Search results for "NEUTRINO"
showing 10 items of 1752 documents
Neutrinoless ββ decays to excited 0+ states and the Majorana-neutrino mass
2016
The nuclear matrix elements (NMEs) corresponding to the neutrinoless double-β (0νββ) decays to excited 0+ states of major experimental interest are calculated. All these decay transitions are electron emitting (0νβ−β− decays) and take place in the mass A = 76,82,96,100,110,116,124,130,136 nuclei. This work is an extension of our previous work [Phys. Rev. C 91, 024613 (2015)], where 0νββ decays to the ground states of the same nuclei were treated. We calculate the NMEs for transitions mediated by both the light (l-NMEs) and the heavy (h-NMEs) Majorana neutrinos. A higher-QRPA (quasiparticle random-phase approximation) framework, the multiple-commutator model, is adopted for the calculations,…
First-forbidden transitions in the reactor anomaly
2018
We study the dominant forbidden transitions in the antineutrino spectra of the fission actinides from 4 MeV onward using the nuclear shell model. Through explicit calculation of the shape factor, taking into account Coulomb corrections, we show the expected changes on cumulative electron and antineutrino spectra. Compared to the usual allowed approximation this results in a minor decrease of electron spectra from 4 MeV and onward, whereas an increase of several percent is observed in antineutrino spectra. We show that, despite their limited number, forbidden transitions dominate the spectral flux for most of the experimentally accessible range. Based on the shell model calculations we attem…
Nuclear matrix elements for 0νββ decays with light or heavy Majorana-neutrino exchange
2015
We compute the nuclear matrix elements (NMEs) corresponding to the neutrinoless double beta (0νββ) decays of nuclei which attract current experimental interest. We concentrate on ground-state-to-ground-state decay transitions mediated by light (l-NMEs) or heavy (h-NMEs) Majorana neutrinos. The computations are done in realistic single-particle model spaces using the proton-neutron quasiparticle random-phase approximation (pnQRPA) with two-nucleon interactions based on the Bonn one-boson-exchange G matrix. Both the l-NMEs and the h-NMEs include the appropriate short-range correlations, nucleon form factors, and higher-order nucleonic weak currents. In addition, both types of NMEs are correct…
Photon emission in neutral current interactions with nucleons and nuclei
2013
We report on our study of photon emission induced by Enu ~ 1 GeV (anti)neutrino neutral current interactions with nucleons and nuclei. This process is an important background for nu_e appearance oscillation experiments. At the relevant energies, the reaction is dominated by the excitation of the Delta (1232) resonance but there are also non-resonant contributions that, close to threshold, are fully determined by the effective chiral Lagrangian of strong interactions. We have obtained differential and integrated cross section for the (anti)neutrino-nucleon scattering and compare them with previous results. Furthermore, we have extended the model to nuclear targets taking into account Fermi m…
Neutrinoless ββ nuclear matrix elements using isovector spin-dipole Jπ = 2− data
2018
Ground-state-to-ground-state neutrinoless double-beta (0νββ) decays in nuclei of current experimental interest are revisited. In order to improve the reliability of the nuclear matrix element (NME) calculations for the light Majorana-neutrino mode, the NMEs are calculated by exploiting the newly available data on isovector spin-dipole (IVSD) Jπ=2− giant resonances. In order to correctly describe the IVSD up to and beyond the giant-resonance region, the present computations are performed in extended no-core single-particle model spaces using the spherical version of the proton-neutron quasiparticle random-phase approximation (pnQRPA) with two-nucleon interactions based on the Bonn one-boson-…
Neutral-current supernova-neutrino cross sections for 204,206,208Pb calculated by Skyrme quasiparticle random-phase approximation
2019
The present work constitutes a detailed study of neutral-current (NC) supernova-neutrino scattering off the stable even-even lead isotopes 204,206,208Pb. This is a continuation of our previous work [Almosly et al., Phys. Rev. C. 94, 044614 (2016)] where we investigated charged-current processes on the same nuclei. As in the previous work, we have adopted the quasiparticle random-phase approximation (QRPA) as the theory framework and use three different Skyrme interactions to build the involved nuclear wave functions. We test the Skyrme forces by computing the location of the lowest-order isovector spin-multipole giant resonances and comparing with earlier calculations. We have computed the …
First Muon-Neutrino Disappearance Study with an Off-Axis Beam
2012
We report a measurement of muon-neutrino disappearance in the T2K experiment. The 295-km muon-neutrino beam from Tokai to Kamioka is the first implementation of the off-axis technique in a long-baseline neutrino oscillation experiment. With data corresponding to 1.43 × 10(20) protons on target, we observe 31 fully-contained single μ-like ring events in Super-Kamiokande, compared with an expectation of 104 ± 14(syst) events without neutrino oscillations. The best-fit point for two-flavor νμ → ντ oscillations is sin 2(2θ(23)) = 0.98 and |Δm(2)(32)| = 2.65 × 10(−3) eV2. The boundary of the 90% confidence region includes the points (sin2 (2θ(23)), |Δm(2)(32)|) = (1.0, 3.1 × 10(−3) eV2), (0.84, …
Searching for Physics Beyond the Standard Model in an Off-Axis DUNE Near Detector
2021
Next generation neutrino oscillation experiments like DUNE and T2HK are multi-purpose observatories, with a rich physics program beyond oscillation measurements. A special role is played by their near detector facilities, which are particularly well-suited to search for weakly coupled dark sector particles produced in the primary target. In this paper, we demonstrate this by estimating the sensitivity of the DUNE near detectors to the scattering of sub-GeV DM particles and to the decay of sub-GeV sterile neutrinos ("heavy neutral leptons"). We discuss in particular the importance of the DUNE-PRISM design, which allows some of the near detectors to be moved away from the beam axis. At such o…
Four-neutrino oscillations at SNO
2000
We discuss the potential of SNO to constraint the four-neutrino mixing schemes favoured by the results of all neutrino oscillations experiments. These schemes allow simultaneous transitions of solar $\nu_e's$ into active $\nu_\mu$'s, $\nu_\tau$'s and sterile $\nu_s$ controlled by the additional parameter $\cos^2(\vartheta_{23}) \cos^2(\vartheta_{24})$ and they contain as limiting cases the pure $\nu_e$-active and $\nu_e$-sterile neutrino oscillations. We first obtain the solutions allowed by the existing data in the framework of the BP00 standard solar model and quantify the corresponding predictions for the CC and the NC/CC event ratios at SNO for the different allowed regions as a functio…
Seasonal dependence in the solar neutrino flux
1999
MSW solutions of the solar neutrino problem predict a seasonal dependence of the zenith angle distribution of the event rates, due to the non-zero latitude at the Super-Kamiokande site. We calculate this seasonal dependence and compare it with the expectations in the no-oscillation case as well as just-so scenario, in the light of the latest Super-Kamiokande 708-day data. The seasonal dependence can be sizeable in the large mixing angle MSW solution and would be correlated with the day-night effect. This may be used to discriminate between MSW and just-so scenarios and should be taken into account in refined fits of the data.