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The determination of the nuclear spectral function from the measured cross section of the electron-nucleus scattering process $e + A \to e^\prime + p + (A-1)$is discussed, and illustrated for the case of a carbon target. The theoretical model based on the local density approximation, previously employed to derive the spectral function from a combination of accurate theoretical calculations and experimental data, has been developed further by including additional information obtained from measurements performed with high missing energy resolution. The implications for the analysis of $\gamma$-ray emission associated with nuclear deexcitation are considered.

We discuss the inclusion of relativistic boost corrections into the CBF effective nuclear Hamiltonian, derived from a realistic model of two- and three-nucleon interactions using the formalism of correlated basis functions and the cluster expansion technique. Different procedures to take into account the effects of boost interactions are compared on the basis of the ability to reproduce the nuclear matter equation of state obtained from accurate many-body calculations. The results of our study show that the repulsive contribution of the boost interaction significantly depends on the underlying model of the non relativistic potential. On the other hand, the dominant relativistic correction turns out to be the corresponding reduction of the strength of repulsive three-nucleon interactions, leading to a significant softening of the equation of state at supranuclear densities., Comment: Few changes to match the version published in Phys. Rev. C

Nuclear many-body theory is based on the tenet that nuclear systems can be accurately described as collections of point-like particles. This picture, while providing a remarkably accurate explanation of a wealth of measured properties of atomic nuclei, is bound to break down in the high-density regime, in which degrees of freedom other than protons and neutrons are expected to come into play. Valuable information on the validity of the description of dense nuclear matter in terms of nucleons, needed to firmly establish its limit of applicability, can be obtained from electron-nucleus scattering data at large momentum transfer and low energy transfer. The emergence of y-scaling in this kinematic region, unambiguously showing that the beam particles couple to high-momentum nucleons belonging to strongly correlated pairs, indicates that at densities as large as five times nuclear density -- typical of the neutron star interior -- nuclear matter largely behaves as a collection of nucleons.

A fully quantitative description of equilibrium and dynamical properties of hot nuclear matter will be needed for the interpretation of the available and forthcoming astrophysical data, providing information on the post merger phase of a neutron star coalescence. We discuss the results of a recently developed theoretical model,based on a phenomenological nuclear Hamiltonian including two- and three-nucleon potentials, to study the temperature dependence of average and single-particle properties of nuclear matter relevant to astrophysical applications. The potential of the proposed approach for describing dissipative processes leading to the appearance of bulk viscosity in neutron star matter is also outlined., Comment: Submitted to Universe for publication in the Special Issue on Many-Body Theory. arXiv admin note: text overlap with arXiv:2208.03131, arXiv:2205.11183

The achievement of the goals of the ongoing and future accelerator-based neutrino experiments - notably the determination of CP violating phase in the lepton sector - will require the development of advanced models of neutrino-nucleus interactions. In this review, we summarise the present status of experimental studies of neutrino-nucleus scattering, and discuss the developments and perspectives of the theoretical approach based on factorisation of the nuclear cross section, which has recently emerged as a promising framework for the description of the variety of processes contributing to the detected signals., Comment: 27 pages, 13 figures, accepted by EPJA

A quantitative description of the properties of hot nuclear matter will be needed for the interpretation of the available and forthcoming astrophysical data, providing information on the post merger phase of a neutron star coalescence. We have employed a recently developed theoretical model, based on a phenomenological nuclear Hamiltonian including two- and three-nucleon potentials, to study the temperature dependence of average and single-particle properties of nuclear matter relevant to astrophysical applications. The possibility to represent the results of microscopic calculations using simple and yet physically motivated parametrisations of thermal effects, suitable for use in numerical simulations of astrophysical processes, is also discussed.

Astrophysical observations of neutron stars have been widely used to infer the properties of the nuclear matter equation of state. Beside being a source of information on average properties of dense matter, however, the data provided by electromagnetic and gravitational wave (GW) facilities are reaching the accuracy needed to constrain, for the first time, nuclear dynamics in dense matter. In this work we assess the sensitivity of current and future neutron star observations to directly infer the strength of repulsive three-nucleon forces, which are key to determine the stiffness of the equation of state. Using a Bayesian approach we focus on the constraints that can be derived on three-body interactions from binary neutron star mergers observed by second and third-generation of gravitational wave interferometers. We consider both single and multiple observations. For current detectors at design sensitivity the analysis suggests that only low mass systems, with large signal-to-noise ratios (SNR), allow to reliably constrain the three-body forces. However, our results show that a single observation with a third-generation interferometer, such as the Einstein Telescope or Cosmic Explorer, will constrain the strength of the repulsive three-body potential with exquisite accuracy, turning third-generation GW detectors into new laboratories to study the nucleon dynamics., Comment: Minor changes to improve the discussion of the results. Technical details added to extend the equation of state description

The interpretation of the available and forthcoming data obtained from multimessenger astrophysical observations -- potentially providing unprecedented access to neutron star properties -- will require the development of novel, accurate theoretical models of dense matter. Of great importance, in this context, will be the capability to devise a description of thermal effects applicable to the study of quantities other than the equation of state, such as the transport coefficients and the neutrino mean free path in the nuclear medium. The formalism based on correlated basis states and the cluster expansion technique has been previously employed to derive a well-behaved effective interaction -- suitable for use in standard perturbation theory -- from a state-of-the-art nuclear Hamiltonian, including phenomenological two- and three-nucleon potentials. Here, we provide a comprehensive and self-contained account of the extension of this approach to the treatment of finite-temperature effects, and report the results of numerical calculations of a number of properties of nuclear matter with arbitrary neutron excess and temperature up to 50 MeV., Comment: 20 pages, 11 figures, typeset using aastex631

The detection of gravitational radiation, emitted in the aftermath of the excitation of neutron star quasi-normal modes, has the potential to provide unprecedented access to the properties of matter in the star interior, and shed new light on the dynamics of nuclear interactions at microscopic level. Of great importance, in this context, will be the sensitivity to themodelling of three-nucleon interactions, which are known to play a critical role in the high-density regime. We report the results of a calculation of the frequencies and damping times of the fundamental mode, carried out using the equation of state of Akmal, Pandharipande and Ravenhall as a baseline, and varying the strength of the isoscalar repulsive term the Urbana IX potential within a range consistent with multimessenger astrophysical observations. The results of our analysis indicate that repulsive three-nucleon interactions strongly affect the stiffness of the equation of state, which in turn determines the pattern of the gravitational radiation frequencies, largely independent of the mass of the source. The observational implications are also discussed.

The interpretation of the nuclear cross sections measured using accelerator neutrino beams involve severe difficulties, arising primarily from the average over the incoming neutrino flux. The broad energy distribution of the beam particles hampers the determination of the energy transfer to the nuclear target, the knowledge of which is needed to pin down the dominant reaction mechanism. Overcoming this problem requires the development of a theoretical approach suitable to describe neutrino interactions at energies ranging from hundreds of MeV to few GeV. In this paper, it is argued that the approach based on the factorisation of the nuclear cross section provides a consistent framework for the calculation of neutrino-nucleus interactions in both the quasi elastic and inelastic channels. The near-degeneracy between theoretical models based on different assumptions, and the use of electron scattering data to advance the understanding of neutrino-nucleus cross sections are also discussed., Comment: Submittted to EPJ Special Topics. arXiv admin note: substantial text overlap with arXiv:1612.01473

We report the results of a study aimed at inferring direct information on the repulsive three-nucleon potential $V^R_{ijk}$\textemdash driving the stiffness of the nuclear matter equation of state at supranuclear densities\textemdash from astrophysical observations. Using a Bayesian approach, we exploit the measurements of masses, radii and tidal deformabalities performed by the NICER satellite and the LIGO/Virgo collaboration, as well as the mass of the heaviest observed pulsar, to constrain the strength of $V^R_{ijk}$. The baseline of our analysis is the widely employed nuclear Hamiltonian comprising the Argonne $v_{18}$ nucleon-nucleon potential andthe Urbana IX model of three-nucleon potential. The numerical results, largely determined by the bound on the maximum mass, suggest that existing and future facilities have the potential to provide valuable new insight into microscopic nuclear dynamics at supranuclear densities., Comment: Discussion of the results extended. Various changes to match the version in press on Phys. Rev. C

The article of Pastore et al, while proposing an interesting and potentially useful approach for the generalisation of Quantum Monte Carlo techniques to the treatment of the nuclear electromagnetic response, features an incorrect and misleading discussion of y-scaling. The response to interactions with transversely polarised virtual photons receives sizeable contributions from non-scaling processes, in which the momentum transfer is shared between two nucleons. It follows that, contrary to what is stated by the the authors, y-scaling in the transverse channel is accidental.

Experimental studies of hypernuclear dynamics, besides being essential for the understanding of strong interactions in the strange sector, have important astrophysical implications. The observation of neutron stars with masses exceeding two solar masses poses a serious challenge to the models of hyperon dynamics in dense nuclear matter, many of which predict a maximum mass incompatible with the data. In this article, it is argued that valuable new insight may be gained extending the experimental studies of kaon electro production from nuclei to include the $\isotope[208][]{\rm Pb}(e,e^\prime K^+) \isotope[208][\Lambda]{\rm Tl}$ process. The connection with proton knockout reactions and the availability of accurate $\isotope[208][]{\rm Pb}(e,e^\prime p) \isotope[207][]{\rm Tl}$ data can be exploited to achieve a largely model-independent analysis of the measured cross section. A framework for the description of kaon electro production based on the formalism of nuclear many-body theory is outlined., Comment: Revised version, to be published in "Particles"

The observation of the gravitational wave signal GW170817, consistent with emission from the inspiral of a binary neutron-star system, provided information on the tidal deformation of the participating stars. The available data may be exploited to constrain the equation of state of densenuclear matter, as well as to shed light on the underlying models describing nuclear dynamics at microscopic level. In this paper we compare the experimental results to the predictions of different theoretical models, based on non relativistic nuclear many-body theory, the relativistic field-theoretical formalism, and a more phenomenological approach constrained by observed nuclear properties. While the precision of the available data does not allow to resolve the degeneracy of the models, our analysis shows a distinct sensitivity to the star compactness predicted by the different equations of state, which turns out to be significantly affected by relativistic boost corrections to the nucleon-nucleon potential., Comment: Accepted for publication in Physical Review C

The scale-dependence of the nucleon-nucleon interaction, which in recent years has been extensively analysed within the context of chiral effective field theory, is, in fact, inherent in any potential models constrained by a fit to scattering data. A comparison between a purely phenomenological potential and local interactions derived from chiral effective field theory suggests that--thanks to the ability to describe nucleon-nucleon scattering at higher energies, as well as the deuteron momentum distribution extracted from electro-disintegration data--phenomenological potentials are best suited for the description of nuclear dynamics at the scale relevant to neutron star matter.

With the discovery of non-zero value of $\theta_{13}$ mixing angle, the next generation of long-baseline neutrino (LBN) experiments offers the possibility of obtaining statistically significant samples of muon and electron neutrinos and anti-neutrinos with large oscillation effects. In this document we intend to highlight the importance of Near Detector facilities in LBN experiments to both constrain the systematic uncertainties affecting oscillation analyses but also to perform, thanks to their close location, measurements of broad benefit for LBN physics goals. A strong European contribution to these efforts is possible., Comment: Document submitted to the European Strategy For European Particle Physics

The factorization scheme, based on the impulse approximation and the spectral function formalism, has been recently generalized to allow the description of electromagnetic nuclear interactions driven by two-nucleon currents. We have extended this framework to the case of weak charged and neutral currents and carried out calculations of the double-differential neutrino-carbon and neutrino-oxygen cross sections using two different models of the target spectral functions. The results, showing a moderate dependence on the input spectral function, confirm that our approach provides a consistent treatment of all reaction mechanisms contributing to the signals detected by accelerator-based neutrino experiments., Comment: 18 pages, 7 figures

We develop an innovative technique for studying inhomogeneous phases with a spontaneous broken symmetry. The method relies on the knowledge of the exact form of the free energy in the homogeneous phase and on a specific gradient expansion of the order parameter. We apply this method to quark matter at vanishing temperature and large chemical potential, which is expected to be relevant for astrophysical considerations. The method is remarkably reliable and fast as compared to performing the full numerical diagonalization of the quark Hamiltonian in momentum space, and is designed to improve the standard Ginzburg-Landau expansion close to the phase transition points. For definiteness we focus on inhomogeneous chiral symmetry breaking, accurately reproducing known results for 1D and 2D modulations and examining novel crystalline structures, as well. Consistently with previous results, we find that the energetically favored modulation is the so-called 1D real kink crystal. We propose a qualitative description of the pairing mechanism to motivate this result., Comment: 11 pages, 8 figures. v2 with minor changes. Accepted for publication on Physical Review D

An updated and improved version of the effective interaction based on the Argonne\textendash Urbana nuclear Hamiltonian\textemdash derived using the formalism of Correlated Basis Functions (CBF) and the cluster expansion technique\textemdash is employed to obtain a number of properties of cold nuclear matter at arbitrary neutron excess within the formalism of many-body perturbation theory. The numerical results\textemdash including the ground-state energy per nucleon, the symmetry energy, the pressure, the compressibility, and the single-particle spectrum\textemdash are discussed in the context of the available empirical information, obtained from measured nuclear properties and heavy-ion collisions.

Correlated Basis Function (CBF) perturbation theory and the formalism of cluster expansions have been recently employed to obtain an effective interaction from a nuclear Hamiltonian strongly constrained by phenomenology. We report the results of a study of the superfluid gap in pure neutron matter, associated with the formation of Cooper pairs in the $^1S_0$ channel. The calculations have been carried out using an improved version of the CBF effective interaction, in which three-nucleon forces are taken into account using a microscopic model. Our results show that a non-vanishing superfluid gap develops at densities in the range $2 \times 10^{-4} \lesssim \rho/\rho_0 \lesssim 0.1 $, where $\rho_0 = 2.8 \times 10^{14}$ g cm$^{-3}$ is the equilibrium density of isospin-symmetric nuclear matter, corresponding mainly to the neutron star inner crust., Comment: 13 pages, 5 figures. arXiv admin note: substantial text overlap with arXiv:1305.4659

In a core-collapse supernova, a huge amount of energy is released in the Kelvin-Helmholtz phase subsequent to the explosion, when the proto-neutron star cools and deleptonizes as it loses neutrinos. Most of this energy is emitted through neutrinos, but a fraction of it can be released through gravitational waves. We model the evolution of a proto-neutron star in the Kelvin-Helmholtz phase using a general relativistic numerical code, and a recently proposed finite temperature, many-body equation of state; from this we consistently compute the diffusion coefficients driving the evolution. To include the many-body equation of state, we develop a new fitting formula for the high density baryon free energy at finite temperature and intermediate proton fraction. We estimate the emitted neutrino signal, assessing its detectability by present terrestrial detectors, and we determine the frequencies and damping times of the quasi-normal modes which would characterize the gravitational wave signal emitted in this stage., Comment: 25 pages, 14 figures, accepted by PRD

We report the results of a study of neutrino-carbon interactions at beam energies ranging between few hundreds MeV and few tens of GeV, carried out within the framework of the impulse approximation using a realistic spectral function. The contributions of quasi elastic scattering, resonance production and deep inelastic scattering---consistently obtained, for first time, from a model based on a realistic description of the nuclear ground state---are compared and analyzed.

I discuss the near-degeneracy between models of neutrino-nucleus interactions based on diverse assumptions, and analyze a specific example illustrating how the different reaction mechanisms taken into account, as well as the approximations associated with their implementation, may conspire to make the prediction of two models look similar. I argue that the relevant reaction mechanisms may be unambiguously identified exploiting the availability of electron-nucleus scattering data other than inclusive cross sections, providing detailed information on the nuclear spectral function.

The electromagnetic responses of carbon obtained from the Green's function Monte Carlo and spectral function approaches using the same dynamical input are compared in the kinematical region corresponding to momentum transfer in the range 300-570 MeV. The results of our analysis, aimed at pinning down the limits of applicability of the approximations involved in the two schemes, indicate that the factorization ansatz underlying the spectral function formalism provides remarkably accurate results down to momentum transfer as low as 300 MeV. On the other hand, it appears that at 570 MeV relativistic corrections to the electromagnetic current not included in the Monte Carlo calculations may play a significant role in the transverse channel., Comment: 8 pages, 6 figures

The DUNE/LBNF program aims to address key questions in neutrino physics and astroparticle physics. Realizing DUNE's potential to reconstruct low-energy particles in the 10-100 MeV energy range will bring significant benefits for all DUNE's science goals. In neutrino physics, low-energy sensitivity will improve neutrino energy reconstruction in the GeV range relevant for the kinematics of DUNE's long-baseline oscillation program. In astroparticle physics, low-energy capabilities will make DUNE's far detectors the world's best apparatus for studying the electron-neutrino flux from a supernova. This will open a new window to unrivaled studies of the dynamics and neutronization of a star's central core in real time, the potential discovery of the neutrino mass hierarchy, provide new sensitivity to physics beyond the Standard Model, and evidence of neutrino quantum-coherence effects. The same capabilities will also provide new sensitivity to `boosted dark matter' models that are not observable in traditional direct dark matter detectors., Comment: Summary of workshop "Supernova Physics at DUNE" held at Virginia Tech; for more details, see, http://cnp.phys.vt.edu/SNatDUNE/

We report the results of a study aimed at quantifying the impact on the oscillation analysis of the uncertainties associated with the description of the neutrino-nucleus cross section in the two-particle--two-hole sector. The results of our calculations, based on the kinematic method of energy reconstruction and carried out comparing two data-driven approaches, show that the existing discrepancies in the neutrino cross sections have a sizable effect on the extracted oscillation parameters, particularly in the antineutrino channel., Comment: 7 pages, 5 figures