352 research outputs found
D=2 gluon condensate and QCD propagators at finite temperature
We calculate the dimension two gluon condensate contribution to quark, gluon
and ghost propagators at finite temperature.Comment: Minor modifications. Accepted in PL
Neutrino and antineutrino CCQE scattering in the SuperScaling Approximation from MiniBooNE to NOMAD energies
We compare the predictions of the SuperScaling model for charged current
quasielastic muonic neutrino and antineutrino scattering from C with
experimental data spanning an energy range up to 100 GeV. We discuss the
sensitivity of the results to different parametrizations of the nucleon vector
and axial-vector form factors. Finally, we show the differences between
electron and muon (anti-)neutrino cross sections relevant for the STORM
facility.Comment: 14 pages, 7 figures; v2: small corrections in the text and two added
references; version accepted for publication by Phys. Lett.
Extensions of Superscaling from Relativistic Mean Field Theory: the SuSAv2 Model
We present a systematic analysis of the quasielastic scaling functions
computed within the Relativistic Mean Field (RMF) Theory and we propose an
extension of the SuperScaling Approach (SuSA) model based on these results. The
main aim of this work is to develop a realistic and accurate phenomenological
model (SuSAv2), which incorporates the different RMF effects in the
longitudinal and transverse nuclear responses, as well as in the isovector and
isoscalar channels. This provides a complete set of reference scaling functions
to describe in a consistent way both processes and the
neutrino/antineutrino-nucleus reactions in the quasielastic region. A
comparison of the model predictions with electron and neutrino scattering data
is presented.Comment: 19 pages, 24 figure
The frozen nucleon approximation in two-particle two-hole response functions
We present a fast and efficient method to compute the inclusive two-particle
two-hole (2p-2h) electroweak responses in the neutrino and electron
quasielastic inclusive cross sections. The method is based on two
approximations. The first neglects the motion of the two initial nucleons below
the Fermi momentum, which are considered to be at rest. This approximation,
which is reasonable for high values of the momentum transfer, turns out also to
be quite good for moderate values of the momentum transfer . The
second approximation involves using in the "frozen" meson-exchange currents
(MEC) an effective -propagator averaged over the Fermi sea. Within the
resulting "frozen nucleon approximation", the inclusive 2p-2h responses are
accurately calculated with only a one-dimensional integral over the emission
angle of one of the final nucleons, thus drastically simplifying the
calculation and reducing the computational time. The latter makes this method
especially well-suited for implementation in Monte Carlo neutrino event
generators.Comment: 8 pages, 5 figures and 1 tabl
Two-nucleon emission in neutrino and electron scattering from nuclei: the modified convolution approximation
The theoretical formalism of inclusive lepton-nucleus scattering in the
two-nucleon emission channel is discussed in the context of a simplified
approach, the modified convolution approximation. This allows one to write the
2p2h responses of the relativistic Fermi gas as a folding integral of two 1p1h
responses with the energies and momenta transferred to each nucleon. The idea
behind this method is to introduce different average momenta for the two
initial nucleons in the matrix elements of the two-body current, with the
innovation that they depend on the transferred energies and momenta. This
method treats exactly the two-body phase space kinematics, and reduces the
formulae of the response functions from seven-dimensional integrals over
momenta to much simpler three-dimensional ones. The applicability of the method
is checked by comparing with the full results within a model of electroweak
meson-exchange currents. The predictions are accurate enough, especially in the
low-energy threshold region where the average momentum approximation works the
best.Comment: 35 pages, 13 figure
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
Charged-current inclusive neutrino cross sections in the SuperScaling model including quasielastic, pion production and meson-exchange contributions
Charged current inclusive neutrino-nucleus cross sections are evaluated using
the superscaling model for quasielastic scattering and its extension to the
pion production region. The contribution of two-particle-two-hole vector
meson-exchange current excitations is also considered within a fully
relativistic model tested against electron scattering data. The results are
compared with the inclusive neutrino-nucleus data from the T2K and SciBooNE
experiments. For experiments where GeV, the
three mechanisms considered in this work provide good agreement with the data.
However, when the neutrino energy is larger, effects from beyond the
also appear to be playing a role. The results show that processes induced by
two-body currents play a minor role at the kinematics considered.Comment: 10 pages, 7 figure
Nuclear effects in neutrino and antineutrino CCQE scattering at MINERvA kinematics
We compare the charged-current quasielastic neutrino and antineutrino
observables obtained in two different nuclear models, the phenomenological
SuperScaling Approximation and the Relativistic Mean Field approach, with the
recent data published by the MINERvA Collaboration. Both models provide a good
description of the data without the need of an ad hoc increase in the mass
parameter in the axial-vector dipole form factor. Comparisons are also made
with the MiniBooNE results where different conclusions are reached.Comment: 6 pages, 7 figures, Accepted for publication in Physical Review
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