Search results for " Neutrino"

Probing neutrino properties with charged scalar lepton decays

2002

Supersymmetry with bilinear R-parity violation provides a predictive framework for neutrino masses and mixings in agreement with current neutrino oscillation data. The model leads to striking signals at future colliders through the R-parity violating decays of the lightest supersymmetric particle. Here we study charged scalar lepton decays and demonstrate that if the scalar tau is the LSP (i) it will decay within the detector, despite the smallness of the neutrino masses, (ii) the relative ratio of branching ratios Br({tilde tau}_1 --> e sum nu_i)/ Br({tilde tau}_1 --> mu sum nu_i) is predicted from the measured solar neutrino angle, and (iii) scalar muon and scalar electron decays wi…

Probing neutrino non-standard interactions with atmospheric neutrino data

2001

We have reconsidered the atmospheric neutrino anomaly in light of the laetst data from Super-Kamiokande contained events and from Super-Kamiokande and MACRO up-going muons. We have reanalysed the proposed solution to the atmospheric neutrino anomaly in terms of non-standard neutrino-matter interactions (NSI) as well as the standard nu_mu -> nu_tau oscillations (OSC). Our statistical analysis shows that a pure NSI mechanism is now ruled out at 99%, while the standard nu_mu -> nu_tau OSC mechanism provides a quite remarkably good description of the anomaly. We therefore study an extended mechanism of neutrino propagation which combines both oscillation and non-standard neutrino-matter i…

Neutrino induced coherent pion production off nuclei and the partial conservation of the axial current

2009

15 pages, 7 figures, 1 table.-- PACS nrs.: 25.30.Pt; 12.15.-y; 13.15.+g.-- ArXiv pre-print available at: http://arxiv.org/abs/0903.5285

Bounds on the tau and muon neutrino vector and axial vector charge radius

2002

A Majorana neutrino is characterized by just one flavor diagonal electromagnetic form factor: the anapole moment, that in the static limit corresponds to the axial vector charge radius . Experimental information on this quantity is scarce, especially in the case of the tau neutrino. We present a comprehensive analysis of the available data on the single photon production process $e^+ e^- -> \nu \bar\nu \gamma$ off Z-resonance, and we discuss the constraints that these measurements can set on for the tau neutrino. We also derive limits for the Dirac case, when the presence of a vector charge radius is allowed. Finally, we comment on additional experimental data on $\nu_\mu$ scattering from t…

Effects of the axial isoscalar neutral current for solar neutrino detection

1992

Abstract An essential assumption in the analysis of all the large solar neutrino experiments sensitive to neutral currents has been that the axial transitions are purely isovector. The recent results on the spin structure of the proton suggest the presence of an axial isoscalar neutral-current interaction. This would modify the assumed transition strengths for the neutral-current detection of solar neutrinos. We demonstrate that in the long wavelength limit a deuterium target is insensitive to such a mechanism. Our results for the situation of the planned BOREX experiment show that the suggested isoscalar strength would increase the observed rate by 30–40%, depending on the transition.

Effects of non-standard neutrino-electron interactions on relic neutrino decoupling

2006

We consider the decoupling of neutrinos in the early Universe in presence of non-standard neutral current neutrino-electron interactions (NSI). We first discuss a semi-analytical approach to solve the relevant kinetic equations and then present the results of fully numerical and momentum-dependent calculations, including flavor neutrino oscillations. We present our results in terms of both the effective number of neutrino species (N_eff) and the impact on the abundance of He-4 produced during Big Bang Nucleosynthesis. We find that, for NSI parameters within the ranges allowed by present laboratory data, non-standard neutrino-electron interactions do not essentially modify the density of rel…

New results on a search for a 33.9 MeV/c2 neutral particle from π+ decay in the NOMAD experiment

2002

We report on a direct search in NOMAD for a new 33.9 MeV/c^2 neutral particle (X) produced in pion decay in flight, pi-->mu_X followed by the decay X -->nu e^+e^-. Both decays are postulated to occur to explain the time anomaly observed by the KARMEN experiment. From the analysis of the data collected during the 1996?1998 runs with 4.1×10^19 protons on target, a single candidate event consistent with background expectations was found. The search is sensitive to a pion branching ratio BR(pi-->muX >3.7×10^-15, significantly smaller than previous experimental limits.

Neutrino mixing and future accelerator neutrino experiments

1992

Status of a hybrid three-neutrino interpretation of neutrino data

2001

We reanalyze the non-standard interaction (NSI) solutions to the solar neutrino problem in the light of the latest solar, atmospheric and reactor neutrino data. We show that such solutions, although preferred by the solar data and consistent with the oscillation description of the atmospheric neutrino data, are ruled out by the first results of the KamLAND reactor experiment, at more than 3_sigma.

Solving the solar neutrino puzzle with KamLAND and solar data

2001

We study what will be learnt about the solar neutrino puzzle and solar neutrino oscillations once the data from the KamLAND reactor neutrino experiment (soon to become available) are combined with those from the current solar neutrino experiments. We find that, in agreement with previous estimates, if the solution to the solar neutrino puzzle falls on the LMA region, KamLAND should be able to ``pin-point'' the right solution with unprecedented accuracy after a few years of data taking. Furthermore, the light side ($\theta\pi/4$) at the 95% confidence level (CL) for most of the LMA region allowed by the current data at the 99% CL, while the addition of the KamLAND data need not improve our a…