Measurement of atmospheric neutrino flux consistent with tau neutrino appearance

A search for the appearance of tau neutrinos from nu(mu) <--> nu(tau) oscillations in the atmospheric neutrinos has been performed using 1489.2 days of atmospheric neutrino data from the Super-Kamiokande-I experiment. A best fit tau neutrino appearance signal of 138+/-48(stat)-32(+15)(syst) events is obtained with an expectation of 78+/-26(syst). The hypothesis of no tau neutrino appearance is disfavored by 2.4 sigma.     

Inconsistencies in interpreting the atmospheric neutrino anomaly

We note a discrepancy between the value ofR expected on the basis of the muon neutrino angular distribution and the value actually observed. The energy independence ofR leads to a fine-tuning problem. This may be indicative of some unaccounted for new physics.     

Discovery of atmospheric neutrino oscillations**

Atmospheric neutrinos are produced by cosmic ray interactions in the atmosphere. The zenith‐angle and energy dependence of the muon‐ and electron‐ neutrino events are observed in atmospheric neutrino experiments. Through these studies neutrino oscillations were discovered. In this article, studies of atmospheric neutrinos in the Kamiokande and Super‐Kamiokande experiments are described.     

Prompt atmospheric neutrino production of W-bosons

It is shown that the recent CERN beam dump experiment implying direct neutrino production provides a straightforward way to detect W-bosons via ultrahigh energy cosmic rays hitting the atmosphere. This occurs because (1) at high energies, direct neutrinos will dominate over the standard π, K produced flux due to time dilation effects and (2) direct π-production produces a large fraction of $\text{ν}\text{?}{}_{\mathrm{e}}$.     

Search for neutrino radiative decay with a prototype Borexino detector

Results of background measurements with a prototype of the Borexino detector were used to obtain bounds on the lifetime of radiative neutrino decay ν_H→ν_L+γ. The new lower limit for the lifetime of pp and ⁷Be neutrinos is τ_c.m.(ν_H→ν_L+γ) /mν≥4.2×10³ s eV^?1(α)= 0). It is more than an order of magnitude stronger than the value obtained in previous experiments using nuclear reactors and accelerators.     

Search for neutrino radiation from collapsing stars with the Artyomovsk scintillation detector

The current status of an experiment designed to search for neutrino radiation from collapsing stars using the Artyomovsk Liquid Scintillation Detector is described. Observations were conducted from November 1977 to July 2012. The upper limit for the mean rate at which neutrino bursts occur in the Galaxy is found to be f _col < 0.0658 events per year at a 90% confidence level. In 35 years of observations, no supernovae were detected in the Galaxy.     

ORLANDO - Oak Ridge large neutrino detector

We discuss a proposal for construction of an Oak Ridge LArge Neutrino DetectOr (ORLANDO) to search for neutrino oscillations at the Spallation Neutron Source (SNS). A 4 MW SNS is proposed to be built at the Oak Ridge National Laboratory with the first stage to be operative around 2006. It will have two target stations, which makes it possible with a single detector to perform a neutrino oscillation search at two different distances. Initial plans for the placement of the detector and the discovery potential of such a detector are discussed.     

DANSSino: a pilot version of the DANSS neutrino detector

DANSSino is a reduced pilot version of a solid-state detector of reactor antineutrinos (to be created within the DANSS project and installed under the industrial 3 GW_th reactor of the Kalinin Nuclear Power Plant—KNPP). Numerous tests performed at a distance of 11 m from the reactor core demonstrate operability of the chosen design and reveal the main sources of the background. In spite of its small size (20 × 20 × 100 cm³), the pilot detector turned out to be quite sensitive to reactor antineutrinos, detecting about 70 IBD events per day with the signal-to-background ratio about unity.     

Study of atmospheric neutrino oscillations in ANTARES

The potential of the ANTARES 0.1 km² detector for the study of the atmospheric neutrino oscillations is discussed.     

Limits on neutrino emission from gamma-ray bursts with the 40 string IceCube detector

IceCube has become the first neutrino telescope with a sensitivity below the TeV neutrino flux predicted from gamma-ray bursts if gamma-ray bursts are responsible for the observed cosmic-ray flux above 10(18) eV. Two separate analyses using the half-complete IceCube detector, one a dedicated search for neutrinos from pγ interactions in the prompt phase of the gamma-ray burst fireball and the other a generic search for any neutrino emission from these sources over a wide range of energies and emission times, produced no evidence for neutrino emission, excluding prevailing models at 90% confidence.