59 research outputs found
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
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
Low-energy neutrino-nucleus interactions and beta-beam neutrino
We present an overview of neutrino-nucleus scattering at low energies with cross sections obtained within a continuum random phase approximation (CRPA) formalism. We highlight potential applications of beta-beam neutrino experiments for neutrino astrophysics. Our calculations are compared with MiniBooNe data at intermediate energies
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
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
-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
Quark--hadron duality in lepton scattering off nuclei
A phenomenological study of quark--hadron duality in electron and neutrino
scattering on nuclei is performed. We compute the structure functions and
in the resonance region within a framework that includes the
Dortmund-group model for the production of the {f}{i}rst four lowest-lying
baryonic resonances and a relativistic mean-field model for nuclei. We consider
four-momentum transfers between 0.2 and 2.5 GeV. The results indicate that
nuclear effects play a different role in the resonance and DIS region. We find
that global but not local duality works well. In the studied range of
four-momentum transfers, the integrated strength of the computed nuclear
structure functions in the resonance region, is considerably lower than the DIS
one.Comment: 18 pages, 11 figure
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