Μελέτη Αστροφυσικών Νετρίνων Με Τεχνικές Προσομοίωσης Και Υπολογισμούς Πυρηνικής Δομής

Abstract

Study of astrophysical neutrinoswith simulation techniques and nuclear structure calculations by: Vaitsa Tsakstara In the present Thesis, we investigated low and intermediate energy astrophysical neutrinos, by performing nuclear structure calculations and employing modern simulation techniques. One of our main goals, was to explore the nuclear response to supernova neutrino energy spectra of various nuclear detectors used recently in terrestrial experiments searching for events of rare process, like the neutrinoless double beta decay, that take place in the presence of nuclei.We concentrated on the systematic studies of the neutrino-nucleus reactions 64,66 Zn(ν, ν ′ ) 64,66 Zn * and 128,130 T e(ν, ν ′ ) 128,130 T e * , as well as the antineutrinonucleus reactions 64,66 Zn( ν, ν ′ ) 64,66 Zn * and 128,130 T e( ν, ν ′ ) 128,130 T e * . The nuclei T e and Zn, are contents of the CdZnT e and CdT e semi-conductors, which are promising detectors of the COBRA double beta decay experiment at Gran Sasso.From a nuclear structure calculations point of view, the original (anti)neutrinonucleus reaction cross sections are evaluated within the context of the quasiparticle random phase approximation (QRPA), by utilizing realistic two-body forces for the strong nucleon-nucleon interaction. We restricted ourselves to the neutral current (anti)neutrino-nucleus reactions, assuming an effective Hamiltonian for the description of the weak interaction between the incoming neutrino and the nuclear target constructed in the framework of the current-current interaction hypothesis, i.e. written as a product of the leptonic times the hadronic (nuclear) current.The detailed original cross sections presented in the present study, refer to the double differential (with respect to anglesΩ and the nuclear excitation energy ω), the single differential (with respect to the nuclear excitation energy ω), as well as to the cumulative (integrated) and the total cross sections. We employed an advantageous numerical approach published by our group recently, which provides state-by-state calculations of the relevant cross sections for all multipolarities emphasizing on the most important ones, i.e. those with J π 8 ± . For all isotopes studied, the differential and total cross sections as functions of the nuclear excitation energy ω, are dominated by contributions originating from the 1 − , 2 + xvii and 1 + multipolarities. We paid special attention on the dependence of the cross sections on the incoming neutrino energies (varying in the region ε ν 100 − 150 MeV), on the nuclear excitation energy of each isotope (ω 30 MeV) and on the other kinematical parameters. Due to the fact that, for all isotopes most of the low-lying transitions induced by the (anti)neutrino-nucleus interaction are the 2 + states, we studied them in more detail.The nuclear response of 64,66 Zn and 128,130 T e isotopes to supernova neutrino spectra, was studied by convoluting the original cross sections with well known supernova (anti)neutrino-energy distributions such as the two pa...