
probing the saturation regime. In particular, we show that the ep HERA data
presents a scaling on \tau_c = (Q^2+\mu_c^2)/Q_{sat}^2. We derive our results
considering the dipole picture and the Color Glass Condensate formalism, which
one shows to be able to describe the heavy quark production in photon-proton
and proton-proton collisions. Nuclear effects are considered in computation of
cross sections for scattering on air nuclei. Implications on the flux of prompt
leptons at the earth are analyzed and a large suppression is predicted.Comment: 18 pages, 10 figures, 2 tables. Version to be published in JHE
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