arXiv subjects

I. Ruiz Simo

Publications and source records attributed to I. Ruiz Simo.

At least 19 recordsLinked to original sources

arXiv2024

Neutrino-nucleon elastic scattering in presence of non-standard interactions: cross sections and nucleon polarizations

New physics beyond the Standard Model (SM) may appear in the form of non-standard neutrino interactions (NSI). We have studied neutral current (anti)neutrino-nucleon scattering in presence of NSI. We obtain that in this scenario, nucleon matrix elements depend not only on the isovector axial nucleon form factor but also on the isoscalar one. For the axial form factors we consequently rely on the quark flavor decomposition performed by QCD simulations in the lattice (LQCD). We have examined cross sections and polarization observables. For the current bounds on diagonal muon flavor NSI couplings we find substantial deviations from the SM predictions in cross sections and transverse polarizations of the outgoing nucleons. In view of the progress in the precision of LQCD determinations of nucleon properties, modern measurements of neutral current (anti)neutrino-nucleon scattering will be in the position to discover or significantly constrain NSI.

hep-ph↗

arXiv2024

Cabibbo suppressed hyperon production off nuclei induced by antineutrinos

In this work we study the production of $Σ$ and $Λ$ hyperons in strangeness changing $ΔS = -1$ charged current interactions of muon antineutrinos on nuclear targets. At the nucleon level, besides quasielastic scattering we consider the inelastic mechanism in which a pion is produced alongside the hyperon. Its relevance for antineutrinos with energies below 2 GeV is conveyed in integrated and differential cross sections. We observe that the distributions on the angle between the hyperon and the final lepton are clearly different for quasielastic and inelastic processes. Hyperon final state interactions, modeled with an intranuclear cascade, lead to a significant transfer from primary produced $Σ$'s into final $Λ$'s. They also cause considerable energy loss, which is apparent in hyperon energy distributions. We have investigated $Λ$ production off ${}^{40}$Ar in the conditions of the recently reported MicroBooNE measurement. We find that the $Λπ$ contribution, dominated by $Σ^*(1385)$ excitation, accounts for about one third of the cross section.

hep-ph↗

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.

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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

Electron Scattering and Neutrino Physics

A thorough understanding of neutrino-nucleus scattering physics is crucial for the successful execution of the entire US neutrino physics program. Neutrino-nucleus interaction constitutes one of the biggest systematic uncertainties in neutrino experiments - both at intermediate energies affecting long-baseline Deep Underground Neutrino Experiment (DUNE), as well as at low energies affecting coherent scattering neutrino program - and could well be the difference between achieving or missing discovery level precision. To this end, electron-nucleus scattering experiments provide vital information to test, assess and validate different nuclear models and event generators intended to be used in neutrino experiments. In this white paper, we highlight connections between electron- and neutrino-nucleus scattering physics at energies ranging from 10s of MeV to a few GeV, review the status of ongoing and planned electron scattering experiments, identify gaps, and layout a path forward that benefits the neutrino community. We also highlight the systemic challenges with respect to the divide between the nuclear and high-energy physics communities and funding that presents additional hurdle in mobilizing these connections to the benefit of neutrino programs.

hep-ex↗

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.

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arXiv2022

Theoretical tools for neutrino scattering: interplay between lattice QCD, EFTs, nuclear physics, phenomenology, and neutrino event generators

Maximizing the discovery potential of increasingly precise neutrino experiments will require an improved theoretical understanding of neutrino-nucleus cross sections over a wide range of energies. Low-energy interactions are needed to reconstruct the energies of astrophysical neutrinos from supernovae bursts and search for new physics using increasingly precise measurement of coherent elastic neutrino scattering. Higher-energy interactions involve a variety of reaction mechanisms including quasi-elastic scattering, resonance production, and deep inelastic scattering that must all be included to reliably predict cross sections for energies relevant to DUNE and other accelerator neutrino experiments. This white paper discusses the theoretical status, challenges, required resources, and path forward for achieving precise predictions of neutrino-nucleus scattering and emphasizes the need for a coordinated theoretical effort involved lattice QCD, nuclear effective theories, phenomenological models of the transition region, and event generators.

hep-ph↗

arXiv2021

Analysis of the kinematic boundaries of the quasi-elastic neutrino-nucleus cross section in the superscaling model with a relativistic effective mass

In this work we obtain the analytical expressions for the boundaries of the charged current quasi-elastic double differential cross section in terms of dimensionless energy and momentum transfers, for the Relativistic Fermi Gas (RFG) and the Super-Scaling approach with relativistic effective mass (SuSAM*) models, within the scaling formalism. In addition, we show that this double differential cross section in the scaling formalism has very good properties to be implemented in the Monte Carlo (MC) neutrino event generators, particularly because its peak is almost flat with the (anti)neutrino energy. This makes it especially well-suited for the event generation by the acceptance-rejection method usually used in the neutrino generators. Finally, we analyze the total charged current quasi-elastic (CCQE) cross section $σ(E_ν)$ for both models and attribute the enhancement observed in the SuSAM* total cross section to the high-momentum components which are present, in a phenomenological way, in its scaling function, while these are absent in the RFG model.

hep-ph↗

arXiv2021

Semiempirical formula for electroweak response functions in the two-nucleon emission channel in neutrino-nucleus scattering

A semi-empirical formula for the electroweak response functions in the two-nucleon emission channel is proposed. The method consists in expanding each one of the vector-vector, axial-axial and vector-axial responses as sums of six sub-responses. These corresponds to separating the meson-exchange currents as the sum of three currents of similar structure, and expanding the hadronic tensor, as the sum of the separate contributions from each current plus the interferences between them. For each sub-response we factorize the coupling constants, the electroweak form factors, the phase space and the delta propagator, for the delta forward current. The remaining spin-isospin contributions are encoded in coefficients for each value of the momentum transfer, $q$. The coefficients are fitted to the exact results in the relativistic mean field model of nuclear matter, for each value of $q$. The dependence on the energy transfer, $ω$ is well described by the semi-empirical formula. The $q$-dependency of the coefficients of the sub-responses can be parameterized or can be interpolated from the provided tables. The description of the five theoretical responses is quite good. The parameters of the formula, the Fermi momentum, number of particles relativistic effective mass, vector energy the electroweak form factors and the coupling constants, can be modified easily. This semi-empirical formula can be applied to the cross-section of neutrinos, antineutrinos and electrons.

nucl-th↗

arXiv2021

Cabibbo suppressed single pion production off the nucleon induced by antineutrinos

In this work we study the $Σπ$ and $Λπ$ production off free nucleons driven by the strangeness-changing weak charged current. We calculate the total cross sections for all possible channels and estimate the flux-averaged total cross sections for experiments like MiniBooNE, SciBooNE, T2K, and Minerva. The model is based on the lowest order effective SU(3) chiral Lagrangians in the presence of an external weak charged current and contains Born and the lowest-lying decuplet resonant mechanisms that can contribute to these reaction channels. We also compare and discuss our results with others following similar and very different approaches.

hep-ph↗

arXiv2021

Deep inelastic (anti)neutrino-nucleus scattering

The present status of the field theoretical model studies of the deep inelastic scattering induced by (anti)neutrino on the nuclear targets in a wide range of Bjorken variable $x$ and four momentum transfer square $Q^2$, has been reviewed~\cite{Haider:2011qs,Haider:2012nf,Haider:2016zrk,Zaidi:2019mfd,Zaidi:2019asc,Ansari:2020xne}. The effect of the nonperturbative corrections such as target mass correction and higher twist effects, perturbative evolution of the parton densities, nuclear medium modifications in the nucleon structure functions, nuclear isoscalarity corrections on the weak nuclear structure functions have been discussed. These structure functions have been used to obtain the differential scattering cross sections. The various nuclear medium effects like the Fermi motion, binding energy, nucleon correlations, mesonic contributions, shadowing and antishadowing corrections relevant in the different regions of $x$ and $Q^2$ have been discussed. The numerical results for the structure functions and the cross sections are compared with some of the available experimental data including the recent results from MINERvA. The predictions are made in argon nuclear target which is planned to be used as a target material in DUNE at the Fermilab.

hep-ph↗

arXiv2021

Neutrino-Nucleus scattering in the SuSA model

The Super-Scaling Approach (SuSA) model, based on the analogies between electron and neutrino interactions with nuclei, is reviewed and its application to the description of neutrino-nucleus scattering is presented. The contribution of both one- and two-body relativistic currents is considered. A selection of results is presented where theoretical predictions are compared with cross section measurements from the main ongoing neutrino oscillation experiments.

hep-ph↗

arXiv2021

Meson-exchange currents and superscaling analysis with relativistic effective mass of quasielastic electron scattering from $^{12}$C

We reanalyze the scaling properties of inclusive quasielastic electron scattering from $^{12}$C by subtracting from the data the effects of two-particle emission. A model of relativistic meson-exchange currents (MEC) is employed within the mean field theory of nuclear matter, with scalar and vector potentials that induce an effective mass and a vector energy to the nucleons. A new phenomenological quasielastic scaling function is extracted from a selection of the data after the subtraction of the 2p-2h contribution. The resulting superscaling approach with relativistic effective mass (SuSAM*) can be used to compute the genuine quasielastic cross section without contamination of the 2p-2h channel that can then be added separately to obtain the total quasielastic plus two-nucleon emission response.

nucl-th↗

arXiv2020

Electron- versus neutrino-nucleus scattering

We illustrate the connection between electron and neutrino scattering off nuclei and show how the former process can be used to constrain the description of the latter. After reviewing some of the nuclear models commonly used to study lepton-nucleus reactions, we describe in detail the SuSAv2 model and show how its predictions compare with the available electron- and neutrino-scattering data over the kinematical range going from the quasi-elastic peak to pion-production and highly inelastic scattering.

nucl-th↗

arXiv2019

Weak structure functions in $ν_l-N$ and $ν_l-A$ scattering with nonperturbative and higher order perturbative QCD effects

We study the effect of various perturbative and nonperturbative QCD corrections on the free nucleon structure functions ($F_{iN}^{WI}(x,Q^2); ~i=1-3$) and their implications in the determination of nuclear structure functions. The evaluation of the nucleon structure functions has been performed by using the MMHT 2014 PDFs parameterization, and the TMC and HT effects are incorporated following the works of Schienbein et al. and Dasgupta et al., respectively. These nucleon structure functions are taken as input in the determination of nuclear structure functions. The numerical calculations for the $ν_l/\barν_l-A$ DIS process have been performed by incorporating the nuclear medium effects like Fermi motion, binding energy, nucleon correlations, mesonic contributions, shadowing and antishadowing in several nuclear targets such as carbon, polystyrene scintillator, iron and lead which are being used in MINERvA, and in argon nucleus which is relevant for the ArgoNeuT and DUNE experiments. The differential scattering cross sections $\frac{d^2σ_A^{WI}}{dx dy}$ and $(\frac{dσ_A^{WI}}{dx}/\frac{dσ_{CH}^{WI}}{dx})$ have also been studied in the kinematic region of MINERvA experiment. The theoretical results are compared with the recent experimental data of MINERvA and the earlier data of NuTeV, CCFR, CDHSW and CHORUS collaborations. Moreover, a comparative analysis of the present results for the ratio $(\frac{dσ_A^{WI}}{dx}/\frac{dσ_{CH}^{WI}}{dx})$, and the results from the MC generator GENIE and other phenomenological models of Bodek and Yang, and Cloet et al., has been performed in the context of MINERvA experiment. The predictions have also been made for $\barν_l-A$ cross section relevant for MINERvA experiment.

hep-ph↗

arXiv2019

Weak production of strange $Ξ$ baryons off the nucleon

The charged current Cabibbo-supressed associated $K Ξ$ production off the nucleon induced by anti-neutrinos is studied at low and intermediate energies. The non-resonant terms are obtained using a microscopical model based on the SU(3) chiral Lagrangian. The basic parameters of the model are $f_π$, the pion decay constant, Cabibbo's angle, the proton and neutron magnetic moments and the axial vector coupling constants for the baryons octet, D and F, that are obtained from the analysis of the semileptonic decays of neutron and hyperons. In addition, we also consider $Σ^\ast(1385)$ resonance, which can decay in $K Ξ$ final state when this channel is open. The studied mechanism is the prime source of $Ξ$ production at anti-neutrino energies around $2$ GeV and the calculated cross sections at these energies can be measured at the current and future neutrino experiments.

hep-ph↗

arXiv2019

Nucleon and nuclear structure functions with non-perturbative and higher order perturbative QCD effects

We have studied the nucleon structure functions $F_{iN}^{EM} (x,Q^2);~i=1,2$, by including contributions due to the higher order perturbative QCD effect up to NNLO and the non-perturbative effects due to the kinematical and dynamical higher twist (HT) effects. The numerical results for $F_{iN}^{EM}(x,Q^2)$ are obtained using Martin, Motylinski, Harland-Lang, Thorne (MMHT) 2014 NLO and NNLO nucleon parton distribution functions (PDFs). The dynamical HT correction has been included following the renormalon approach as well as the phenomenological approach and the kinematical HT effect is incorporated using the works of Schienbein et al. These nucleon structure functions have been used as an input to calculate the nuclear structure functions $F_{iA}^{EM} (x,Q^2)$. In a nucleus, the nuclear corrections arise because of the Fermi motion, binding energy, nucleon correlations, mesonic contribution, shadowing and antishadowing effects. These nuclear corrections are taken into account in the numerical calculations to obtain the nuclear structure functions $F_{iA}^{EM} (x,Q^2)$, for the various nuclear targets like $^{12}C$, $^{27}Al$, $^{56}Fe$, $^{64}Cu$, $^{118}Sn$, $^{197}Au$ and $^{208}Pb$ which are of experimental interest. The effect of isoscalarity correction for nonisoscalar nuclear targets has also been studied. The results for the $F_{iA}^{EM} (x,Q^2)$ are compared with nCTEQ nuclear PDFs parameterization as well as with the experimental results from JLab, SLAC and NMC in the kinematic region of $0.1 \le x \le 0.8$ for several nuclei.

hep-ph↗

arXiv2019

Neutrino-Oxygen CC0$π$ scattering in the SuSAv2-MEC model

We present the predictions of the SuSAv2-MEC model for the double differential charged-current muonic neutrino (antineutrino) cross section on water for the T2K neutrino (antineutrino) beam. We validate our model by comparing with the available inclusive electron scattering data on oxygen and compare our predictions with the recent T2K $ν_μ$-$^{16}$O data, finding good agreement at all kinematics. We show that the results are very similar to those obtained for $ν_μ-^{12}$C scattering, except at low energies, and we comment on the origin of this difference. A factorized spectral function model of $^{16}$O is also included for purposes of comparison.

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