C. Castagnoli

Experimental Study of Atmospheric Neutrino Flux in the NUSEX Experiment

The fully contained events detected in the NUSEX nucleon stability experiment have been analysed to search for possible anomalies in the fluxes of atmospheric neutrinos. The measured flux of muon neutrinos is in very good agreement with predictions and no anomaly has been found in the ratio between the rate of electron and muon neutrino events.

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.

Observation of a time modulated muon flux in the direction of Cygnus X-3

Abstract The analysis of angular and phase distribution is reported for high energy muons recorded in the NUSEX nucleon decay detector, located in the Mont Blanc tunnel at a depth of about 5000 hg of standard rock. Evidence is found for a signal correlated to the direction and time modulation of Cygnus X-3.

The NUSEX detector

Abstract We present in this paper the characteristics, trigger system and performance of the NUSEX detector, designed to study nucleon stability, running in the Mt. Blanc laboratory.

Nucleon stability, magnetic monopoles and atmospheric neutrinos in the Mont-Blanc experiment

Abstract Ten totally confined events have been found in the Mont-Blanc Nucleon Stability Experiment. While nine can be interpreted as interactions of atmospheric neutrinos, one could be a proton decay. Limits are given for nucleon stability, n- n oscillations, magnetic monopoles and monopole catalysis of nucleon decay.

Measurement of the cosmic ray hadron spectrum up to 30-TeV at mountain altitude: The Primary proton spectrum

The flux of cosmic ray hadrons at the atmospheric depth of 820 g/cm^2 has been measured by means of the EAS-TOP hadron calorimeter (Campo Imperatore, National Gran Sasso Laboratories, 2005 m a.s.l.). The hadron spectrum is well described by a single power law : S(E_h) = (2.25 +- 0.21 +- 0.34(sys)) 10^(-7)(E_h/1000)^(-2.79 +- 0.05) m^(-2) s^(-1) sr^(-1) GeV^(-1) over the energy range 30 GeV-30 TeV. The procedure and the accuracy of the measurement are discussed. The primary proton spectrum is derived from the data by using the CORSIKA/QGSJET code to compute the local hadron flux as a function of the primary proton spectrum and to calculate and subtract the heavy nuclei contribution (basing on direct measurements). Over a wide energy range E_0 = 0.5-50 TeV its best fit is given by a single power law : S(E_0) = (9.8 +- 1.1 +- 1.6(sys)) 10^(-5) (E_0/1000)^(-2.80 +- 0.06) m^(-2) s^(-1) sr^(-1) GeV^(-1). The validity of the CORSIKA/QGSJET code for such application has been checked using the EAS-TOP and KASCADE experimental data by reproducing the ratio of the measured hadron fluxes at the two experimental depths (820 and 1030 g/cm^2 respectively) at better than 10% in the considered energy range.

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.

Energy spectrum and angular distribution of prompt cosmic-ray muons

SummaryThe energy spectrum and angular distribution of atmospheric prompt muons are calculated by using an integral solution for production of charmed particles, their decay and muon transport in the atmosphere. Current experimental information from accelerator and theoretical ideas about charm cross-section and semi-leptonic decay are used to give a reference prompt muon spectrum to compare with that from conventional sources (π and K decay). The obtained differential spectrum has an energy dependence which approaches that of the primary cosmic rays. The integral intensity of prompt muons is equal to the conventional one at about 250 TeV. The angular distribution is found to be practically flat in the range (0÷80)0 irrespective of the muon energy. On the basis of this analysis we estimate that accurate measurements of muon energy spectrum and angular distribution at energies greater than 10 TeV should allow one to obtain useful information regarding charm hadroproduction cross-section in the 100 TeV region.RiassuntoSi calcola uno spettro di muoni pronti per confrontarlo con quello di sorgenti convenzionali (decadimenti da π, K) usando sezioni d’urto di produzione di particelle charmate e decadimenti semileptonici ottenuti da dati di acceleratori e da recenti calcoli teorici. Lo spettro differenziale dei muoni pronti ha una dipendenza dall’energia simile a quella dei raggi cosmici primari. L’intensità integrale dei muoni pronti raggiunge quella convenzionale a circa 250 TeV e la distribuzione angolare è praticamente isotropa nell’intervallo (0÷80)o non dipendendo dall’energia dei muoni. Sulla base di questa analisi noi riteniamo che un’accurata misura della distribuzione angolare e dello spettro in energia dei muoni ad energie maggiori di 10 TeV possano permettere di ottenere utili informazioni sulla sezione d’urto della produzione adronica di particelle charmate nella regione dei 100 TeV.