66 research outputs found
The Neutron Spin Structure Function from the Deuteron Data in the Resonance Region
Nuclear effects in the spin-dependent structure function of the
deuteron are studied in the kinematics of future experiments at CEBAF, (). The magnitude of nuclear effects is found to
be significantly larger than the one occurring in deep inelastic scattering
(). A possibility to measure the neutron
structure functions in the CEBAF experiments with deuterium is analysed. It is
found that disregarding or improperly treating nuclear effects in the region of
nucleon resonances would lead to the ``extraction" of an unreliable function. A
procedure aimed at correctly extracting the neutron structure function from the
deuterium data is illustrated and conclusions about the experimental study of
the dependence of the Gerasimov-Drell-Hearn Sum Rule for the neutron are
drawn.Comment: 11 pages, 4 Postscript figure
Hadronization and final state interaction effects in semi-exclusive Deep Inelastic Scattering off nuclei
Recent calculations of the effects of hadronization and final state
interaction (FSI) in semi-exclusive deep-inelastic scattering (DIS)
processes are reviewed. The basic ingredient underlying these
calculations, {\it viz} the time-dependent effective debris-nucleon cross
section is illustrated, and some relevant results on complex nuclei and the
deuteron are presented. In the latter case, particular attention is paid to the
choice of the kinematics, for such a choice would in principle allow one to
investigate both the structure function of a bound nucleon as well as the
hadronization mechanisms. It is stressed that a planned experiment at Jlab on
the process could be very useful in that respect.Comment: 6 pages, 5 EPS figures. Presented by C. Ciofi degli Atti at the
Fourth International Conference on Hadronic Physics, Trieste (Italy), ICTP
May 12-16, 2003. To appear in EPJ
Relativistic Description of Exclusive Deuteron Breakup Reactions
The exclusive deuteron break-up reaction is analyzed within a covariant
approach based on the Bethe-Salpeter equation with realistic meson-exchange
interaction. Relativistic effects in the cross section, tensor analyzing power
and polarization transfer are investigated in explicit form. Results of
numerical calculations are presented for kinematical conditions in forthcoming
p + D reactions at COSY.Comment: 10 LaTeX pages, 4 eps-figure
The Spin-Dependent Structure Functions of Nuclei in the Meson-Nucleon Theory
A theoretical approach to the investigation of spin-dependent structure
functions in deep inelastic scattering of polarized leptons off polarized
nuclei, based on the effective meson-nucleon theory and operator product
expansion method, is proposed and applied to deuteron and . The explicit
forms of the moments of the deuteron and spin-dependent structure
functions are found and numerical estimates of the influence of nuclear
structure effects are presented.Comment: 42 pages revtex, 7 postscript figures available from above e-mail
upon request. Perugia preprint DFUPG 92/9
Relativistic Contributions to Deuteron Photodisintegration in the Bethe-Salpeter Formalism
In plane wave one-body approximation the reaction of deuteron
photodisintegration is considered in the framework of the Bethe-Salpeter
formalism for two-nucleon system. Results are obtained for deuteron vertex
function, which is the solution of the homogeneous Bethe-Salpeter equation with
a multi-rank separable interaction kernel, with a given analytical form. A
comparison is presented with predictions of non-relativistic, quasipotential
approaches and the equal time approximation. It is shown that important
contributions come from the boost in the arguments of the initial state vertex
function and the boost on the relative energy in the one-particle propagator
due to recoil.Comment: 29 pages, 6 figure
Di-Electron Bremsstrahlung in Intermediate-Energy pn and Dp Collisions
Invariant mass spectra of di-electrons stemming from bremsstrahlung processes
are calculated in a covariant diagrammatical approach for the exclusive
reaction D p \to p_{\rm sp} n p e^+ e^- with detection of a forward spectator
proton, p_{sp}. We employ an effective nucleon-meson theory for parameterizing
the sub-reaction n p \to n p e^+ e^- and, within the Bethe-Salpeter formalism,
derive a factorization of the cross section in the form {d\sigma_{D p \to
p_{\rm sp} n p e^+ e^-}}/{dM}= {d\sigma_{n p \to n p e^+ e^-}}/{dM} \times
kinematical factor related solely to the deuteron (M is the e^+ e^- invariant
mass). The effective nucleon-meson interactions, including the exchange mesons
\pi, \sigma, \omega and \rho as well as excitation and radiative decay of
\Delta(1232), have been adjusted to the process pp \to pp e^+ e^- at energies
below the vector meson production threshold. At higher energies, contributions
from \omega and \rho meson excitations are analyzed in both, NN and Dp
collisions. A relation to two-step models is discussed. Subthreshold
di-electron production in Dp collisions at low spectator momenta is
investigated as well. Calculations have been performed for kinematical
conditions envisaged for forthcoming experiments at HADES
Hadron Propagation in Medium: the Exclusive Process A(e,e'p)B in Few-Nucleon Systems
The mechanism of propagation of hadronic states in the medium is a key point
for understanding particle-nucleus and nucleus-nucleus scattering at high
energies. We have investigated the propagation of a baryon in the exclusive
process A(e,e'p)B in few-nucleon systems using realistic nuclear wave functions
and Glauber multiple scattering theory both in its original form and within a
generalized eikonal approximation. New results for the processes 3He(e,e'p)2H
and 4He(e,e'p)3H are compared with data recently obtained at the Thomas
Jefferson Laboratory (JLAB).Comment: 8 pages, 9 figures, Presented at the Fifth International Conference
on Perspectives in Hadronic Physics -Particle-Nucleus and Nucleus-Nucleus
Scattering at Relativistic Energies-, 22 - 26 May 2006, Trieste, Ital
eta-prime Meson Production in Nucleon-Nucleon Collisions Near The Threshold
The production of mesons in the reactions and at threshold-near energies is analyzed within a covariant effective
meson-nucleon theory. The description of cross section and angular
distributions of the available data in this kinematical region in the
channel is accomplished by including meson currents and nucleon currents with
the resonances , and . Predictions
for the channel are given. The di-electron production from subsequent
Dalitz decay is also
calculated and numerical results are presented for intermediate energy and
kinematics of possible experiments with HADES, CLAS and KEK-PS
A versatile method for simulating pp -> ppe+e- and dp -> pne+e-p_spec reactions
We have developed a versatile software package for the simulation of
di-electron production in and collisions at SIS energies. Particular
attention has been paid to incorporate different descriptions of the Dalitz
decay via a common interface. In addition, suitable
parameterizations for the virtual bremsstrahlung process
based on one-boson exchange models have been implemented. Such simulation tools
with high flexibility of the framework are important for the interpretation of
the di-electron data taken with the HADES spectrometer and the design of
forthcoming experiments
Polarized deep-inelastic scattering from nuclei: a relativistic approach.
We discuss spin-dependent, deep-inelastic scattering from nuclei within a covariant framework. In the relativistic impulse approximation this is described in terms of the amplitude for forward, virtual-photon scattering from an off-mass-shell nucleon. The general structure of the off-shell nucleon hadronic tensor is derived, and the leading behavior of the off-shell nucleon structure functions computed in the Bjorken limit. The formalism, which is valid for nucleons bound inside nuclei with spin 1/2 or 1, is applied to the case of the deuteron.Piller, G. ; Melnitchouk, W. ; Thomas, A.W
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