110 research outputs found
Generalized parton distributions in the deuteron
We introduce generalized quark and gluon distributions in the deuteron, which
can be measured in exclusive processes like deeply virtual Compton scattering
and meson electroproduction. We discuss the basic properties of these
distributions, and point out how they probe the interplay of nucleon and parton
degrees of freedom in the deuteron wave function
Survival probability of large rapidity gaps in QCD and N=4 SYM motivated model
In this paper we present a self consistent theoretical approach for the
calculation of the Survival Probability for central dijet production . These
calculations are performed in a model of high energy soft interactions based on
two ingredients:(i) the results of N=4 SYM, which at the moment is the only
theory that is able to deal with a large coupling constant; and (ii) the
required matching with high energy QCD. Assuming, in accordance with these
prerequisites, that soft Pomeron intercept is rather large and the slope of the
Pomeron trajectory is equal to zero, we derive analytical formulae that sum
both enhanced and semi-enhanced diagrams for elastic and diffractive
amplitudes. Using parameters obtained from a fit to the available experimental
data, we calculate the Survival Probability for central dijet production at
energies accessible at the LHC. The results presented here which include the
contribution of semi-enhanced and net diagrams, are considerably larger than
our previous estimates.Comment: 11 pages, 10 pictures in .eps file
Comments on two papers by Kapusta and Wong
We critically examine recently published results on the thermal production of
massive vector bosons in a quark-gluon plasma. We claim the production rate is
a collinear safe observable.Comment: 6 pages LATEX documen
Wide-angle elastic scattering and color randomization
Baryon-baryon elastic scattering is considered in the independent scattering
(Landshoff) mechanism. It is suggested that for scattering at moderate
energies, direct and interchange quark channels contribute with equal color
coefficients because the quark color is randomized by soft gluon exchange
during the hadronization stage. With this assumption, it is shown that the
ratio of cross sections at CM angle
decreases from a high energy value of R_{\pbar p / pp} \approx 1/2.7, down to
R_{\pbar p / pp} \approx 1/28, compatible with experimental data at moderate
energies. This sizable fall in the ratio seems to be characteristic of the
Landshoff mechanism, in which changes at the quark level have a strong effect
precisely because the hadronic process occurs via multiple quark scatterings.
The effect of color randomization on the angular distribution of proton-proton
elastic scattering and the cross section ratio is also discussed.Comment: 18 pages, latex2e, 4 uuencoded figures, include
Multiple-Scattering Series For Color Transparency
Color transparency CT depends on the formation of a wavepacket of small
spatial extent. It is useful to interpret experimental searches for CT with a
multiple scattering scattering series based on wavepacket-nucleon scattering
instead of the standard one using nucleon-nucleon scattering. We develop
several new techniques which are valid for differing ranges of energy. These
techniques are applied to verify some early approximations; study new forms of
the wave-packet-nucleon interaction; examine effects of treating wave packets
of non-zero size; and predict the production of 's in electron scattering
experiments.Comment: 26 pages, U.Wa. preprint 40427-23-N9
Annihilation of and through -meson intermediate state
The s-channel annihilation of proton and antiproton into a neutral pion and a
real or virtual photon followed by lepton pair emission is studied. Such
mechanism is expected to play a role at moderate values of the total energy
, when the pion is emitted around in the center of mass.
A fair comparison with the existing data is obtained taking into account
scattering and annihilation channels. The cross section is calculated and
numerical results are given in the kinematical range accessible in the PANDA
experiment at FAIR.Comment: 22 pages, 9 figures- Given more details on the model- final version
accepted for publicatio
A Large Hadron Electron Collider at CERN
This document provides a brief overview of the recently published report on
the design of the Large Hadron Electron Collider (LHeC), which comprises its
physics programme, accelerator physics, technology and main detector concepts.
The LHeC exploits and develops challenging, though principally existing,
accelerator and detector technologies. This summary is complemented by brief
illustrations of some of the highlights of the physics programme, which relies
on a vastly extended kinematic range, luminosity and unprecedented precision in
deep inelastic scattering. Illustrations are provided regarding high precision
QCD, new physics (Higgs, SUSY) and electron-ion physics. The LHeC is designed
to run synchronously with the LHC in the twenties and to achieve an integrated
luminosity of O(100) fb. It will become the cleanest high resolution
microscope of mankind and will substantially extend as well as complement the
investigation of the physics of the TeV energy scale, which has been enabled by
the LHC
Measurements of the Electron-Helicity Dependent Cross Sections of Deeply Virtual Compton Scattering with CEBAF at 12 GeV
We propose precision measurements of the helicity-dependent and helicity independent cross sections for the ep->epg reaction in Deeply Virtual Compton Scattering (DVCS) kinematics. DVCS scaling is obtained in the limits Q^2>>Lambda_{QCD}^2, x_Bj fixed, and -\Delta^2=-(q-q')^22 GeV^2, W>2 GeV, and -\Delta^21 GeV^2. We will use our successful technique from the 5.75 GeV Hall A DVCS experiment (E00-110). With polarized 6.6, 8.8, and 11 GeV beams incident on the liquid hydrogen target, we will detect the scattered electron in the Hall A HRS-L spectrometer (maximum central momentum 4.3 GeV/c) and the emitted photon in a slightly expanded PbF_2 calorimeter. In general, we will not detect the recoil proton. The H(e,e'g)X missing mass resolution is sufficient to isolate the exclusive channel with 3% systematic precision
Deep inelastic scattering of baryons in a modified soft wall model
We calculate the structure functions for unpolarized deep inelastic
scattering of baryons using an AdS/QCD soft wall model that considers a dressed
mass for the bulk fermionic fields. Considering the regime of large Bjorken
parameter x, we compare the results for the proton structure function
with experimental results.Comment: We improved the comparison with experimental data and included more
references, version to appear in EPJ
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