29 research outputs found
Predictions for dijet production in DIS using small x dynamics
We study the properties of dijet production in deep inelastic scattering
using a unified BFKL/DGLAP framework, which includes important subleading ln
(1/x) contributions. We calculate the azimuthal decorrelation between the jets.
We compute the cross section for dijet production as a function of Q^2 and the
jet transverse momentum, as well as calculate the total dijet rate. We compare
the predictions with HERA data.Comment: 7 pages, LaTeX with 4 eps figure
Deep inelastic scattering and "elastic" diffraction
We examine the total cross section of virtual photons on protons,
, at low and its
connection with ``elastic'' diffractive production in the two-gluon exchange dynamics for the virtual forward
Compton scattering amplitude. Solely based on the generic structure of
two-gluon exchange, we establish that the cross section is described by the
(imaginary part of the) amplitude for forward scattering of vector
states, . The
generalized vector dominance/color dipole picture (GVD/CDP) is accordingly
established to only rest on the two-gluon-exchange generic structure. This is
explicitly seen by the sum rules that allow one to directly relate the total
cross section to the cross section for elastic diffractive forward production,
, of vector states.Comment: 24 pages, latex file with three eps figures. BI-TP 2002/2
Wilson line correlator in the MV model: relating the glasma to deep inelastic scattering
In the color glass condensate framework the saturation scale measured in deep
inelastic scattering of high energy hadrons and nuclei can be determined from
the correlator of Wilson lines in the hadron wavefunction. These same Wilson
lines give the initial condition of the classical field computation of the
initial gluon multiplicity and energy density in a heavy ion collision. In this
paper the Wilson line correlator in both adjoint and fundamental
representations is computed using exactly the same numerical procedure that has
been used to calculate gluon production in a heavy ion collision. In particular
the discretization of the longitudinal coordinate has a large numerical effect
on the relation between the color charge density parameter g^2 mu and the
saturation scale Qs. Our result for this relation is Qs = 0.6 g^2 mu, which
results in the classical Yang-Mills value for the "gluon liberation
coefficient" c = 1.1.Comment: 8 pages, 10 figures, RevTEX4, V2: typo corrections, V3: small
clarifications, to be published in EPJ
Non-linear QCD dynamics in two-photon interactions at high energies
Perturbative QCD predicts that the growth of the gluon density at high
energies should saturate, forming a Color Glass Condensate (CGC), which is
described in mean field approximation by the Balitsky-Kovchegov (BK) equation.
In this paper we study the interactions at high energies and
estimate the main observables which will be probed at future linear colliders
using the color dipole picture. We discuss in detail the dipole - dipole cross
section and propose a new relation between this quantity and the dipole
scattering amplitude. The total ,
cross-sections and the real photon structure function are
calculated using the recent solution of the BK equation with running coupling
constant and the predictions are compared with those obtained using
phenomenological models for the dipole-dipole cross section and scattering
amplitude. We demonstrate that these models are able to describe the LEP data
at high energies, but predict a very different behavior for the observables at
higher energies. Therefore we conclude that the study of
interactions can be useful to constrain the QCD dynamics.Comment: 11 pages, 5 figures. Version to be published in European Physical
Journal
Cronin Effect and High-p_T Suppression in pA Collisions
We review the predictions of the theory of Color Glass Condensate for gluon
production cross section in p(d)A collisions. We demonstrate that at moderate
energies, when the gluon production cross section can be calculated in the
framework of McLerran-Venugopalan model, it has only partonic level Cronin
effect in it. At higher energies/rapidities corresponding to smaller values of
Bjorken x quantum evolution becomes important. The effect of quantum evolution
at higher energies/rapidities is to introduce suppression of high-p_T gluons
slightly decreasing the Cronin enhancement. At still higher energies/rapidities
quantum evolution leads to suppression of produced gluons at all values of p_T.Comment: 32 pages, 8 figures, v2: extended and improved discussion, references
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Nuclear DVCS at small-x using the color dipole phenomenology
Using the high energy color dipole formalism, we study the coherent and
incoherent nuclear DVCS process in the small-x regime. We consider simple
models for the elementary dipole-hadron scattering amplitude that captures main
features of the dependence on atomic number A, on energy and on momentum
transfer t. Using the obtained amplitudes we make predictions for the nuclear
DVCS cross section at photon level in the collider kinematics.Comment: 6 pages, 5 figures. Version to be published in European Physical
Journal
Odderon in Gauge/String Duality
At high energies, elastic hadronic cross sections, such as , are dominated by vacuum exchange, which in leading order of
the expansion has been identified as the BFKL Pomeron or its strong AdS
dual the closed string Reggeized graviton \cite{Brower:2006ea}. However the
difference of particle anti-particle cross sections are given by a so-called
Odderon, carrying C = -1 vacuum quantum numbers identified in weak coupling
with odd numbers of exchanged gluons. Here we show that in the dual description
the Odderon is the Reggeized Kalb-Ramond field () in the
Neveu-Schwartz sector of closed string theory. To first order in strong
coupling, the high energy contribution of Odderon is evaluated for Super Yang-Mills by a generalization of the gravity dual analysis for
Pomeron in Ref. \cite{Brower:2006ea}. The consequence of confinement on the
Odderon are estimated in the confining QCD-like hardwall model of
Polchinski and Strassler \cite{Polchinski:2001tt}.Comment: 69 pages, 6 figures. Title change to better reflect the content of
the paper. More discussion added in the Comments section. To be published in
JHE
DIS and the effects of fluctuations: a momentum space analysis
Among the dipole models of deep inelastic scattering at small values of the
Bjorken variable , one has been recently proposed which relates the virtual
photon-proton cross section to the dipole-proton forward scattering amplitude
in momentum space. The latter is parametrized by an expression which
interpolates between its behavior at saturation and the travelling wave,
ultraviolet, amplitudes predicted by perturbative QCD from the
Balitsky-Kovchegov equation. Inspired by recent developments in coordinate
space, we use this model to parametrize the proton structure function and
confront it to HERA data on deep inelastic scattering. Both event-by-event
and the physical amplitudes are considered, the latter used to investigate the
effect of gluon number fluctuations, beyond the mean-field approximation. We
conclude that fluctuations are not present in DIS at HERA energies.Comment: 9 pages, 2 figure
Critical Correlations of Wilson Lines in SU(3) and the High Energy Cross Section
We discuss deep inelastic scattering at high energies as a critical
phenomenon in 2+1 space - time dimensions. In the limit of Bjorken ,
SU(3) with quark fields becomes a critical theory with a diverging
correlation length where the
exponent is obtained from the center group Z(3) of SU(3). We
conjecture that the dipole wave function of the virtual photon for transverse
sizes obeys correlation scaling before exponentially decaying for distances larger than
the correlation length. Using this behavior combined with different
-independent dipole proton cross sections we calculate the proton structure
function and compare with the experimental data. We take the good agreement
with the measured proton structure function F as an indication that
at high energies dimensional reduction to an effective three dimensional theory
with a critical point occurs.Comment: 21 pages, 3 figure
Large mass Q-Qbar production from the Color Glass Condensate
We compute quark-antiquark pair production in the context of the Color Glass
Condensate model for central heavy-ion collisions. The calculation is performed
analytically to leading order in the density of hard sources present in the
projectiles, and is applicable to quarks with a mass large compared to the
saturation momentum. The formulas derived in this paper are compared to
expressions derived in the framework of collinearly factorized perturbative QCD
and in kt factorization models. We comment on the breaking of kt factorization
which occurs beyond leading order in our approach.Comment: 24 pages, 3 postscript figure