13 results on '"Alessandro Lovato"'
Search Results
2. Nuclear energy density functionals grounded in ab initio calculations
- Author
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F. Marino, Xavier Roca-Maza, C. Barbieri, A. Carbone, Alessandro Lovato, Gianluca Colò, Francesco Pederiva, and E. Vigezzi
- Subjects
Physics ,Nuclear Theory ,010308 nuclear & particles physics ,Binding energy ,Ab initio ,FOS: Physical sciences ,Charge (physics) ,7. Clean energy ,01 natural sciences ,Nuclear Theory (nucl-th) ,Auxiliary field ,Ab initio quantum chemistry methods ,Quantum mechanics ,0103 physical sciences ,Diffusion Monte Carlo ,Density functional theory ,Local-density approximation ,010306 general physics - Abstract
We discuss the construction of a nuclear Energy Density Functional (EDF) from ab initio calculations, and we advocate the need of a methodical approach that is free from ad hoc assumptions. The equations of state (EoS) of symmetric nuclear and pure neutron matter are computed using the chiral NNLO$_{\rm sat}$ and the phenomenological AV4$^\prime$+UIX$_{c}$ Hamiltonians as inputs in the Self-consistent Green's Function (SCGF) and Auxiliary Field Diffusion Monte Carlo (AFDMC) methods, respectively. We propose a convenient parametrization of the EoS as a function of the Fermi momentum and fit it on the SCGF and AFDMC calculations. We apply the ab initio-based EDF to carry out an analysis of the binding energies and charge radii of different nuclei in the local density approximation. The NNLO$_{\rm sat}$-based EDF produces encouraging results, whereas the AV4$^\prime$+UIX$_{c}$-based one is farther from experiment. Possible explanations of these different behaviors are suggested, and the importance of gradient and spin-orbit terms is analyzed. Our work paves the way for a practical and systematic way to merge ab initio nuclear theory and DFT, while at the same time it sheds light on some of the critical aspects of this procedure., Comment: 14 pages, 6 figures
- Published
- 2021
3. New approach to intranuclear cascades with quantum Monte Carlo configurations
- Author
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Pedro A. N. Machado, Alessandro Lovato, Noemi Rocco, Joshua Isaacson, and William I. Jay
- Subjects
Physics ,010308 nuclear & particles physics ,Scattering ,Quantum Monte Carlo ,Nuclear Theory ,Semiclassical physics ,Observable ,Cascade algorithm ,01 natural sciences ,symbols.namesake ,Pauli exclusion principle ,0103 physical sciences ,symbols ,Probability distribution ,Neutron ,Statistical physics ,Nuclear Experiment ,010306 general physics - Abstract
We propose a novel semiclassical approach to intranuclear cascades, which takes as input quantum Monte Carlo nuclear configurations and uses a semiclassical, impact-parameter-based algorithm to model the propagation of protons and neutrons in the nuclear medium. We successfully compare our simulations to available proton-carbon scattering data and nuclear-transparency measurements. By analyzing the dependence of the simulated observables upon the ingredients entering our intranuclear cascade algorithm, we provide a quantitative understanding of their impact. Particular emphasis is devoted to the role played by nuclear correlations, the Pauli exclusion principle, and interaction probability distributions.
- Published
- 2021
4. Muon capture in nuclei: An ab initio approach based on Green's function Monte Carlo methods
- Author
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Alessandro Lovato, Rocco Schiavilla, and Noemi Rocco
- Subjects
Physics ,Mass number ,Particle physics ,Muon ,010308 nuclear & particles physics ,Nuclear Theory ,Monte Carlo method ,Ab initio ,01 natural sciences ,Muon capture ,0103 physical sciences ,Sensitivity (control systems) ,010306 general physics ,Nucleon ,Random phase approximation - Abstract
An ab initio Green's function Monte Carlo (GFMC) method is introduced for calculating total rates of muon weak capture in light nuclei with mass number $A\ensuremath{\le}12$. As a first application of the method, we perform a calculation of the rate in $^{3}\mathrm{H}$ and $^{4}\mathrm{He}$ in a dynamical framework based on realistic two- and three-nucleon interactions and realistic nuclear charge-changing weak currents. The currents include one- and two-body terms induced by $\ensuremath{\pi}$- and $\ensuremath{\rho}$-meson exchange, and $N$-to-$\mathrm{\ensuremath{\Delta}}$ excitation, and are constrained to reproduce the empirical value of the Gamow-Teller matrix element in tritium. We investigate the sensitivity of theoretical predictions to current parametrizations of the nucleon axial and induced pseudoscalar form factors as well as to two-body contributions in the weak currents. The large uncertainties in the measured $^{4}\mathrm{He}$ rates obtained from bubble-chamber experiments (carried out over 50 years ago) prevent us from drawing any definite conclusions. No data exist for $^{3}\mathrm{H}$, but results are compared to those of a recent Faddeev calculation as a validation of the present GFMC method.
- Published
- 2019
5. Relativistic effects in ab initio electron-nucleus scattering
- Author
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Alessandro Lovato, Noemi Rocco, Giuseppina Orlandini, and Winfried Leidemann
- Subjects
Physics ,Nuclear Theory ,010308 nuclear & particles physics ,Scattering ,Momentum transfer ,Ab initio ,FOS: Physical sciences ,Electron ,01 natural sciences ,Imaging phantom ,High Energy Physics - Experiment ,Nuclear Theory (nucl-th) ,High Energy Physics - Experiment (hep-ex) ,medicine.anatomical_structure ,Quantum mechanics ,0103 physical sciences ,medicine ,010306 general physics ,Relativistic quantum chemistry ,Nuclear theory ,Nucleus - Abstract
The electromagnetic responses obtained from Green's function Monte Carlo (GFMC) calculations are based on realistic treatments of nuclear interactions and currents. The main limitations of this method comes from its nonrelativistic nature and its computational cost, the latter hampering the direct evaluation of the inclusive cross sections as measured by experiments. We extend the applicability of GFMC in the quasielastic region to intermediate momentum transfers by performing the calculations in a reference frame that minimizes nucleon momenta. Additional relativistic effects in the kinematics are accounted for employing the two-fragment model. In addition, we developed a novel algorithm, based on the concept of first-kind scaling, to compute the inclusive electromagnetic cross section of $^4$He through an accurate and reliable interpolation of the response functions. A very good agreement is obtained between theoretical and experimental cross sections for a variety of kinematical setups. This offers a promising prospect for the data analysis of neutrino-oscillation experiments that requires an accurate description of nuclear dynamics in which relativistic effects are fully accounted for., 10 pages, 7 figures
- Published
- 2018
6. Scaling within the spectral function approach
- Author
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Juan Nieves, J. E. Sobczyk, Alessandro Lovato, and Noemi Rocco
- Subjects
Physics ,Nuclear Theory ,010308 nuclear & particles physics ,media_common.quotation_subject ,Momentum transfer ,Electroweak interaction ,FOS: Physical sciences ,Nuclear matter ,01 natural sciences ,Asymmetry ,High Energy Physics - Experiment ,Nuclear Theory (nucl-th) ,Many-body problem ,High Energy Physics - Experiment (hep-ex) ,0103 physical sciences ,Quasiparticle ,Statistical physics ,Nuclear Experiment (nucl-ex) ,Neutrino ,Nuclear Experiment ,010306 general physics ,Scaling ,media_common - Abstract
Scaling features of the nuclear electromagnetic response functions unveil aspects of nuclear dynamics that are crucial for interpretating neutrino- and electron-scattering data. In the large momentum-transfer regime, the nucleon-density response function defines a universal scaling function, which is independent of the nature of the probe. In this work, we analyze the nucleon-density response function of $^{12}$C, neglecting collective excitations. We employ particle and hole spectral functions obtained within two distinct many-body methods, both widely used to describe electroweak reactions in nuclei. We show that the two approaches provide compatible nucleon-density scaling functions that for large momentum transfers satisfy first-kind scaling. Both methods yield scaling functions characterized by an asymmetric shape, although less pronounced than that of experimental scaling functions. This asymmetry, only mildly affected by final state interactions, is mostly due to nucleon-nucleon correlations, encoded in the continuum component of the hole SF., 15 pages, 11 figures
- Published
- 2018
7. Quantum Monte Carlo calculation of neutral-current ν−C12 inclusive quasielastic scattering
- Author
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Ewing Lusk, Steven C. Pieper, Alessandro Lovato, Rocco Schiavilla, J. Carlson, and Stefano Gandolfi
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Physics ,Quasielastic scattering ,Neutral current ,010308 nuclear & particles physics ,Scattering ,Quantum Monte Carlo ,High Energy Physics::Phenomenology ,Monte Carlo method ,Inelastic scattering ,01 natural sciences ,Nuclear physics ,Computational chemistry ,0103 physical sciences ,CP violation ,High Energy Physics::Experiment ,Neutrino ,Nuclear Experiment ,010306 general physics - Abstract
Quasielastic neutrino scattering is an important aspect of the experimental program to study fundamental neutrino properties including neutrino masses, mixing angles, mass hierarchy, and charge-conjugation parity (CP)- violating phase. Proper interpretation of the experiments requires reliable theoretical calculations of neutrino-nucleus scattering. In this paper we present calculations of response functions and cross sections by neutral-current scattering of neutrinos off $^{12}\mathrm{C}$. These calculations are based on realistic treatments of nuclear interactions and currents, the latter including the axial, vector, and vector-axial interference terms crucial for determining the difference between neutrino and antineutrino scattering and the CP-violating phase. We find that the strength and energy dependence of two-nucleon processes induced by correlation effects and interaction currents are crucial in providing the most accurate description of neutrino-nucleus scattering in the quasielastic regime.
- Published
- 2018
8. Electromagnetic scaling functions within the Green's function Monte Carlo approach
- Author
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Juan Nieves, Noemi Rocco, Alessandro Lovato, and Luis Alvarez-Ruso
- Subjects
Physics ,Current (mathematics) ,Nuclear Theory ,010308 nuclear & particles physics ,media_common.quotation_subject ,Monte Carlo method ,FOS: Physical sciences ,Function (mathematics) ,01 natural sciences ,Asymmetry ,High Energy Physics - Experiment ,Nuclear Theory (nucl-th) ,High Energy Physics - Experiment (hep-ex) ,symbols.namesake ,Transverse plane ,Zeroth law of thermodynamics ,Green's function ,Quantum mechanics ,0103 physical sciences ,symbols ,010306 general physics ,Scaling ,media_common - Abstract
We have studied the scaling properties of the electromagnetic response functions of $^4$He and $^{12}$C nuclei computed by the Green's Function Monte Carlo approach, retaining only the one-body current contribution. Longitudinal and transverse scaling functions have been obtained in the relativistic and non relativistic cases and compared to experiment for various kinematics. The characteristic asymmetric shape of the scaling function exhibited by data emerges in the calculations in spite of the non relativistic nature of the model. The results are consistent with scaling of zeroth, first and second kinds. Our analysis reveals a direct correspondence between the scaling and the nucleon-density response functions., 11 pages, 15 figures
- Published
- 2017
9. Comparison of the electromagnetic responses of C12 obtained from the Green's function Monte Carlo and spectral function approaches
- Author
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Alessandro Lovato, Omar Benhar, and Noemi Rocco
- Subjects
Physics ,010308 nuclear & particles physics ,Quantum Monte Carlo ,Momentum transfer ,Monte Carlo method ,Function (mathematics) ,01 natural sciences ,symbols.namesake ,Green's function ,Quantum electrodynamics ,0103 physical sciences ,symbols ,Diffusion Monte Carlo ,010306 general physics ,Hamiltonian (quantum mechanics) ,Ansatz - Abstract
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.
- Published
- 2016
10. Contribution of two-particle–two-hole final states to the nuclear response
- Author
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Noemi Rocco, Omar Benhar, and Alessandro Lovato
- Subjects
Physics ,Nuclear and High Energy Physics ,Nuclear Theory ,Scattering ,Many-body theory ,FOS: Physical sciences ,Nuclear Theory (nucl-th) ,Nuclear physics ,MiniBooNE ,Transverse plane ,Cross section (physics) ,Amplitude ,Particle ,Nuclear Experiment ,Excitation - Abstract
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., Comment: Physical Review C, in press. arXiv admin note: text overlap with arXiv:1312.1210
- Published
- 2015
11. Electromagnetic and neutral-weak response functions ofHe4andC12
- Author
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Alessandro Lovato, Rocco Schiavilla, Steven C. Pieper, J. Carlson, and Stefano Gandolfi
- Subjects
Physics ,Nuclear and High Energy Physics ,Scattering ,Quantum electrodynamics ,Quantum mechanics ,Quantum Monte Carlo ,Physics::Medical Physics ,Electroweak interaction ,Nuclear theory ,Imaging phantom ,Neutrino scattering - Abstract
The authors calculate $a\phantom{\rule{0}{0ex}}b$-$i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}o$ quasi-elastic electromagnetic and neutral-weak response functions for $A=4$ and $A=12$ nuclei by using realistic nuclear two- and three-body forces and one- and two-body electroweak currents, in combination with quantum Monte Carlo methods and maximum-entropy techniques. In the electromagnetic case, their novel approach allows a direct comparison with experimental data. The results challenge the conventional picture that quasi-elastic inclusive scattering is dominated by single-nucleon knockout.
- Published
- 2015
12. Effective-interaction approach to the Fermi hard-sphere system
- Author
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Alessandro Lovato, Artur Polls, Angela Mecca, and Omar Benhar
- Subjects
Physics ,Nuclear and High Energy Physics ,Nuclear Theory ,Many-body theory ,FOS: Physical sciences ,Basis function ,Nuclear matter ,Nuclear Theory (nucl-th) ,Formalism (philosophy of mathematics) ,symbols.namesake ,Effective mass (solid-state physics) ,Classical mechanics ,Quantum Gases (cond-mat.quant-gas) ,symbols ,Statistical physics ,Condensed Matter - Quantum Gases ,Hamiltonian (quantum mechanics) ,Nuclear theory ,Fermi Gamma-ray Space Telescope - Abstract
The formalism based on correlated basis functions and the cluster expansion technique has been recently employed to derive an effective interaction from a realistic nuclear hamiltonian. To gauge the reliability of this scheme, we perform a systematic comparison between the results of its application to the Fermi hard-sphere system and the predictions obtained from low-density expansions, as well as from other many-body techniques. The analysis of a variety of properties, including the ground state energy, the effective mass and the momentum distribution, shows that the effective interaction approach is remarkably accurate, thus suggesting that it may be employed to achieve a consistent description of the structure and dynamics of nuclear matter in the density region relevant to astrophysical applications., Comment: 10 pages, 13 figures
- Published
- 2015
13. Comparative study of three-nucleon potentials in nuclear matter
- Author
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Stefano Fantoni, Kevin Schmidt, Alessandro Lovato, and Omar Benhar
- Subjects
Physics ,Nuclear and High Energy Physics ,Equation of state ,Nuclear Theory ,010308 nuclear & particles physics ,Binding energy ,FOS: Physical sciences ,Scattering length ,Nuclear matter ,01 natural sciences ,Nuclear Theory (nucl-th) ,Auxiliary field ,Astrophysics - Solar and Stellar Astrophysics ,Quantum mechanics ,0103 physical sciences ,Diffusion Monte Carlo ,Neutron ,Nuclear Experiment ,010306 general physics ,Nucleon ,Solar and Stellar Astrophysics (astro-ph.SR) - Abstract
A new generation of local three-body potentials providing an excellent description of the properties of light nuclei, as well as of the neutron-deuteron doublet scattering length, has been recently derived. We have performed a comparative analysis of the equations of state of both pure neutron matter and symmetric nuclear matter obtained using these models of three-nucleon forces. None of the considered potentials simultaneously explains the empirical equilibrium density and binding energy of symmetric nuclear matter. However, two of them provide reasonable values of the saturation density. The ambiguity concerning the treatment of the contact term of the chiral inspired potentials is discussed., Comment: 14 pages, 8 figures
- Published
- 2012
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