Simulated Neutrino Signals of Low and Intermediate Energy Neutrinos on Cd Detectors

Neutrino-nucleus reactions cross sections, obtained for neutrino energies in the range εν ≤ 100–120 MeV (low- and intermediate-energy range), which refer to promising neutrino detection targets of current terrestrial neutrino experiments, are presented and discussed. At first, we evaluated original cross sections for elastic scattering of neutrinos produced from various astrophysical and laboratory neutrino sources with the most abundant Cd isotopes 112Cd, 114Cd, and 116Cd. These isotopes constitute the main material of the COBRA detector aiming to search for neutrinoless double beta decay events and neutrino-nucleus scattering events at the Gran Sasso laboratory (LNGS). The coherent ν-nucleus reaction channel addressed with emphasis here, dominates the neutral current ν-nucleus scattering, events of which have only recently been observed for a first time in the COHERENT experiment at Oak Ridge. Subsequently, simulated ν-signals expected to be recorded at Cd detectors are derived through the application of modern simulation techniques and employment of reliable neutrino distributions of astrophysical ν-sources (as the solar, supernova, and Earth neutrinos), as well as laboratory neutrinos (like the reactor neutrinos, the neutrinos produced from pion-muon decay at rest and the β-beam neutrinos produced from the acceleration of radioactive isotopes at storage rings as e.g., at CERN).PACS numbers: 26.50.+x, 25.30.Pt, 97.60.Bw, 25.30.-c, 23.40.Bw, 21.60.J

Convoluted ν-Signals on 114Cd Isotope from Astrophysical and Laboratory Neutrino Sources

At first, we evaluate scattering cross sections of low, and intermediate-energy neutrinos scattered off the 114 Cd isotope, the most abundant Cd isotope present also in the COBRA detector (CdTe and CdZnTe materials) which aims to search for double beta decay events and neutrino observations at Gran Sasso laboratory (LNGS). The coherent ν-nucleus channel addressed here is the dominant reaction channel of the neutral current ν-nucleus scattering. Our ν-nucleus cross sections (calculated with a refinement of the quasiparticle random-phase approximation, QRPA) refer to the gs→gs transitions for ν-energies εν≤100 MeV. Subsequently, simulated ν-signals on 114 Cd isotope are derived. Towards this purpose, the required folded cross section comes out of simulation techniques by employing several low, and intermediate-energy neutrino distributions of the astrophysical ν-sources, like the solar, supernova, and Earth neutrinos, as well as the laboratory neutrinos, the reactor neutrinos, the pion-muon stopped neutrinos, and the β-beam neutrinos

Cd Isotope from Astrophysical and Laboratory Neutrino Sources

At first, we evaluate scattering cross sections of low, and intermediate-energy neutrinos scattered off the 114 Cd isotope, the most abundant Cd isotope present also in the COBRA detector (CdTe and CdZnTe materials) which aims to search for double beta decay events and neutrino observations at Gran Sasso laboratory (LNGS). The coherent ]-nucleus channel addressed here is the dominant reaction channel of the neutral current ]-nucleus scattering. Our ]-nucleus cross sections (calculated with a refinement of the quasiparticle random-phase approximation, QRPA) refer to the → transitions for ]-energies ] ≤ 100 MeV. Subsequently, simulated ]-signals on 114 Cd isotope are derived. Towards this purpose, the required folded cross section comes out of simulation techniques by employing several low, and intermediate-energy neutrino distributions of the astrophysical ]-sources, like the solar, supernova, and Earth neutrinos, as well as the laboratory neutrinos, the reactor neutrinos, the pion-muon stopped neutrinos, and the -beam neutrinos

Study of astrophysical neutrinos with simulation techniques and nuclear structure calculations

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 spectra of various nuclear detectors used recently in terrestrial experiments searching for events of rare process. We concentrated on the systematic studies of the (anti)neutrino-64,66Zn , 128,130Te reactions. The nuclei Te and Zn, are contents of the CdZnTe and CdTe semi-detectors, 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)neutrino-nucleus reaction cross sections are evaluated within the context of the quasi-particle random phase approximation (QRPA). The detailed original cross sections presented in the present study, refer to the double differential, the single differential, the cumulative 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 Jπ ≤ 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+ and 1+ multipolarities. We paid special attention on the dependence of the cross sections on the incoming neutrino energies, on the nuclear excitation energy of each isotope and on the other kinematical parameters. The nuclear response of 64,66Zn and 128,130Te isotopes to supernova neutrino energy spectra, was studied by convoluting the original cross sections with well known supernova (anti)neutrino energy distributions such as the Fermi-Dirac and Power-Law. We also explored the interpretation of the supernova neutrino signals created on the aforementioned nuclear detectors by using the low-energy beta-beam spectra of boosted β-radioactive nuclei. Work obtained by using the MERLIN optimization package. This response, reflects the effectiveness of the COBRA semi-contactors as supernova neutrino detectors. The results of the original (anti)neutrino-nucleus cross sections are also useful for modelling the neutrino-nucleosynthesis in the interior of massive stars.Στην παρούσα διδακτορική διατριβή, μελετώνται αστροφυσικά νετρίνα χαμηλών και ενδιαμέσων ενεργειών, με λεπτομερειακούς υπολογισμούς πυρηνικής δομής και χρήση σύγχρονων τεχνικών προσομοίωσης. Ένας από τους κύριους στόχους, ήταν η διερεύνηση της πυρηνικής απόκρισης στα φάσματα των σούπερνόβα νετρίνων διαφόρων ισοτόπων, τα οποία χρησιμοποιούνται σε πρόσφατα πειράματα έρευνας διαδικασιών με σπάνια γεγονότα. Επικεντρώσαμε την προσοχή μας στη συστηματική μελέτη των αντιδράσεων (αντι)νετρίνων με τα ισότοπα 64,66Zn και 128,130Te. Οι πυρήνες Zn και Te, είναι συστατικά των ημιαγωγών CdZnTe και CdTe, οι οποίοι έχουν επιλεγεί για ανιχνευτές στο πείραμα COBRA στο Gran Sasso. Από την άποψη της πυρηνικής δομής, οι πρωτογενείς υπολογισμοί ενεργών διατομών (αντι)νετρίνου-πυρήνα, έχουν γίνει χρησιμοποιώντας την προσέγγιση τυχαίας φάσης με ημισωμάτια (QRPA). Τα αποτελέσματα των ενεργών διατομών που παρουσιάζονται, αναφέρονται στη διπλή διαφορική, στην απλή διαφορική, στη σωρρευτική (αθροιστική) και στην ολική ενεργό διατομή. Για τους υπολογισμούς των πυρηνικών στοιχείων πίνακα, χρησιμοποιήσαμε την πλενονεκτική μέθοδο που κατασκευάστηκε πρόσφατα, κατάλληλη για υπολογισμούς κατάσταση-προς-κατάσταση όλων των αναγκαίων ενεργών διατομών. Εστιάσαμε σε ξεχωριστούς υπολογισμούς της συνεισφοράς όλων των πολυπολικών καταστάσεων (με Jπ ≤ 8±). Για όλα τα ισότοπα που μελετήσαμε, οι κυρίαρχες πολυπολικές καταστάσεις είναι οι 1-, 2+ και 1+ , τόσο στις διαφορικές όσο και στις ολικές ενεργές διατομές. Μελετήσαμε ιδιαίτερα την εξάρτηση των ενεργών διατομών από την ενέργεια του εισερχομένου νετρίνου, την ενέργεια διέγερσης του πυρήνα-ανιχνευτή , καθώς και από άλλες κινηματικές παραμέτρους. Η απόκριση των ισοτόπων 64,66Zn και 128,130Te στα φάσματα των υπερκαινοφανών νετρίνων, μελετήθηκε υπολογίζοντας την συνέλιξη των πρωτογενών ενεργών διατομών με κατανομές υπερκαινοφανών (αντι)νετρίνων, όπως οι Fermi-Dirac και Power-Law. Διερευνήθηκε επίσης, η ερμηνεία του σήματος υπερκαινοφανών νετρίνων που παράγεται στον πυρηνικό ανιχνευτή, χρησιμοποιώντας φάσματα χαμηλής ενέργειας νετρίνων β-δέσμης, προερχόμενα από β-ραδιενεργούς πυρήνες επιταχυνομένους σε αποθηκευτικούς δακτυλίους. Η διαδικασία προσαρμογής υλοποιήθηκε χρησιμοποιώντας το λογισμικό MERLIN. Η ανωτέρω απόκριση, αντανακλά την αποδοτικότητα των πυρηνικών στόχων σαν ανιχνευτές (αντι)νετρίνων. Τα αποτελέσματα των ενεργών διατομών της παρούσας έρευνας, μπορούν να χρησιμοποιηθούν και σε κώδικες περιγραφής της πυρηνοσύνθεσης των μαζικών αστέρων

Simulated neutrino signals of low and intermediate energy neutrinos on Cd detectors

Neutrino-nucleus reactions cross sections, obtained for neutrino energies in the range $\varepsilon_{\nu}\leq 100-120$ MeV (low- and intermediate-energy range), which refer to promising neutrino detection targets of current terrestrial neutrino experiments, are presented and discussed. At first, we evaluated original cross sections for elastic scattering of neutrinos produced from various astrophysical and laboratory neutrino sources with the most abundant Cd isotopes $^{112}$Cd, $^{114}$Cd and $^{116}$Cd. These isotopes constitute the main material of the COBRA detector aiming to search for neutrinoless double beta decay events and neutrino-nucleus scattering events at the Gran Sasso laboratory (LNGS). The coherent $\nu$-nucleus reaction channel addressed with emphasis here, dominates the neutral current $\nu$-nucleus scattering, events of which have only recently been observed for a first time in the COHERENT experiment at Oak Ridge. Subsequently, simulated $\nu$-signals expected to be recorded at Cd detectors are derived through the application of modern simulation techniques and employment of reliable neutrino distributions of astrophysical $\nu$-sources (as the solar, supernova and Earth neutrinos), as well as laboratory neutrinos (like the reactor neutrinos, the neutrinos produced from pion-muon decay at rest and the $\beta$-beam neutrinos produced from the acceleration of radioactive isotopes at storage rings as e.g. at CERN)

Neutral-current neutrino-nucleus reactions and their impact to supernova physics

We study neutral-current neutrino-nucleus reactions in nuclei that are relevant for supernova (SN) simulations and for terrestrial experiments aiming at neutrino astrophysics as well as ν-nucleus scattering cross sections measurements. Such studies allow us to improve estimates of nuclear responses to low energy neutrinos in light of the operation of nuclear v-detectors with very-low threshold and very high sensitivity. The adopted ν-energy range is extended to rather high energies (up to 100 MeV) so as to consider allowed and forbidden multipole contributions to cross sections. Both contributions are calculated within the quasi-particle random phase approximation by using realistic two-body forces (Bonn CD potential) for the residual interaction of the nuclear Hamiltonian. As a special application the 56Fe isotope is chosen due to its significant role in SN physics and ν-detection. © Published under licence by IOP Publishing Ltd.SCOPUS: cp.jinfo:eu-repo/semantics/publishe