Search results for "mixing"
showing 10 items of 795 documents
Atmospheric neutrino oscillations and new physics
2004
We study the robustness of the determination of the neutrino masses and mixing from the analysis of atmospheric and K2K data under the presence of different forms of phenomenologically allowed new physics in the nu_mu--nu_tau sector. We focus on vector and tensor-like new physics interactions which allow us to treat, in a model independent way, effects due to the violation of the equivalence principle, violations of the Lorentz invariance both CPT conserving and CPT violating, non-universal couplings to a torsion field and non-standard neutrino interactions with matter. We perform a global analysis of the full atmospheric data from SKI together with long baseline K2K data in the presence of…
Resolving the octant of theta(23) with T2K and NOvA
2013
Preliminary results of MINOS experiment indicate that theta(23) is not maximal. Global fits to world neutrino data suggest two nearly degenerate solutions for theta(23): one in the lower octant (LO: theta(23) 45 degrees). v(mu) -> v(e) oscillations in superbeam experiments are sensitive to the octant and are capable of resolving this degeneracy. We study the prospects of this resolution by the current T2K and upcoming NOvA experiments. Because of the hierarchy-delta(CP) degeneracy and the octant delta(CP) degeneracy, the impact of hierarchy on octant resolution has to be taken into account. As in the case of hierarchy determination, there exist favorable (unfavorable) values of delta(CP) fo…
Exact relativistic beta decay endpoint spectrum
2007
5 pages, 3 figures.-- PACS nrs.: 14.60.Pq; 13.30.-a; 23.40.-s; 23.40.Bw.-- ISI Article Identifier: 000250620900070.-- ArXiv pre-print available at: http://arxiv.org/abs/0706.0897
Supernova bounds on resonant active-sterile neutrino conversions
1997
We discuss the effects of resonant $\nu_e \to \nu_s$ and $\bar{\nu}_e \to \bar{\nu}_s$ ($\nu_s$ is a sterile neutrino) conversions in the dense medium of a supernova. In particular, we assume the sterile neutrino $\nu_s$ to be in the hot dark matter few eV mass range. The implications of such a scenario for the supernova shock re-heating, the detected $\bar\nu_e$ signal from SN1987A and for the r-process nucleosynthesis hypothesis are analysed in some detail. The resulting constraints on mixing and mass difference for the $\nu_e-\nu_s$ system are derived. There is also an allowed region in the neutrino parameter space for which the r-process nucleosynthesis can be enhanced.
Constraining the invisible neutrino decay with KM3NeT-ORCA
2019
Several theories of particle physics beyond the Standard Model consider that neutrinos can decay. In this work we assume that the standard mechanism of neutrino oscillations is altered by the decay of the heaviest neutrino mass state into a sterile neutrino and, depending on the model, a scalar or a Majoron. We study the sensitivity of the forthcoming KM3NeT-ORCA experiment to this scenario and find that it could improve the current bounds coming from oscillation experiments, where three-neutrino oscillations have been considered, by roughly two orders of magnitude. We also study how the presence of this neutrino decay can affect the determination of the atmospheric oscillation parameters $…
Search for heavy neutrinos mixing with tau neutrinos
2001
We report on a search for heavy neutrinos ($\nus$) produced in the decay $D_s\to \tau \nus$ at the SPS proton target followed by the decay $\nudecay$ in the NOMAD detector. Both decays are expected to occur if $\nus$ is a component of $\nu_{\tau}$.\ From the analysis of the data collected during the 1996-1998 runs with $4.1\times10^{19}$ protons on target, a single candidate event consistent with background expectations was found. This allows to derive an upper limit on the mixing strength between the heavy neutrino and the tau neutrino in the $\nus$ mass range from 10 to 190 $\rm MeV$. Windows between the SN1987a and Big Bang Nucleosynthesis lower limits and our result are still open for f…
Do T asymmetries for neutrino oscillations in uniform matter have a CP-even component?
2019
Observables of neutrino oscillations in matter have, in general, contributions from the effective matter potential. It contaminates the CP violation asymmetry adding a fake effect that has been recently disentangled from the genuine one by their different behavior under T and CPT. Is the genuine T-odd CPT-invariant component of the CP asymmetry coincident with the T asymmetry? Contrary to CP, matter effects in uniform matter cannot induce by themselves a non-vanishing T asymmetry; however, the question of the title remained open. We demonstrate that, in the presence of genuine CP violation, there is a new non-vanishing CP-even, and so CPT-odd, component in the T asymmetry in matter, which i…
Flavored CP asymmetries for type II seesaw leptogenesis
2013
A novel contribution to the leptonic CP asymmetries in type II seesaw leptogenesis scenarios is obtained for the cases in which flavor effects are relevant for the dynamics of leptogenesis. In the so-called flavored leptogenesis regime, the interference between the tree-level amplitude of the scalar triplet decaying into two leptons and the one-loop wave function correction with leptons in the loop, leads to a new nonvanishing CP asymmetry contribution. The latter conserves total lepton number but violates lepton flavor. Cases in which this novel contribution may be dominant in the generation of the baryon asymmetry are briefly discussed.
Isospin-symmetry breaking in masses of ≃ Nuclei
2018
Effects of the isospin-symmetry breaking (ISB) beyond mean-field Coulomb terms are systematically studied in nuclear masses near the N=Z line. The Coulomb exchange contributions are calculated exactly. We use extended Skyrme energy density functionals (EDFs) with proton–neutron-mixed densities, to which we add new terms breaking the isospin symmetry. Two parameters associated with the new terms are determined by fitting mirror and triplet displacement energies (MDEs and TDEs) of isospin multiplets. The new EDFs reproduce MDEs for the T=12 doublets and T=1 triplets, and TDEs for the T=1 triplets. Relative strengths of the obtained isospin-symmetry-breaking terms are not consistent with the d…
A collision timing monitor for SuperKEKB
2017
Abstract The analysis of beamstrahlung radiation, emitted from a beam of charged particles due to the electromagnetic interaction with a second beam of charged particles, provides a diagnostic tool that can be used to monitor beam–beam collisions in a e + e − storage ring. In this paper we show that the beamstrahlung time profile is related to the timing of the collisions and the length of the beams, and how its measurement can be used to monitor and optimize collisions at the interaction point of the SuperKEKB collider. The method has a unique passive monitor capability, since it allows to monitor the timing of the collision without disturbing (scanning) the beam–beam timing, which needs t…