arXiv subjects

P. R. Casale

Publications and source records attributed to P. R. Casale.

7 recordsLinked to original sources

arXiv2025

Meson-Exchange Currents in Quasielastic Charged-Current Neutrino Reactions with Single-Nucleon Knockout

The effect of meson-exchange currents on charged-current quasielastic neutrino scattering with single-nucleon emission is computed and analyzed within the relativistic Fermi gas model. This contribution arises primarily from the interference between one-body and two-body currents, where the two-body operator excites a 1p1h state in the presence of a second, spectator nucleon. The results obtained show a reduction of the vector, axial and vector-axial transverse response functions and, consequently, a decrease in the total neutrino cross section. In addition to a comparison with the non-relativistic limit, other models are also explored, such as the relativistic mean field model for nuclear matter and the superscaling analysis with relativistic effective mass, both of which yield qualitatively similar results.

hep-ph↗

arXiv2025

Short-Range Correlations and Transverse Response Enhancement from Meson-Exchange Currents

We investigate the role of short-range correlations (SRC) in the transverse nuclear response within the quasielastic peak region, focusing on the 1p1h channel. The calculation is performed in nuclear matter by solving the Bethe-Goldstone equation with the realistic Granada 2013 nucleon-nucleon potential, including both one-body and two-body meson-exchange currents (MEC) of seagull, pion-in-flight, and $Δ$ types. We find that MEC produce a sizable enhancement of the transverse response in the 1p1h channel when acting on correlated nucleon pairs with high-momentum components generated by SRC. This contrasts with the uncorrelated case, where MEC, dominated by the $Δ$ current, can even yield a negative effect. The results are consistent with previous findings based on the correlated basis function approach, supporting the interpretation that SRC play a central role in the transverse response enhancement from MEC.

nucl-th↗

arXiv2025

Improved superscaling description of electron and charged-current neutrino quasielastic scattering using effective mass dynamics

We present an improved version of the Superscaling Analysis with Relativistic Effective Mass, denoted as SuSAM-v2. In the original SuSAM model, a universal scaling function was fitted to a selected set of quasielastic electron scattering (e,e') cross section data, using a phenomenological ansatz inspired by the Relativistic Mean Field model of nuclear matter. In this work, we refine the procedure by first fitting a longitudinal scaling function directly to experimental longitudinal response data. Subsequently, a separate transverse scaling function is extracted from purely transverse data, after subtracting the longitudinal contribution already determined. We find that the resulting transverse scaling function must exhibit an explicit dependence on the momentum transfer q in order to reproduce all kinematics consistently. The resulting SuSAM-v2 model simultaneously describes inclusive quasielastic cross sections and both longitudinal and transverse response functions in electron scattering. The model is then applied to neutrino-nucleus scattering, showing an improved prediction compared to the previous SuSAM-v1 version, due to a more accurate treatment of the relative contributions of the longitudinal and transverse weak nuclear responses.

hep-ph↗

arXiv2025

Interference between Meson Exchange and One-Body Currents in Quasielastic Electron Scattering

In this work, we present a detailed analysis of the interference between meson exchange currents (MEC) and one-body currents in quasielastic electron scattering, with a focus on the sign of this interference in the transverse response for one-particle emission. We prove that the interference of both the Delta and pion-in-flight currents with the one-body current is negative, leading to a partial cancellation with the seagull current. This is mathematically demonstrated within the framework of the Fermi gas model. By comparing these interferences across various independent particle models, both relativistic and non-relativistic, our results indicate that all studied models display the same behavior. This consistency suggests that the interference is negative in models that do not incorporate tensor correlations in the nuclear wave function.

nucl-th↗

arXiv2023

Center-of-mass momentum dependence of short-range correlations with the coarse-grained Granada potential

The effect of the center of mass motion on the high-momentum distributions of correlated nucleon pairs is studied by solving the Bethe-Goldstone equation in nuclear matter with the Granada nucleon-nucleon potential. We show that this coarse-grained potential reduces the problem to an algebraic linear system of five (ten) equations for uncoupled (coupled) partial waves that can be easily solved. The corresponding relative wave functions of correlated pn, pp and nn pairs are computed for different values of their CM momentum. We find that the pn pairs dominate the high-momentum tail of the relative momentum distribution, and that this only depends marginally on center of mass momentum. Our results provide further justification and agreement for the factorization approximation commonly used in the literature. This approximation assumes that the momentum distribution of nucleon pairs can be factorized as the product of the center of mass momentum distribution and the relative momentum distribution.

nucl-th↗

arXiv2023

Extended superscaling with two-particle emission in electron and neutrino scattering

An extended superscaling analysis of quasielastic electron scattering data is proposed by parametrizing the scaling function as the sum of a symmetric function corresponding to the emission of a single particle plus a contribution from the phase space of two-particle emission. The phase space of two-particle emission (2p2h) is multiplied by a q-dependent parameter that has been fitted to describe the tail behavior of the scaling function. This approach allows for an alternative description of the quasielastic electron scattering data, incorporating the contributions from both single-particle and two-particle emission processes induced by the one-body current and explaining the asymmetry of the scaling function. In a factorized schematic model based on the independent-pair approximation, the 2p2h parameter is related to the high-momentum distribution of the pair averaged over 2p-2h excitations. However, in the phenomenological fitting approach undertaken here, this coefficient includes other contributions such as interference with two-body currents and effects of the final-state interactions. We present predictions for the inclusive two-nucleon emission cross section induced by electrons and neutrinos.

nucl-th↗

arXiv2023

Improved Superscaling in Quasielastic Electron Scattering with Relativistic Effective Mass

Superscaling in electron scattering from nuclei is re-examined paying special attention to the definition of the averaged single-nucleon responses. The validity of the extrapolation of nucleon responses in the Fermi gas has been examined, which previously lacked a theoretical foundation. To address this issue, we introduce new averaged responses with a momentum distribution smeared around the Fermi surface, allowing for momenta above the Fermi momentum. This approach solves the problem of negativity in the extrapolation away from the scaling region and, at the same time, validates its use in the scaling analysis. This work has important implications for the interpretation of scaling data and contributes to the development of a more complete understanding of the scaling approach.

nucl-th↗