30 research outputs found
Forbidden transitions in neutral and charged current interactions between low-energy neutrinos and Argon
Background: The study of low-energy neutrinos and their interactions with
atomic nuclei is crucial to several open problems in physics, including the
neutrino mass hierarchy, CP-violation, candidates of Beyond Standard Model
physics and supernova dynamics. Examples of experiments include CAPTAIN at SNS
as well as DUNE's planned detection program of supernova neutrinos. Purpose: We
present cross section calculations for quasielastic charged current and neutral
current neutrinos at low energies, with a focus on Ar. We also take a
close look at pion decay-at-rest neutrino spectra, which are used in e.g. the
SNS experiment at Oakridge. Method and results: We employ a Hartree Fock +
Continuum Random Phase Approximations (HF+CRPA) framework, which allows us to
model the responses and include the effects of long-range correlations. It is
expected to provide a good framework to calculate forbidden transitions, whose
contribution which we show to be non-negligible. Conclusions: Forbidden
transitions can be expected to contribute sizeably to the reaction strength at
typical low-energy kinematics, such as DAR neutrinos. Modeling and Monte Carlo
simulations need to take all due care to account for the influence of their
contributions.Comment: 11 pages, 16 figures; minor corrections to v
Nuclear effects in electron- and neutrino-nucleus scattering within a relativistic quantum mechanical framework
We study the impact of the description of the knockout nucleon wave function
on electron- and neutrino-induced quasielastic and single-pion production cross
sections. We work in a fully relativistic and quantum mechanical framework,
where the relativistic mean-field model is used to describe the target nucleus.
The focus is on Pauli blocking and the distortion of the final nucleon, these
two nuclear effects are separated and analyzed in detail. We find that a proper
quantum mechanical treatment of these effects is crucial to provide the correct
magnitude and shape of the inclusive cross section. Also, this seems to be key
to predict the right ratio of muon- to electron-neutrino cross sections at very
forward scattering angles.Comment: 14 pages, 14 figure
Lepton kinematics in low-energy neutrino-argon interactions
Background: Neutrinos in the low-energy regime provide a gateway to a wealth of interesting physics. While plenty of literature exists on detailing the calculation and measurement of total reaction strengths, relatively little attention is paid to the measurement and modeling of the final lepton through differential cross sections at low energies, despite the experimental importance. Purpose: We calculate differential cross sections for low-energy neutrino-nucleus scattering. We examine the role played by forbidden transitions in these distributions and how this differs across different energies and nuclear target masses. Attention is also paid to predictions for typical experimental neutrino spectra. Method: The differential cross sections are calculated within a continuum random-phase approximation framework, which allows us to include collective excitations induced by long-range correlations. The Coulomb interaction of the final lepton in charged current events is treated in an effective way. Results: Kinematic distributions are calculated for O-16, Ar-40, and Pb-208. The Ar-40 model results are compared for charged current (CC) (nu(e), e(-)) reactions to events generated by the Modeling of Argon Reaction Low-energy Yields (MARLEY) event generator [S. Gardiner, Ph.D. thesis, University of California, Davis (2018)], with noticeable discrepancies. Conclusion: Forbidden transitions have a marked effect on the kinematic distributions of the final lepton at low-energy kinematics, such as for decay-at-rest neutrinos or for a Fermi-Dirac spectrum at low temperature. This could introduce biases in experimental analyses. Backward scattering is noticeably more prominent than with MARLEY
Lepton-Nucleus Interactions within Microscopic Approaches
This review paper emphasizes the significance of microscopic calculations
with quantified theoretical error estimates in studying lepton-nucleus
interactions and their implications for electron-scattering and accelerator
neutrino-oscillation measurements. We investigate two approaches: Green's
Function Monte Carlo and the extended factorization scheme, utilizing realistic
nuclear target spectral functions. In our study, we include relativistic
effects in Green's Function Monte Carlo and validate the inclusive
electron-scattering cross section on carbon using available data. We compare
the flux folded cross sections for neutrino-Carbon scattering with T2K and
MINERA experiments, noting the substantial impact of relativistic effects
in reducing the theoretical curve strength when compared to MINERA data.
Additionally, we demonstrate that quantum Monte Carlo-based spectral functions
accurately reproduce the quasi-elastic region in electron-scattering data and
T2K flux folded cross sections. By comparing results from Green's Function
Monte Carlo and the spectral function approach, which share a similar initial
target state description, we quantify errors associated with approximations in
the factorization scheme and the relativistic treatment of kinematics in
Green's Function Monte Carlo.Comment: 30 pages, 9 figure
Modeling quasielastic interactions of monoenergetic kaon decay-at-rest neutrinos
Monoenergetic muon neutrinos at 236 MeV are readily produced in intense
medium-energy proton facilities (2-3~GeV) when a positive kaon decays
at rest (KDAR; ). These neutrinos provide a
unique opportunity to both study the neutrino interaction and probe the nucleus
with a monoenergetic weak-interaction-only tool. We present cross section
calculations for quasielastic scattering of these 236~MeV neutrinos off
C and Ar, paying special attention to low-energy aspects of the
scattering process. Our model takes the description of the nucleus in a
mean-field (MF) approach as the starting point, where we solve Hartree-Fock
(HF) equations using a Skyrme type nucleon-nucleon interaction. Thereby, we
introduce long-range nuclear correlations by means of a continuum random phase
approximation (CRPA) framework where we solve the CRPA equations using a
Green's function method. The model successfully describes () data on
C and Ca in the kinematic region that overlaps with the KDAR
phase space. In addition to these results, we present future
prospects for precision KDAR cross section measurements and applications of our
calculations in current and future experiments that will utilize these
neutrinos
Assessing the theory-data tension in neutrino-induced charged pion production: the effect of final-state nucleon distortion
Pion production on nuclei constitutes a significant part of the total cross
section in experiments involving few-GeV neutrinos. Combined analyses of data
on deuterium and heavier nuclei points to tensions between the bubble chamber
data and the data of the MINERA experiment, which are often ascribed to
unspecified nuclear effects. To understand the origin of these tensions, a
microscopic quantum mechanical framework is needed to compute nuclear matrix
elements. We use the local approximation to the relativistic distorted wave
impulse approximation (RDWIA) to assess the role of final-state nucleon
distortion. To perform this comparison under conditions relevant to neutrino
experiments, we compute cross sections for the MINERA and T2K charged pion
production datasets. The inclusion of nucleon distortion leads to a reduction
of the cross section up to 10\%, but to no significant change in shape of the
flux-averaged cross sections. Results with and without distortion compare
favorably to experimental data, with the exception of the low- MINERA
data. We point out that hydrogen target data from BEBC is also
overpredicted at low-, and that the discrepancy is similar in shape and
magnitude to what is found in comparison to MINERA data. Including nucleon
distortion alone cannot explain the overprediction of low- cross sections
measured by MINERA. The similar overprediction of BEBC data on hydrogen
means that it is impossible to ascribe this discrepancy solely to a nuclear
effect. Axial couplings and their dependence should ideally be derived
from more precise data on hydrogen and deuterium
Electron versus muon neutrino induced cross sections in charged current quasi-elastic processes
Differences between and quasielastic cross sections are
essential in neutrino oscillation analyses and CP violation searches for
experiments such as DUNE and T2HK. The ratio of these is however poorly known
experimentally and for certain kinematic regions theoretical models give
contradictory answers. We use two independent mean-field based models to
investigate this ratio using Ar and C targets. We demonstrate
that a proper treatment of the final nucleon's wave function confirms the
dominance of over induced cross sections at forward lepton
scattering.Comment: Updated Fig. 2, minor changes to text, accepted for publication in
Phys. Rev. Letter
Modeling neutrino-induced charged pion production on water at T2K kinematics
Pion production is a significant component of the signal in accelerator-based
neutrino experiments. Over the last years, the MiniBooNE, T2K and MINERvA
collaborations have reported a substantial amount of data on
(anti)neutrino-induced pion production on the nucleus. However, a comprehensive
and consistent description of the whole data set is still missing. We aim at
improving the current understanding of neutrino-induced pion production on the
nucleus. To this end, the comparison of experimental data with theoretical
predictions, preferably based on microscopic models, is essential to
disentangle the different reaction mechanisms involved in the process. To
describe single-pion production (SPP) we use a hybrid model that combines a
low- and a high-energy approach. The low-energy model (LEM) contains resonances
and background terms. At high invariant masses, a high-energy model based on a
Regge approach is employed. The model is implemented in the nucleus using the
relativistic plane wave impulse approximation (RPWIA). We present a comparison
of the hybrid-RPWIA and LEM with the recent neutrino-induced charged current
production cross section on water reported by T2K. In order to judge
the impact of final-state interactions (FSI) we confront our results with those
of the NuWro Monte Carlo generator. The hybrid-RPWIA model and NuWro compare
favorably to the data, albeit that FSI are not included in the former. These
results complement our previous work [Phys. Rev. D 97, 013004 (2018)] where we
compared the models to the MINERvA and MiniBooNE data. The
hybrid-RPWIA model tends to overpredict both the T2K and MINERvA data in
kinematic regions where the largest suppression due to FSI is expected, and
agrees remarkably well with the data in other kinematic regions. On the
contrary, the MiniBooNE data is underpredicted over the whole kinematic range.Comment: 7 pages, 3 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