Search

31 pags., 7 figs., The PTOLEMY project aims to develop a scalable design for a Cosmic Neutrino Background (CNB) detector, the first of its kind and the only one conceived that can look directly at the image of the Universe encoded in neutrino background produced in the first second after the Big Bang. The scope of the work for the next three years is to complete the conceptual design of this detector and to validate with direct measurements that the non-neutrino backgrounds are below the expected cosmological signal. In this paper we discuss in details the theoretical aspects of the experiment and its physics goals. In particular, we mainly address three issues. First we discuss the sensitivity of PTOLEMY to the standard neutrino mass scale. We then study the perspectives of the experiment to detect the CNB via neutrino capture on tritium as a function of the neutrino mass scale and the energy resolution of the apparatus. Finally, we consider an extra sterile neutrino with mass in the eV range, coupled to the active states via oscillations, which has been advocated in view of neutrino oscillation anomalies. This extra state would contribute to the tritium decay spectrum, and its properties, mass and mixing angle, could be studied by analyzing the features in the beta decay electron spectrum., Work supported by the Italian grant 2017W4HA7S “NAT-NET: Neutrino and Astroparticle Theory Network” (PRIN 2017) funded by the Italian Ministero dell’Istruzione, dell’Università e della Ricerca (MIUR); by the Spanish grants ENE2016-76755-R, SEV-2014-0398 and FPA2017- 85216-P (AEI/FEDER, UE), PROMETEO/2018/165 (Generalitat Valenciana), María de Maeztu Unit of Excellence CIEMAT - Particle Physics (MDM-2015-0509) and the Red Consolider MultiDark FPA2017-90566-REDC; by the Vetenskapsrådet (Swedish Research Council) through contract No. 638-2013-8993; by the Simons Foundation, USA (#377485) and John Templeton Foundation, USA (#58851); and by the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie individual Grant Agreement No. 796941.

We present the results of a recent simultaneous study of the muon capture reactions 2 H(μ - ,vμ)nn and 3 He(μ - ,vμ) 3 H. The initial and final A = 2 and 3 nuclear wave functions are obtained from the Argonne v18 or chiral N3LO twonucleon potential, in combination with, respectively, the Urbana IX or chiral N2LO three-nucleon potential in the case of A = 3. The weak current consists of polar- and axial-vector components. The former are related to the isovector piece of the electromagnetic current via the conserved-vector-current hypothesis. These and the axial currents are derived either in a meson-exchange or in a chiral e_ective field theory ( x EFT) framework. In the first case, the only parameter is in the axial-vector current and is fixed by reproducing the experimental Gamow-Teller matrix element in tritium _-decay (GT EXP ). In the second case, the low-energy constants, two in the polar and one in the axial-vector current, are fixed, respectively, by reproducing the A = 3 magnetic moments and GTEXP. The total rates are found to be 392.0±2.3 s -1 for A = 2, and 1484 ± 13 s -1 for A = 3, where the spread accounts for the model dependence relative to the adopted interactions and currents and to cuto_ sensitivity in the x EFT currents. These values are compared with available experimental data and results of previous calculations.

The results of a new calculation of the astrophysical S-factor for the proton weak capture on 3He are here reviewed. The methods used to obtain very accurate initial and final state wave functions and to construct the nuclear weak current operator are described. Finally the implications of these results for the Super-Kamiokande solar neutrino data are discussed., Comment: 10 pages, 1 figure, XVII European Few-Body plenary talk, Evora, September 2000

We call "projectile fragmentation" of neutron halo nuclei the elastic breakup (diffraction) reaction, when the observable studied is the neutron-core relative energy spectrum. This observable has been measured in relation to the Coulomb breakup on heavy target and recently also on light targets. Such data enlighten the effect of the neutron final state interaction with the core of origin. Projectile fragmentation is studied here by a time dependent model for the excitation of a nucleon from a bound state to a continuum resonant state in a neutron-core complex potential which acts as a final state interaction. The final state is described by an optical model S-matrix so that both resonant and non resonant states of any continuum energy can be studied as well as deeply bound initial states. It turns out that due to the coupling between the initial and final states, the neutron-core free particle phase shifts are modified, in the exit channel, by an additional phase. Some typical numerical calculations for the relevant observables are presented and compared to experimental data. It is suggest that the excitation energy spectra of an unbound nucleus might reflect the structure of the parent nucleus from whose fragmentation they are obtained., Proceedings of the 11th Conference on Problems in Theoretican Nuclear Physics, Cortona, Italy, 2006. World Scientific

We present an exploratory study consisting in the formulation of a relativistic quantum mechanics to describe the few-nucleon system at low energy, starting from the quantum field theoretical chiral Lagrangian involving pions and nucleons. To this aim we construct a Bakamjian-Thomas mass operator and perform a truncation of the Fock space which respects at each stage the relativistic covariance. Such truncation is justified, at sufficiently low energy, in the framework of a systematic chiral expansion. As an illustration we discuss the low-energy phaseshifts of the nucleon-nucleon and pion-nucleon scattering.

International audience; We study the pygmy resonances in Sn isotopes within a microscopic multiphonon approach which has been successfully applied to heavy ion reactions in recent years. In the energy region of the pygmy resonances there are a few low lying multiphonon states. The question is whether they may contribute to the observed peak. Calculations show that the inelastic cross sections in the relevant energy region have a conisderable increase depending on the isotope and on the kind of Skyrme force used.

The contribution of isospin admixtures in the ground state of the He-4 nucleus is studied using wave functions derived from the most modern nuclear interactions, including isospin symmetry breaking terms. The present calculations show that this contribution is larger than previous estimates had indicated. Its effect on parity violating elastic scattering of polarized electrons from He-4 is investigated. In particular, a simple analysis of the recently measured left-right asymmetry at low Q^2 shows that the contribution of these isospin admixtures is of comparable magnitude to that associated with strangeness components in the nucleon electric form factor.