116 research outputs found
The generalised relativistic Lindhard functions
We present here analytic expressions for the generalised Lindhard function,
also referred to as Fermi Gas polarisation propagator, in a relativistic
kinematic framework and in the presence of various resonances and vertices.
Particular attention is payed to its real part, since it gives rise to
substantial difficulties in the definition of the currents entering the
dynamics.Comment: 48 pages, 2 figures, to be published in EPJ
Inelastic electron-nucleus scattering and scaling at high inelasticity
Highly inelastic electron scattering is analyzed within the context of the
unified relativistic approach previously considered in the case of quasielastic
kinematics. Inelastic relativistic Fermi gas modeling that includes the
complete inelastic spectrum - resonant, non-resonant and Deep Inelastic
Scattering - is elaborated and compared with experimental data. A
phenomenological extension of the model based on direct fits to data is also
introduced. Within both models, cross sections and response functions are
evaluated and binding energy effects are analyzed. Finally, an investigation of
the second-kind scaling behavior is also presented.Comment: 39 pages, 13 figures; formalism extended and slightly reorganized,
conclusions extended; to appear in Phys. Rev.
\pi N scattering in relativistic baryon chiral perturbation theory revisited
We have analyzed pion-nucleon scattering using the manifestly relativistic
covariant framework of Infrared Regularization up to {\cal O}(q^3) in the
chiral expansion, where q is a generic small momentum. We describe the
low-energy phase shifts with a similar quality as previously achieved with
Heavy Baryon Chiral Perturbation Theory, \sqrt{s}\lesssim1.14 GeV. New values
are provided for the {\cal O}(q^2) and {\cal O}(q^3) low-energy constants,
which are compared with previous determinations. This is also the case for the
scattering lengths and volumes. Finally, we have unitarized the previous
amplitudes and as a result the energy range where data are reproduced increases
significantly.Comment: 26 pages, 5 figures, 5 table
Nuclear effects in electron reactions and their impact on neutrino processes
We suggest that superscaling in electroweak interactions with nuclei, namely
the observation that the reduced electron-nucleus cross sections are to a large
degree independent of the momentum transfer and of the nuclear species, can be
used as a tool to obtain precise predictions for neutrino-nucleus cross
sections in both charged and neutral current-induced processes.Comment: 11 pages, 7 figures, proceedings of NUINT09, 6th International
Workshop of Neutrino-Nucleus Interactions in the Few-Gev Region, Sitges
(Spain), May 18-22, 200
Neutrino Interactions Importance for Nuclear Physics
We review the general interplay between Nuclear Physics and neutrino-nucleus
cross sections at intermediate and high energies. The effects of different
reaction mechanisms over the neutrino observables are illustrated with examples
in calculations using several nuclear models and ingredients.Comment: To appear in the proceedings of 6th International Workshop on
Neutrino-Nucleus Interactions in the Few-GeV Region (NuInt09), Sitges, Spain,
18 - 22 May 200
Pion induced double charge exchange reactions in the Delta resonance region
We have applied the Giessen BUU (GiBUU) transport model to the description of
the double charge exchange (DCX) reaction of pions with different nuclear
targets at incident kinetic energies of 120-180 MeV . The DCX process is highly
sensitive to details of the interactions of pions with the nuclear medium and,
therefore, represents a major benchmark for any model of pion scattering off
nuclei at low and intermediate energies. The impact of surface effects, such as
the neutron skins of heavy nuclei, is investigated. The dependence of the total
cross section on the nuclear mass number is also discussed. We achieve a good
quantitative agreement with the extensive data set obtained at LAMPF.
Furthermore, we compare the solutions of the transport equations obtained in
the test-particle ansatz using two different schemes - the full and the
parallel ensemble method.Comment: 14 pages,9 figure
The two pion decay of the Roper resonance
We evaluate the two pion decay of the Roper resonance in a model where
explicit re-scattering of the two final pions is accounted for by the use of
unitarized chiral perturbation theory. Our model does not include an explicit
or scalar-isoscalar meson decay mode, instead it
generates it dynamically by means of the pion re-scattering. The two ways,
explicit or dynamically generated, of introducing this decay channel have very
different amplitudes.
Nevertheless, through interference with the other terms of the model we are
able to reproduce the same phenomenology as models with explicit consideration
of the meson.Comment: 17 latex pages, 11 eps figures. A few misprints corrected. A few new
references. Version accepted for publication in Phys. Rev.
Meson exchange currents in pion double charge exchange at high energies
In this letter we study the high-energy behaviour of the forward differential cross section for the O-18(pi(+),pi(-))Ne-18 double charge exchange reaction. We have evaluated the sequential and the meson exchange current mechanisms. The meson exchange current contribution shows a very weak energy dependence and becomes relevant at incident pion kinetic energies above 600 MeV
Electroweak Radiative Corrections to Parity-Violating Electroexcitation of the
We analyze the degree to which parity-violating (PV) electroexcitation of the
resonance may be used to extract the weak neutral axial vector
transition form factors. We find that the axial vector electroweak radiative
corrections are large and theoretically uncertain, thereby modifying the
nominal interpretation of the PV asymmetry in terms of the weak neutral form
factors. We also show that, in contrast to the situation for elastic electron
scattering, the axial PV asymmetry does not vanish at the photon
point as a consequence of a new term entering the radiative corrections. We
argue that an experimental determination of these radiative corrections would
be of interest for hadron structure theory, possibly shedding light on the
violation of Hara's theorem in weak, radiative hyperon decays.Comment: RevTex, 76 page
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