3,186 research outputs found
Superscaling in electron- and neutrino-nucleus scattering
The superscaling properties of electron scattering data are used to extract
model-independent predictions for neutrino-nucleus cross sections.Comment: Contibution to NuInt05, 4th international workshop on
neutrino-nucleus interaction in the few GeV region, Sept. 26 - 29 2005,
Okayama, Japa
The pion electromagnetic form-factor in a QCD-inspired model
We present detailed numerical results for the pion space-like electromagnetic
form factor obtained within a recently proposed model of the pion
electromagnetic current in a confining light-front QCD-inspired model. The
model incorporates the vector meson dominance mechanism at the quark level,
where the dressed photon with decay in an interacting quark-antiquark
pair,wich absorbs the initial pion and produces the pion in the final state.Comment: Talk given in Light-Cone 2004, Amsterdam,NL., 16-20 August, 2004. To
appear in "Few-Body Systems". 4 pages, 2 figues eps, use Few-Body Sytems
latex styl
Timelike and spacelike hadron form factors, Fock state components and light-front dynamics
A unified description of spacelike and timelike hadron form factors within a
light-front model was successfully applied to the pion. The model is extended
to the nucleon to study the role of pair production and of
nonvalence components in the nucleon form factors. Preliminary results in the
spacelike range are presented.Comment: 4 pages, espcrc1.sty. proceedings of FB XVIII (August 2006, Brazil),
to be published in Nucl. Phys.
Electromagnetic Hadron Form Factors and Higher Fock Components
Investigation of the spacelike and timelike electromagnetic form factors of
hadrons, within a relativistic microscopical model characterized by a small set
of hypothesis, could shed light on the components of hadron states beyond the
valence one. Our relativistic approach has been successfully applied first to
the pion and then the extension to the nucleon has been undertaken. The pion
case is shortly reviewed as an illustrative example for introducing the main
ingredients of our approach, and preliminary results for the nucleon in the
spacelike range are evaluated.Comment: 8 pages, 6 figs, espcrc1.sty included. Proceedings of Fifth
International Conference on Perspectives In Hadronic Physics, ICTP, May
22-26, 200
Electromagnetic form factors of the nucleon in spacelike and timelike regions
An approach for a unified description of the nucleon electromagnetic form
factors in spacelike and timelike regions is presented. The main ingredients of
our model are: a Mandelstam formula for the matrix elements of the nucleon
electromagnetic current; a 3-dimensional reduction of the problem on the
Light-Front performed within the so-called {\tt Propagator Pole Approximation}
({\bf PPA}), which consists in disregarding the analytical structure of the
Bethe-Salpeter amplitudes and of the quark-photon vertex function in the
integration over the minus components of the quark momenta; a dressed
photon vertex in the channel, where the photon is described by its
spin-1, hadronic component.Comment: 8 pages, 9 figs., macro added. Proceedings of the XI Conf. on
Problems in Theoretical Nuclear Physics, Cortona, Oct. 11-14, 200
Emission of neutron-proton and proton-proton pairs in electron scattering induced by meson-exchange currents
We use a relativistic model of meson-exchange currents to compute the
proton-neutron and proton-proton yields in scattering from C in
the 2p-2h channel. We compute the response functions and cross section with the
relativistic Fermi gas model for a range of kinematics from intermediate to
high momentum transfers. We find a large contribution of neutron-proton
configurations in the initial state, as compared to proton-proton pairs. The
different emission probabilities of distinct species of nucleon pairs are
produced in our model only by meson-exchange currents, mainly by the
isobar current. We also analyze the effect of the exchange contribution and
show that the direct/exchange interference strongly affects the determination
of the np/pp ratio.Comment: 5 pages, 6 figure
Nuclear dependence of the 2p2h electroweak response in the Relativistic Fermi Gas model
We present the results of a recent study of meson-exchange two-body currents
in lepton-nucleus inclusive scattering at various kinematics and for different
nuclei within the Relativistic Fermi Gas model. We show that the associated
nuclear response functions at their peaks scale as , for Fermi
momentum going from 200 to 300 MeV/c and momentum transfer from
to 2 GeV/c. This behavior is different from what is found for the
quasielastic response, which scales as . This result can be valuable in
the analyses of long-baseline neutrino oscillation experiments, which need to
implement these nuclear effects in Monte Carlo simulations for different
kinematics and nuclear targets.Comment: 11 pages, 6 figures, Proccedings of the Workshop "Advanced Aspects in
Nuclear Structure and Reactions at Different Energy Scales", 25-28 April
2017, Arbanasi, Bulgari
Density dependence of 2p-2h meson-exchange currents
We analyze the density dependence of the contribution of meson-exchange
currents to the lepton-nucleus inclusive cross section in the two-particle
two-hole channel. The model is based on the Relativistic Fermi Gas, where each
nucleus is characterized by its Fermi momentum . We find that the 2p-2h
nuclear response functions at their peaks scale as for Fermi momentum
going from 200 to 300 MeV/c and momentum transfer from to 2 GeV/c.
This behavior is different from what is found for the quasielastic response,
which scales as . Additionally, the deep scaling region is also
discussed and there the usual scaling behavior is found to be preferable.Comment: 9 pages, 8 figure
Emission of neutron-proton and proton-proton pairs in neutrino scattering
We use a recently developed model of relativistic meson-exchange currents to
compute the neutron-proton and proton-proton yields in
scattering from C in the 2p-2h channel. We compute the response
functions and cross sections with the relativistic Fermi gas model for
different kinematics from intermediate to high momentum transfers. We find a
large contribution of neutron-proton configurations in the initial state, as
compared to proton-proton pairs. In the case of charge-changing neutrino
scattering the 2p-2h cross section of proton-proton emission ({\it i.e.,} np in
the initial state) is much larger than for neutron-proton emission ({\it i.e.,}
two neutrons in the initial state) by a -dependent factor. The
different emission probabilities of distinct species of nucleon pairs are
produced in our model only by meson-exchange currents, mainly by the
isobar current. We also analyze other effects including exchange contributions
and the effect of the axial and vector currents.Comment: 9 pages and 8 figure
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