G. Bologna

On the event observed in the Mont Blanc Underground Neutrino Observatory during the occurrence of supernova 1987A

We discuss here the characteristics of the event detected in the Mont Blanc Underground Neutrino Observatory on February 23, 1987, consisting of 5 interactions recorded during 7s. The measured energies of the 5 pulses, the duration of the burst, and the advance of the detection time in comparison with the first optical observations give evidence that the event can be explained in terms of detection of neutrinos emitted during the stellar collapse in the Large Magellanic Cloud.

Limits on low-energy neutrino fluxes with the Mont Blanc liquid scintillator detector

Abstract The LSD liquid scintillation detector has been operating since 1985 as an underground neutrino observatory in the Mont Blanc Laboratory with the main objective of detecting antineutrino bursts from collapsing stars. In August 1988 the construction of an additional lead and borex paraffin shield considerably reduced the radioactive background and increased the sensitivity of the apparatus. In this way the search for steady fluxes of low-energy neutrinos of different flavours through their interactions with free protons and carbon nuclei of the scintillator was made possible. No evidence for a galactic collapse was observed during the whole period of measurement. The corresponding 90% c.l. upper limit on the galactic collapses rate is 0.45 y −1 for a burst duration of ΔT ⩽ 10 s. After analysing the last 3 years data, the following 90% c.l. upper limits on the steady neutrino and antineutrino fluxes were obtained: Φ( \ gn e ) 4 \ gn e s −1 cm −2 9 ⩽ E ν ⩽ 50MeV Φ( \ gn e ) 3 \ gn e s −1 cm −2 20 ⩽ E ν ⩽ 50MeV Φ(ν e ) 3 ν e s −1 cm −2 25 ⩽ E ν ⩽ 50 MeV Φ(ν μ + τ ) 7 ν μ + τ s −1 cm −2 20 ⩽ E ν ⩽ 100 MeV Φ( \ gn μ + τ ) 7 \ gn μ + τ s −1 cm −2 20 ⩽ E ν ⩽ 100 MeV In particular comparing the obtained upper limit on the \ gn e flux for 9 ⩽ E ν ⩽ 20 MeV to the solar ν e flux predicted by the standard solar model in the same range of energy, we can exclude the possibility that more than 6.3% of the solar ν e s flux can change to \ gn e . Finally the first limits on the flux of relic supernova neutrinos of all flavours as a function of the neutrino sea temperature are presented.

Comments on the Two Events Observed in Neutrino Detectors during the Supernova 1987a Outburst

Before optical detection of supernova SN 1987a, two events, separated in time by 4.72 hours, have been detected in underground laboratories: the first in the Mont Blanc Underground Neutrino Observatory (UNO), the second in Kamiokande II. In this letter we wish to emphasize that these results are not contradictory from the experimental point of view, and can be explained within reasonable theoretical expectations.

Coincidences among the data recorded by the Baksan, Kamioka and Mont Blanc underground neutrino detectors, and by the Maryland and Rome gravitational-wave detectors during Supernova 1987 A

SummaryThe data recorded with the neutrino detectors at Mont Blanc, Kamioka, Baksan and with the gravitational-wave detectors in Maryland and Rome have been analysed searching for correlations associated with SN 1987 A, without presuming or excluding hypotheses for correlations due to neutrinos and gravitational waves. The statistical analysis has been based on a previous analysis that showed a correlation among Maryland, Rome and Mont Blanc with a probability to be accidental less than 10−5. Independent correlations are found during a period of one or two hours, around the Mont Blanc 5ν burst (2h 52 min 36 s UT), among the various sets of data: Mont Blanc-Baksan with a probability to be accidental of the order ofp∼4·10−3, Mont Blanc-Kamioka withp∼4·10−3, Maryland-Rome-Kamioka withp∼5·10−4, Maryland-Rome-Baksan withp∼5·10−2. It is remarkable that the events from all the neutrino detectors follow the signals from the g.w. detectors by a time of the order of 1/2 or 1 s. At present we will not give a physical interpretation of the observed correlations which have strong statistical significance.

Correlation Analysis of the Data Recorded by the Baksan, Kamioka, and Mont Blanc Detectors during SN 1987A

Results are presented on the correlation analysis of data recorded by the Baksan, Kamioka, and Mont Blanc underground detectors during the explosion of the SN 1987. The analysis was performed in order to reinvestigate the observations of two burst of several pulses each occurring several hours before first optical observations. The Mont Blanc computer detected a burst of five pulses about 8 hrs before the first optical observation, followed by a second burst of three pulses about 2 hrs later; Kamioka and Baksan reported observations of a burst made by eleven and five pulses, respectively, delayed by 4.7 hrs in comparison with the Mont Blanc burst. The results of the analysis strongly suggest that the event was real, occurring a few hours before the first optical observation of SN 1987A. 9 refs.

A Search on 1.8 MeV Neutral-Particle Photoproduction in a QED Strong Field

We give upper bounds on the photoproduction in overcritical electric fields of a neutral light boson which could explain the correlated e+e- production seen at GSI-Darmstadt in heavy-ion-atom collisions.

On the neutrino burst from SN 1987a detected in the Mt. Blanc LSD experiment

In this paper we discuss the event, consisting of 5 interactions recorded during 7 seconds, detected in the Mont Blanc Underground Neutrino Observatory (UNO) on February 23, 1987. The updated pulse amplitudes, and the background imitation probability of the event are reported. It is also shown that some interactions recorded at the same time in other underground experiments, with lower detection efficiency, are consistent with the Mont Blanc event.

Search for low-energy νe, μ, τ and\(\bar \nu _{e,\mu ,\tau } \) in coincidence with BATSE gamma-ray burstsin coincidence with BATSE gamma-ray bursts

SummarySince neutrinos and gamma-rays productions are often associated in many astrophysical processes, the detection of neutrinos in correlation with γ-ray bursts (GRBs) could be a very important step towards the discovery of the sources of these events. A search for low-energy neutrinos of all flavours in correlation with ≈ 200 γ-ray bursts detected by BATSE aboard the Compton Observatory has been performed by the LSD (Liquid-Scintillator Detector) neutrino telescope. This kind of telescope, differently from the water Čerenkov detectors, is also sensitive to νμ, τ and

Data Analysis in Neutrino Astronomy

\bar \nu _{\mu , \tau }