743 research outputs found
Understanding Supernova Neutrino Physics using Low-Energy Beta-Beams
We show that fitting linear combinations of low-energy beta-beam spectra to
supernova-neutrino energy-distributions reconstructs the response of a nuclear
target to a supernova flux in a very accurate way. This allows one to make
direct predictions about the supernova-neutrino signal in a terrestrial
neutrino detector.Comment: To appear in the proceedings of International School of Nuclear
Physics: 27th Course: "Neutrinos in Cosmology, in Astro, Particle and Nuclear
Physics". Erice, Sicily, Italy, 16-2
Reconstructing supernova-neutrino spectra using low-energy beta-beams
Only weakly interacting, neutrinos are the principal messengers reaching us
from the center of a supernova. Terrestrial neutrino telescopes, such as SNO
and SuperKamiokande, can provide precious information about the processes in
the core of a collapsing and exploding star. But the information about the
supernova that a neutrino detector can supply, is restricted by the fact that
little experimental data on the neutrino-nucleus cross sections exists and by
the uncertainties in theoretical calculations. In this letter, we propose a
novel procedure that determines the response of a target nucleus in a
supernova-neutrino detector directly, by using low-energy beta-beams. We show
that fitting 'synthetic' spectra, constructed by taking linear combinations of
beta-beam spectra, to the original supernova-neutrino spectra reproduces the
folded differential cross sections very accurately. Comparing the response in a
terrestrial detector to these synthetic responses provides a direct way to
determine the main parameters of the supernova-neutrino energy-distribution.Comment: 4 page
A doubly-periodic structure for the study of inhomogeneous bulk fermion matter with spatial localizations
We present a method that offers perspectives to perform fully antisymmetrized
simulations for inhomogeneous bulk fermion matter. The technique bears
resemblance to classical periodic boundary conditions, using localized
single-particle states. Such localized states are an ideal tool to discuss
phenomena where spatial localization plays an important role. The
antisymmetrisation is obtained introducing a doubly-periodic structure in the
many-body fermion wave functions. This results in circulant matrices for the
evaluation of expectation values, leading to a computationally tractable
formalism to study fully antisymmetrized bulk fermion matter. We show that the
proposed technique is able to reproduce essential fermion features in an
elegant and computationally advantageous manner
Thermodynamical properties of a mean-field plus pairing model and applications for the Fe nuclei
A mean-field plus pairing model for atomic nuclei in the Fe region was
studied using a finite-temperature quantum Monte-Carlo method. We present
results for thermodynamical quantities such as the internal energy and the
specific heat. These results give indications of a phase transition related to
the pairing amongst nucleons, around temperatures of 0.7 MeV. The influence of
the residual interaction and of the size of the model space on the nuclear
level densities is discussed too.Comment: 23 pages, including 17 eps figure
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
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
Extracting the Weinberg angle at intermediate energies
A recent experiment by the NuTeV collaboration resulted in a surprisingly
high value for the weak mixing angle . The Paschos-Wolfenstein
relation, relating neutrino cross sections to the Weinberg angle, is of pivotal
importance in the NuTeV analysis. In this work, we investigate the sensitivity
of the Paschos-Wolfenstein relation to nuclear structure aspects at neutrino
energies in the few GeV range. Neutrino-nucleus cross sections are calculated
for O and Fe target nuclei within a relativistic quasi-elastic
nucleon-knockout model.Comment: To appear in the proceedings of International School of Nuclear
Physics: 27th Course: "Neutrinos in Cosmology, in Astro, Particle and Nuclear
Physics", Erice, Sicily, Italy, 16-24 Sep 200
Untangling supernova-neutrino oscillations with beta-beam data
Recently, we suggested that low-energy beta-beam neutrinos can be very useful
for the study of supernova neutrino interactions. In this paper, we examine the
use of a such experiment for the analysis of a supernova neutrino signal. Since
supernova neutrinos are oscillating, it is very likely that the terrestrial
spectrum of supernova neutrinos of a given flavor will not be the same as the
energy distribution with which these neutrinos were first emitted. We
demonstrate the efficacy of the proposed method for untangling multiple
neutrino spectra. This is an essential feature of any model aiming at gaining
information about the supernova mechanism, probing proto-neutron star physics,
and understanding supernova nucleosynthesis, such as the neutrino process and
the r-process. We also consider the efficacy of different experimental
approaches including measurements at multiple beam energies and detector
configurations.Comment: 13 pages, 11 figures, accepted for publication in Phys. Rev.
Identifying neutrinos and antineutrinos in neutral-current scattering reactions
We study neutrino-induced nucleon knockout from nuclei. Expressions for the
induced polarization are derived within the framework of the
independent-nucleon model and the non-relativistic plane-wave approximation.
Large dissimilarities in the nucleon polarization asymmetries are observed
between neutrino- and antineutrino-induced processes. These asymmetries
represent a potential way to distinguish between neutrinos and antineutrinos in
neutral-current neutrino-scattering on nuclei. We discuss astrophysical
applications of these polarization asymmetries. Our findings are illustrated
for neutrino scattering on O and Pb.Comment: 5 pages, 5 figures, accepted for publication in Phys. Rev. Let
Physics of a partially ionized gas relevant to galaxy formation simulations -- the ionization potential energy reservoir
Simulation codes for galaxy formation and evolution take on board as many
physical processes as possible beyond the standard gravitational and
hydrodynamical physics. Most of this extra physics takes place below the
resolution level of the simulations and is added in a sub-grid fashion.
However, these sub-grid processes affect the macroscopic hydrodynamical
properties of the gas and thus couple to the on-grid physics that is explicitly
integrated during the simulation. In this paper, we focus on the link between
partial ionization and the hydrodynamical equations. We show that the energy
stored in ions and free electrons constitutes a potential energy term which
breaks the linear dependence of the internal energy on temperature. Correctly
taking into account ionization hence requires modifying both the equation of
state and the energy-temperature relation. We implemented these changes in the
cosmological simulation code Gadget2. As an example of the effects of these
changes, we study the propagation of Sedov-Taylor shock waves through an
ionizing medium. This serves as a proxy for the absorption of supernova
feedback energy by the interstellar medium. Depending on the density and
temperature of the surrounding gas, we find that up to 50% of the feedback
energy is spent ionizing the gas rather than heating it. Thus, it can be
expected that properly taking into account ionization effects in galaxy
evolution simulations will drastically reduce the effects of thermal feedback.
To the best of our knowledge, this potential energy term is not used in current
simulations of galaxy formation and evolution.Comment: 8 pages, 4 figures. Accepted for publication in Ap
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