Alessandro Lovato

Electromagnetic and neutral-weak response functions of He 4 and C 12

Ab initio calculations of the quasi-elastic electromagnetic and neutral-weak response functions of 4He and 12C are carried out for the first time. They are based on a realistic approach to nuclear dynamics, in which the strong interactions are described by two- and three-nucleon potentials and the electroweak interactions with external fields include one- and two-body terms. The Greens function Monte Carlo method is used to calculate directly the Laplace transforms of the response functions, and maximum-entropy techniques are employed to invert the resulting imaginary-time correlation functions with associated statistical errors. The theoretical results, confirmed by experiment in the electromagnetic case, show that two-body currents generate excess transverse strength from threshold to the quasi-elastic to the dip region and beyond. These findings challenge the conventional picture of quasi-elastic inclusive scattering as being largely dominated by single-nucleon knockout processes.

Neutral weak-current two-body contributions in inclusive scattering from {sup 12}C

An ab initio calculation of the sum rules of the neutral weak response functions in 12C is reported, based on a realistic Hamiltonian, including two- and three-nucleon potentials, and on realistic currents, consisting of one- and two-body terms. We find that the sum rules of the response functions associated with the longitudinal and transverse components of the (spacelike) neutral current are largest and that a significant portion (≃30%) of the calculated strength is due to two-body terms. This fact may have implications for the MiniBooNE and other neutrino quasielastic scattering data on nuclei.

Unified Description of Electron-Nucleus Scattering within the Spectral Function Formalism

The formalism based on factorization and nuclear spectral functions has been generalized to treat transition matrix elements involving two-nucleon currents, whose contribution to the nuclear electromagnetic response in the transverse channel is known to be significant. We report the results of calculations of the inclusive electron-carbon cross section, showing that the inclusion of processes involving two-nucleon currents appreciably improves the agreement between theory and data in the dip region, between the quasielastic and Δ-production peaks. The relation to approaches based on the independent particle of the nucleus and the implications for the analysis of flux-integrated neutrino-nucleus cross sections are discussed.

Local chiral potentials with Δ -intermediate states and the structure of light nuclei

We present fully local versions of the minimally non-local nucleon-nucleon potentials constructed in a previous paper [M. Piarulli et al., Phys. Rev. C 91, 024003 (2015)], and use them in hypersperical-harmonics and quantum Monte Carlo calculations of ground and excited states of 3H, 3He, 4He, 6He, and 6Li nuclei. The long-range part of these local potentials includes oneand two-pion exchange contributions without and with ∆-isobars in the intermediate states up to order Q3 (Q denotes generically the low momentum scale) in the chiral expansion, while the short-range part consists of contact interactions up to order Q4. The low-energy constants multiplying these contact interactions are fitted to the 2013 Granada database in two different ranges of laboratory energies, either 0–125 MeV or 0–200 MeV, and to the deuteron binding energy and nn singlet scattering length. Fits to these data are performed for three models characterized by longand short-range cutoffs, RL and RS respectively, ranging from (RL, RS) = (1.2, 0.8) fm down to (0.8, 0.6) fm. The long-range (short-range) cutoff regularizes the oneand two-pion exchange (contact) part of the potential. PACS numbers: 21.30.-x, 21.45.-v 1 ar X iv :1 60 6. 06 33 5v 1 [ nu cl -t h] 2 0 Ju n 20 16

Contribution of two-particle–two-hole final states to the nuclear response

The excitation of two particle-two hole final states in neutrino-nucleus scattering has been advocated by many authors as the source of the excess cross section observed by the MiniBooNE Collaboration in the quasi elastic sector. We analyse the mechanisms leading to the appearance of these final states, and illustrate their significance through the results of accurate calculations of the nuclear electromagnetic response in the transverse channel. A novel approach, allowing for a consistent treatment of the amplitudes involving one- and two-nucleon currents in the kinematical region in which the non relativistic approximation breaks down, is outlined.

Variational Calculation of the Ground State of Closed-Shell Nuclei Up to

Variational calculations of ground-state properties of

A

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= 40

He,

Neutral-current interactions of low-energy neutrinos in dense neutron matter

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Evolution of a proto-neutron star with a nuclear many-body equation of state: Neutrino luminosity and gravitational wave frequencies

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