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.     

The search for different neutrino flavors from collapsing stars using the LVD detector

The main goal of the Large Volume Detector (LVD) is to search for neutrino burst from gravitational stellar collapses in our Galaxy. The apparatus is shown to be able to register stellar collapse even if there is none of the antineutrino emission specific to the standard scenario. The data from more than nine years of detector operation have been processed, and no candidate events for neutrino bursts have been detected. This implies the existence of an experimental limit to the galactic stellar collapse rate in those cases where collapse is not accompanied by electron antineutrino emission: less than one event per 4.1 yr at the 90% confidence level.     

Search for low-energy neutrino radiation accompanying gamma-ray bursts on the Baksan subterranean scintillation telescope

An analysis aimed at finding possible neutrino radiation accompanying gamma-ray bursts in a 24-h period about them is performed on the basis of the data in the 4B BATSE Gamma-Ray Burst Catalog and data from the Baksan scintillation telescope according to a program for finding neutrinos from collapsing stars. Values significantly exceeding the background are not discovered. A lower bound for the distance to the source is established under the assumption that the anticipated radiation has characteristics similar to the characteristics of collapse neutrinos. It attests to the cosmological origin of gamma-ray bursts with a high degree of probability. Zh. éksp. Teor. Fiz. 114, 1921–1929 (December 1998)     

Search for Neutrino Bursts from Collapsing Stars by Means of the LVD and BUST Detectors

A long-term and stable operation of the LVD and BUST detectors in searches for neutrino bursts from gravitational star collapses is demonstrated, and a random origin of background pulses in the detectors is confirmed thereby. The experimental results obtained by means of the LSD and BUST detectors on February 23, 1987, are considered in detail. The probability for the possible backgroundmimicked coincidences of clusters of pulses recorded in the LSD detector at 2 : 52 UT with a group of correlations of pulses within 1 s between LSD and BUST in the interval from 1 : 45 to 3 : 45 UT is estimated. Also, coincidences of the background pulses in the LVD and BUST detectors over the period of about eight years are analyzed. The results obtained in this way give sufficient grounds to conclude that the cluster of pulses recorded by the LSD detector on February 23, 1987, at 2 : 52 UT and the coincidences of individual pulses in the LSD and BUST detectors are events associated with the gravitational collapse of SN 1987A.     

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.     

The search for neutrino bursts from supernovae with Baksan underground scintillation telescope

The current status of the experiment on recording neutrino bursts from core collapse stars is presented. The actual observational time is 29.76 years. An upper bound of the mean frequency of core collapse supernovae in our Galaxy is f_col < 0.077 year–1 (90% CL).     

Search for neutrino emission from supernovae using the Large Volume Detector

The basic task of the Large Volume Detector LVD situated at the underground Gran Sasso National Laboratory (Italy) is the search for neutrino bursts from gravitational stellar collapses in our Galaxy. At present, the algorithm for determining neutrino bursts has been developed. It is based on the identification of event clusters in fixed time intervals, special attention is paid not only to the inverse β decay reaction which has a characteristic signature, but also to the neutrino-iron interaction. The data for of 3.5 years of LVD operation have been processed. No candidates for neutrino bursts are found.     

Prospects of the search for neutrino bursts from supernovae with Baksan large volume scintillation detector

Observing a high-statistics neutrino signal from the supernova explosions in the Galaxy is a major goal of low-energy neutrino astronomy. The prospects for detecting all flavors of neutrinos and antineutrinos from the core-collapse supernova (ccSN) in operating and forthcoming large liquid scintillation detectors (LLSD) are widely discussed now. One of proposed LLSD is Baksan Large Volume Scintillation Detector (BLVSD). This detector will be installed at the Baksan Neutrino Observatory (BNO) of the Institute for Nuclear Research, Russian Academy of Sciences, at a depth of 4800 m.w.e. Low-energy neutrino astronomy is one of the main lines of research of the BLVSD.     

The search for neutrino bursts from core collapse Supernovae at the Baksan Underground Scintillation Telescope

The current status of the experiment on recording neutrino bursts from core collapse stars is presented. The actual observational time T (from June 30, 1980 until December 31, 2009) is 25.58 years. An upper bound of the mean frequency of gravitational collapse in our Galaxy f _col < 0.090 year^?1 at a 90% confidence level. The results of studying single events at the facility in the case of muon inelastic interaction of cosmic rays with the matter of the detector are presented.     

Gravitational waves and neutrino emission from the merger of binary neutron stars

Numerical simulations for the merger of binary neutron stars are performed in full general relativity incorporating a finite-temperature (Shen's) equation of state (EOS) and neutrino cooling for the first time. It is found that for this stiff EOS, a hypermassive neutron star (HMNS) with a long lifetime (?10 ms) is the outcome for the total mass ?3.0M(⊙). It is shown that the typical total neutrino luminosity of the HMNS is ～3-8×10(53) erg/s and the effective amplitude of gravitational waves from the HMNS is 4-6×10(-22) at f=2.1-2.5 kHz for a source distance of 100 Mpc. We also present the neutrino luminosity curve when a black hole is formed for the first time.     

Searching for neutrino bursts in the galaxy: 36 years of exposure

The Baksan Underground Scintillation Telescope has operated within the program of searching for neutrino bursts since the mid-1980s. We present the current status of the experiment and some results related to the investigation of background events and the stability of facility operation. Over the period from June 30, 1980, to December 31, 2016, the pure observation time was 31.27 years. No neutrino burst candidate event from the explosion of a core-collapse supernova in the Galaxy was recorded in this time. This sets an upper bound of 0.074 yr^–1 on the mean frequency of gravitational stellar collapses in the Galaxy at a 90% confidence level.     

Determination of absolute neutrino masses from bursts of Z bosons in cosmic rays

Ultrahigh energy neutrinos (UHEnu) scatter on relic neutrinos (Rnu) producing Z bosons, which can decay hadronically producing protons (Z burst). We compare the predicted proton spectrum with the observed ultrahigh energy cosmic ray (UHECR) spectrum and determine the mass of the heaviest Rnu via a maximum likelihood analysis. Our prediction depends on the origin of the powerlike part of the UHECR spectrum: m(nu) = 2.75(+1.28)(-0.97) eV for Galactic halo and 0.26(+0.20)(-0.14) eV for extragalactic origin. The necessary UHEnu flux should be detected in the near future.     

Search for T-violation in neutrino oscillation with the use of muon polarization at a neutrino factory

A possibility to search for T violation in neutrino oscillation with the use of muon polarization is studied. The sensitivity to T violation is examined with various magnitudes of muon polarization as a function of muon energy and long-baseline distances.     

Search for neutrino oscillations at the palo verde nuclear reactors

We report on the initial results from a measurement of the antineutrino flux and spectrum at a distance of about 800 m from the three reactors of the Palo Verde Nuclear Generating Station using a segmented gadolinium-loaded scintillation detector. We find that the antineutrino flux agrees with that predicted in the absence of oscillations excluding at 90% C.L. nu;(e)-nu;(x) oscillations with Deltam(2)>1.12x10(-3) eV(2) for maximal mixing and sin (2)2straight theta>0.21 for large Deltam(2). Our results support the conclusion that the atmospheric neutrino oscillations observed by Super-Kamiokande do not involve nu(e).     

Search for the right-handed boson W R and heavy neutrino

The SU _c (3) ? SU _L(2) ? SU _R(2) ? U(1) left-right symmetric gauge model has been briefly reviewed. The possibility of the detection of signals from the production of the W _R boson in pp-collisions at the Large Hadron Collider has been discussed. Constraints on the masses of the W _R-boson and heavy neutrino obtained by analyzing the recent experimental data from the Compact Muon Solenoid detector with the total energy of collisions E _tot = 8 TeV have been reviewed.     

Search for the neutrino magnetic moment in the nonequilibrium reactor-antineutrino energy spectrum

We study the time evolution of a typical reactor-antineutrino energy spectrum during the reactor operating period and the decay of the residual-antineutrino spectrum after the reactor is stopped. We find that relevant variations in the spectra of soft recoil electrons produced via weak and magnetic $\bar \nu _e e$ scattering can play a significant role in current and planned searches for the neutrino magnetic moment at reactors.