Search results for " Neutrino"
showing 10 items of 727 documents
Type-II Supernovae and Neutrino Magnetic Moment
1998
The present solar and atmospheric neutrino data together with the LSND results and the presence of hot dark matter (HDM) suggest the existence of a sterile neutrino at the eV scale. We have reanalysed the effect of resonant {\sl sterile} neutrino conversions induced by neutrino magnetic moments in a type-II supernova. We analyse the implications of $\nu_e-\nu_s$ and $\bar{\nu}_e-\bar{\nu}_s$ ($\nu_s$ denotes sterile neutrino) conversions for the supernova shock re-heating, the detected $\bar\nu_e$ signal from SN1987A and the $r$-process nucleosynthesis hypothesis. Using reasonable magnetic field profiles we determine the sensitivity of these three arguments to the relevant neutrino paramete…
Relic neutrinos, thermal axions, and cosmology in early 2014
2014
We present up to date cosmological bounds on the sum of active neutrino masses as well as on extended cosmological scenarios with additional thermal relics, as thermal axions or sterile neutrino species. Our analyses consider all the current available cosmological data in the beginning of year 2014, including the very recent and most precise Baryon Acoustic Oscillation (BAO) measurements from the Baryon Oscillation Spectroscopic Survey. In the minimal three active neutrino scenario, we find Sum m_nu < 0.22 eV at 95% CL from the combination of CMB, BAO and Hubble Space Telescope measurements of the Hubble constant. A non zero value for the sum of the three active neutrino masses of about …
Cosmological limits on neutrino unknowns versus low redshift priors
2015
Recent Cosmic Microwave Background (CMB) temperature and polarization anisotropy measurements from the Planck mission have significantly improved previous constraints on the neutrino masses as well as the bounds on extended models with massless or massive sterile neutrino states. However, due to parameter degeneracies, additional low redshift priors are mandatory in order to sharpen the CMB neutrino bounds. We explore here the role of different priors on low redshift quantities, such as the Hubble constant, the cluster mass bias, and the reionization optical depth $\tau$. Concerning current priors on the Hubble constant and the cluster mass bias, the bounds on the neutrino parameters may di…
Effects of degenerate sterile neutrinos on the supernova neutrino flux
2004
We consider the possibility that there exist sterile neutrinos which are closely degenerate in mass with the active neutrinos and mixed with them. We investigate the effects of this kind of active-sterile neutrino mixing on the composition of supernova neutrino flux at the Earth. If an adiabatic MSW-transition between active and sterile neutrinos takes place, it could dramatically diminish the electron neutrino flux.
Helicitogenesis: WIMPy baryogenesis with sterile neutrinos and other realizations
2014
We propose a mechanism for baryogenesis from particle decays or annihilations that can work at the TeV scale. Some heavy particles annihilate or decay into a heavy sterile neutrino N (with M > 0.5 TeV) and a "light" one ��(with m << 100 GeV), generating an asymmetry among the two helicity degrees of freedom of ��. This asymmetry is partially transferred to Standard Model leptons via fast Yukawa interactions and reprocessed into a baryon asymmetry by the electroweak sphalerons. We illustrate this mechanism in a WIMPy baryogenesis model where the helicity asymmetry is generated in the annihilation of dark matter. This model connects the baryon asymmetry, dark matter, and neutrino mas…
Impact of New Physics on CP-Asymmetries at Long Baselines
2018
We study the impact of new physics on CP-asymmetries using different oscillation channels at long baseline experiments.
Probing light sterile neutrino signatures at reactor and Spallation Neutron Source neutrino experiments
2017
We investigate the impact of a fourth sterile neutrino at reactor and Spallation Neutron Source neutrino detectors. Specifically, we explore the discovery potential of the TEXONO and COHERENT experiments to subleading sterile neutrino effects through the measurement of the coherent elastic neutrino-nucleus scattering event rate. Our dedicated $\chi^2$-sensitivity analysis employs realistic nuclear structure calculations adequate for high purity sub-keV threshold Germanium detectors.
Experimental searches on sterile neutrinos
2015
While neutrino oscillations among the three active neutrino flavors are by now well established, several anomalies observed at relatively short baselines in oscillation experiments hint towards the existence of one or more additional sterile neutrino flavors. As a consequence, several experiments are in preparation that are dedicated to test the sterile neutrino hypothesis. The present contribution gives an overview of the on-going experimental efforts, highlighting the two projects that are foreseen to start in 2015: SOX deploying a radioactive neutrino source at short distance from the BOREXINO detector at LNGS, and STEREO searching for sterile neutrino oscillations at short distance from…
Atmospheric neutrino observations and flavor changing interactions
1999
Flavor changing (FC) neutrino-matter interactions can account for the zenith-angle dependent deficit of atmospheric neutrinos observed in the SuperKamiokande experiment, without directly invoking neither neutrino mass, nor mixing. We find that FC $\nu_\mu$-matter interactions provide a good fit to the observed zenith angle distributions, comparable in quality to the neutrino oscillation hypothesis. The required FC interactions arise naturally in many attractive extensions of the Standard Model.
Problems in neutrino physics
1990
The three “known” neutrinos νe νµ and ντ, as well as their postulated heavy companions, have been the subject of intense experimental and theoretical research over the last decade. And yet, all the basic questions that we raised when the first, controversial, results on the mass of electron neutrino from triton beta decay were announced and when the new generation of experiments on lepton family changing processes started, remain essentially unanswered, in spite of the impressive effort that went into neutrino research [1]. So we may just repeat some of these questions and then see what we know about them and what remains to be done.