129 research outputs found
Pion production within the hybrid relativistic plane wave impulse approximation model at MiniBooNE and MINERvA kinematics
The hybrid model for electroweak single-pion production (SPP) off the
nucleon, presented in [Gonz\'alez-Jim\'enez et al., Phys. Rev. D 95, 113007
(2017)], is extended here to the case of incoherent pion-production on the
nucleus. Combining a low-energy model with a Regge approach, this model
provides valid predictions in the entire energy region of interest for current
and future accelerator-based neutrino-oscillation experiments. The Relativistic
Mean-Field model is used for the description of the bound nucleons while the
outgoing hadrons are considered as plane waves. This approach, known as
Relativistic Plane-Wave Impulse Approximation (RPWIA), is a first step towards
the development of more sophisticated models, it is also a test of our current
understanding of the elementary reaction. We focus on the charged-current
()-nucleus interaction at MiniBooNE and MINERvA kinematics. The
effect on the cross sections of the final-state interactions, which affect the
outgoing hadrons on their way out of the nucleus, is judged by comparing our
results with those from the NuWro Monte Carlo event generator. We find that the
hybrid-RPWIA predictions largely underestimate the MiniBooNE data. In the case
of MINERvA, our results fall below the -induced 1 production data,
while a better agreement is found for -induced 1 and
-induced 1 production.Comment: 13 pages, 10 figure
Seagull and pion-in-flight currents in neutrino-induced and knockout
[Background] The neutrino-nucleus () cross section is a major source
of systematic uncertainty in neutrino-oscillation studies. A precise
scattering model, in which multinucleon effects are incorporated, is pivotal
for an accurate interpretation of the data. [Purpose] In interactions,
meson-exchange currents (MECs) can induce two-nucleon () knockout from the
target nucleus, resulting in a two-particle two-hole (2p2h) final state. They
also affect single nucleon () knockout reactions, yielding a one-particle
one-hole (1p1h) final state. Both channels affect the inclusive strength. We
present a study of axial and vector, seagull and pion-in-flight currents in
muon-neutrino induced and knockout reactions on C. [Method]
Bound and emitted nucleons are described as Hartree-Fock wave functions. For
the vector MECs, the standard expressions are used. For the axial current,
three parameterizations are considered. The framework developed here allows for
a treatment of MECs and short-range correlations (SRCs). [Results] Results are
compared with electron-scattering data and with literature. The strengths of
the seagull, pion-in-flight and axial currents are studied separately and
double differential cross sections including MECs are compared with results
including SRCs. A comparison with MiniBooNE and T2K data is presented.
[Conclusions] In the 1p1h channel, the effects of the MECs tend to cancel each
other, resulting in a small effect on the double differential cross section.
knockout processes provide a small contribution to the inclusive double
differential cross section, ranging from the knockout threshold into the
dip region. A fair agreement with the MiniBooNE and T2K data is reached.Comment: 16 pages, 10 figure
Impact of low-energy nuclear excitations on neutrino-nucleus scattering at MiniBooNE and T2K kinematics
[Background] Meticulous modeling of neutrino-nucleus interactions is
essential to achieve the unprecedented precision goals of present and future
accelerator-based neutrino-oscillation experiments. [Purpose] Confront our
calculations of charged-current quasielastic cross section with the
measurements of MiniBooNE and T2K, and to quantitatively investigate the role
of nuclear-structure effects, in particular, low-energy nuclear excitations in
forward muon scattering. [Method] The model takes the mean-field (MF) approach
as the starting point, and solves Hartree-Fock (HF) equations using a Skyrme
(SkE2) nucleon-nucleon interaction. Long-range nuclear correlations are taken
into account by means of the continuum random-phase approximation (CRPA)
framework. [Results] We present our calculations on flux-folded double
differential, and flux-unfolded total cross sections off C and compare
them with MiniBooNE and (off-axis) T2K measurements. We discuss the importance
of low-energy nuclear excitations for the forward bins. [Conclusions] The CRPA
predictions describe the gross features of the measured cross sections. They
underpredict the data (more in the neutrino than in the antineutrino case)
because of the absence of processes beyond pure quasielastic scattering in our
model. At very forward muon scattering, low-energy nuclear excitations ( 50 MeV) account for nearly 50% of the flux-folded cross section.Comment: 8 pages, 9 figures. Version published in Physical Review
Angular distributions in Monte Carlo event generation of weak single-pion production
One of the substantial sources of systematic errors in neutrino oscillation
experiments that utilize neutrinos from accelerator sources stems from a lack
of precision in modeling single-pion production (SPP). Oscillation analyses
rely on Monte Carlo event generators (MC), providing theoretical predictions of
neutrino interactions on nuclear targets. Pions produced in these processes
provide a significant fraction of oscillation signal and background on both
elementary scattering and detector simulation levels. Thus, it is of critical
importance to develop techniques that will allow us to accommodate
state-of-the-art theoretical models describing SPP into MCs.
In this work, we investigate various algorithms to implement single-pion
production models in Monte Carlo event generators. Based on comparison studies,
we propose a novel implementation strategy that combines satisfactory
efficiency with high precision in reproducing details of theoretical models
predictions, including pion angular distributions. The proposed implementation
is model-independent, thereby providing a framework that can include any model
for SPP. We have tested the new algorithm with the Ghent Low Energy Model for
single-pion production implemented in the NuWro Monte Carlo event generator.Comment: 13 pages, 8 figure
Angular distributions in Monte Carlo event generation of weak single-pion production
One of the substantial sources of systematic errors in neutrino oscillation experiments that utilize neutrinos from accelerator sources stems from a lack of precision in modeling single-pion production (SPP). Oscillation analyses rely on Monte Carlo event generators (MC), providing theoretical predictions of neutrino interactions on nuclear targets. Pions produced in these processes provide a significant fraction of oscillation signal and background on both elementary scattering and detector simulation levels. Thus, it is of critical importance to develop techniques that will allow us to accommodate state-of-the-art theoretical models describing SPP into MCs. In this work, we investigate various algorithms to implement single-pion production models in Monte Carlo event generators. Based on comparison studies, we propose a novel implementation strategy that combines satisfactory efficiency with high precision in reproducing details of theoretical models predictions, including pion angular distributions. The proposed implementation is model-independent, thereby providing a framework that can include any model for SPP. We have tested the new algorithm with the Ghent low energy model for single-pion production implemented in the NuWro Monte Carlo event generator
Effect of Surface Treatments on the Nanomechanical Properties of Human Hair.
The structural properties of hair are largely determined by the state of the surface. Advanced imaging modes of atomic force microscopy, where the surface mechanics can be correlated with surface topography, have been used to spatially map variations in hair surfaces following chemical and mechanical treatments. Through analysis of multilayered data obtained in this way, we show that the processes of bleaching and combing of hair not only alter the surface roughness, but also alter the mechanical stiffness, adhesion properties, and surface potential of hair, in terms of the mean values and their distributions. These treatments are shown to have a significant effect on the nanoscale surface properties, consistent with what has previously been observed at the macroscopic fiber-level scale.Unileve
Towards a more complete description of nucleon distortion in lepton-induced single-pion production at low-
Theoretical predictions for lepton-induced single-pion production (SPP) on
C are revisited in order to assess the effect of different treatments of
the current operator. On one hand we have the asymptotic approximation, which
consists in replacing the particle four-vectors that enter in the operator by
their asymptotic values, i.e., their values out of the nucleus. On the other
hand we have the full calculation, which is a more accurate approach to the
problem. We also compare with results in which the final nucleon is described
by a relativistic plane wave, to rate the effect of the nucleon distortion. The
study is performed for several lepton kinematics, reproducing inclusive and
semi-inclusive cross sections belonging to the low- region (between 0.05
and 1 GeV), which is of special interest in charged-current (CC)
neutrino-nucleus 1 production. Inclusive electron results are compared
with experimental data. We find non-trivial corrections comparable in size with
the effect of the nucleon distortion, namely, corrections up to 6\%, either
increasing or diminishing the asymptotic prediction, and a shift of the
distributions towards higher energy transfer. For the semi-inclusive cross
sections, we observe the correction to be prominent mainly at low values of the
outgoing nucleon kinetic energy. Finally, for CC neutrino-induced 1
production, we find a reduction at low- with respect to both the
plane-wave approach and the asymptotic case
Neutrino-induced pion production from nuclei at medium energies
We present a fully relativistic formalism for describing neutrino-induced
-mediated single-pion production from nuclei. We assess the ambiguities
stemming from the interactions. Variations in the cross sections of
over 10% are observed, depending on whether or not magnetic-dipole dominance is
assumed to extract the vector form factors. These uncertainties have a direct
impact on the accuracy with which the axial-vector form factors can be
extracted. Different predictions for induce up to 40-50% effects
on the -production cross sections. To describe the nucleus, we turn to
a relativistic plane-wave impulse approximation (RPWIA) using realistic
bound-state wave functions derived in the Hartree approximation to the
- Walecka model. For neutrino energies larger than 1 GeV, we
show that a relativistic Fermi-gas model with appropriate binding-energy
correction produces comparable results as the RPWIA which naturally includes
Fermi motion, nuclear-binding effects and the Pauli exclusion principle.
Including medium modifications yields a 20 to 25% reduction of the
RPWIA cross section. The model presented in this work can be naturally extended
to include the effect of final-state interactions in a relativistic and
quantum-mechanical way. Guided by recent neutrino-oscillation experiments, such
as MiniBooNE and K2K, and future efforts like MINERA, we present ,
, and various semi-inclusive distributions, both for a free nucleon and
carbon, oxygen and iron targets.Comment: 25 pages, 14 figure
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