20 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
-dependence of quasielastic charged-current neutrino-nucleus cross sections
Background: 12C has been and is still widely used in neutrino-nucleus
scattering and oscillation experiments. More recently, 40Ar has emerged as an
important nuclear target for current and future experiments. Liquid argon time
projection chambers (LArTPCs) possess various advantages in measuring
electroweak neutrino-nucleus cross sections. Concurrent theoretical research is
an evident necessity. Purpose: 40Ar is larger than 12C, and one expects nuclear
effects to play a bigger role in reactions. We present inclusive differential
and total cross section results for charged-current neutrino scattering on 40Ar
and perform a comparison with 12C, 16O and 56Fe targets, to find out about the
A-dependent behavior of model predictions. Method: Our model starts off with a
Hartree-Fock description of the nucleus, with the nucleons interacting through
a mean field generated by an effective Skyrme force. Long-range correlations
are introduced by means of a continuum random phase approximation (CRPA)
approach. Further methods to improve the accuracy of model predictions are also
incorporated in the calculations. Results: We present calculations for 12C,
16O, 40Ar and 56Fe, showcasing differential cross sections over a broad range
of kinematic values in the quasielastic regime. We furthermore show flux-folded
results for 40Ar and we discuss the differences between nuclear responses.
Conclusions: At low incoming energies and forward scattering we identify an
enhancement in the 40Ar cross section compared to 12C, as well as in the high
(low ) region across the entire studied range. The
contribution to the folded cross section of the reaction strength at values of
lower than 50 MeV for forward scattering is sizeable.Comment: 9 pages, 8 figures ; complete revision of calculations with updated
discussion of results, Fig. 4 replaced, updated reference list, minor
typographical correction
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
CRPA calculations for neutrino-nucleus scattering : from very low energies to the quasielastic peak
International audienceWe present continuum random phase approximation calculations (CRPA) for neutrino-induced quasielastic scattering off atomic nuclei. The validity of our formalism is checked by a careful confrontation of its results with semi-inclusive double-differential electron scattering data. We pay special attention to excitations in the giant resonance region. The CRPA is well-suited for the description of interactions in this energy range. We aim at providing a uniform description of one-nucleon knockout processes over the whole energy range from threshold to the quasielastic peak. Our calculations point to the fact that low-energy and giant-resonance excitations provide a non-negligible contribution to the interaction strength, especially at forward lepton-scattering angles
Influence of short-range correlations in neutrino-nucleus scattering
Background: Nuclear short-range correlations (SRCs) are corrections to
mean-field wave functions connected with the short-distance behavior of the
nucleon-nucleon interaction. These SRCs provide corrections to lepton- nucleus
cross sections as computed in the impulse approximation (IA). Purpose: We want
to investigate the influence of SRCs on the one-nucleon (1N) and two-nucleon
(2N) knockout channel for muon-neutrino induced processes on a C target
at energies relevant for contemporary measurements. Method: The model adopted
in this work, corrects the impulse approximation for SRCs by shifting the com-
plexity induced by the SRCs from the wave functions to the operators. Due to
the local character of the SRCs, it is argued that the expansion of these
operators can be truncated at a low order. Results: The model is compared with
electron-scattering data, and two-particle two-hole responses are presented for
neutrino scattering. The contributions from the vector and axial-vector parts
of the nuclear current as well as the central, tensor and spin-isospin part of
the SRCs are studied. Conclusions: Nuclear SRCs affect the 1N knockout channel
and give rise to 2N knockout. The exclusive neutrino-induced 2N knockout cross
section of SRC pairs is shown and the 2N knockout contribution to the QE signal
is calculated. The strength occurs as a broad background which extends into the
dip region.Comment: 16 pages, 10 figures. Version published in Physical Review
Correlations in neutrino-nucleus scattering
We present a detailed study of charged-current quasielastic neutrino-nucleus
scattering and of the influence of correlations on one- and two-nucleon
knockout processes. The quasielastic neutrino-nucleus scattering cross
sections, including the influence of long-range correlations, are evaluated
within a continuum random phase approximation approach. The short-range
correlation formalism is implemented in the impulse approximation by shifting
the complexity induced by the correlations from the wave functions to the
operators. The model is validated by confronting cross-section
predictions with electron scattering data in the kinematic region where the
quasielastic channel is expected to dominate. Further, the
C experiments are studied. Double differential cross
sections relevant for neutrino-oscillation C cross
sections, accounting for long- and short-range correlations in the one-particle
emission channel and short-range correlations in the two-particle two-hole
channel, are presented for kinematics relevant for recent neutrino-nucleus
scattering measurements.Comment: 10 pages, 4 figures. Contribution to the proceedings of the 17th
International Workshop on Neutrino Factories and Future Neutrino Beam
Facilities (NUFACT-2015
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
Neutrino-Induced 1-Ï Production
Neutrino-induced pion production constitutes an important contribution to neutrino-nucleus scattering cross sections at intermediate energies. A deep understanding of this process is mandatory for a correct interpretation of neutrino-oscillation experiments. We aim at contributing to the ongoing effort to understand the various experimental results obtained by different collaborations in a wide range of energies. In particular, in this work we analyze recent MiniBooNE and MINERvA charged-current neutrino 1-pion production data. We use a relativistic theoretical approach which accounts for resonant and non-resonant 1-pion production contributions