R. Bertoni

Muon ''depth-intensity'' relation measured by the LVD underground experiment and cosmic-ray muon spectrum at sea level

We present the analysis of the muon events with all muon multiplicities collected during 21804 hours of operation of the first LVD tower. The measured angular distribution of muon intensity has been converted to the `depth -- vertical intensity relation in the depth range from 3 to 12 km w.e.. The analysis of this relation allowed to derive the power index,

Upper limit on the prompt muon flux derived from the LVD underground experiment

gamma

Study of single muons with the Large Volume Detector at the Gran Sasso Laboratory

, of the primary all-nucleon spectrum:

The LVD experiment at Gran Sasso

gamma=2.78 pm 0.05

Measurement of the neutron flux produced by cosmic ray muons with LVD at Gran Sasso

. The `depth -- vertical intensity relation has been converted to standard rock and the comparison with the data of other experiments has been done. We present also the derived vertical muon spectrum at sea level.

10 Years Search for Neutrino Bursts with LVD

We present the analysis of the muon events with all muon multiplicities collected during 21804 hours of operation of the first LVD tower. The measured depth-angular distribution of muon intensities has been used to obtain the normalization factor, A, the power index, gamma, of the primary all-nucleon spectrum and the ratio, R_c, of prompt muon flux to that of pi-mesons - the main parameters which determine the spectrum of cosmic ray muons at the sea level. The value of gamma = 2.77 +/- 0.05 (68% C.L.) and R_c<2.0 x 10^-3 (95% C.L.) have been obtained. The upper limit to the prompt muon flux favours the models of charm production based on QGSM and the dual parton model.

Upper limits to low energy

The present study is based on the sample of 2.9×106 single muons observed by the Large Volume Detector (LVD) at the underground Gran Sasso Laboratory during 36 500 live hours from June 1992 to February 1998. We have measured the muon intensity at slant depths from 3 to 20 km w.e. Most events are high-energy downward muons produced by meson decay in the atmosphere. The analysis of these muons has revealed the power index γ of the π and K spectrum: γ=2.76±0.05. The remainders are horizontal muons produced by the neutrino interactions in the rock surrounding the LVD. The value of this flux near 90° is (6.1±2.7)×10−13 cm−2 s−1 sr−1. The results are compared with the Monte Carlo simulations and the world data.

\bar\nu_\mathrm{e}

SummaryThe Large-Volume Detector (LVD) in the Gran Sasso underground Laboratory is a multipurpose detector consisting of a large volume of liquid scintillator (at present 562 tons are in data taking) interleaved with limited-streamer tubes. Several physical problems are investigated with LVD, the major being the search for neutrino bursts from gravitational stellar collapses in our Galaxy. In this paper we discuss some results on cosmic neutrinos and cosmic-ray muons obtained with the first of the five towers of LVD (operational since June 1992) and part of the second tower (operational since June 1994). The results of the search for supernovae neutrinos show that LVD is a neutrino observatory able to detect neutrinos of different flavours from gravitational stellar collapses in all our Galaxy, over a wide range of burst durations. Indeed, the carbon-based liquid-scintillator target gives a unique possibility to directly detect neutral- and charged-currents neutrino interactions with a very good signature. This characteristic of LVD allows us to make an indirect estimate of the neutrino rest mass and of neutrino oscillations from supernovae in our Galaxy. No evidence for burst candidates has been found in the data recorded from June 1992 to March 1995, for a total live time of 682 days and a total exposure of 613 tons per year. We present the results of a time coincidence analysis between low-energy signals, eventually due to neutrinos of different flavours, and γ-ray bursts (GRBs) detected by the BATSE experiment. This search covers the period from June 1993 to March 1995, during which 41 GRBs have been selected from the BATSE data. Since no excess of events in LVD has been found, upper limits on the neutrino fluxes are reported for (νe, p), and for neutral- and charged-currents neutrino interactions of different flavours with the C-nuclei of the scintillator. The muon intensity as a function of slant depth is presented. These measurements, obtained during a live time period of 11.556 hours, cover a slant depths range from about 3000 to about 20 000 hg/cm2 of standard rock and extend over five decades of intensity. An interesting result is that the muon flux is independent of slant depth beyond a depth of about 14 000 hg/cm2 of standard rock, and corresponds to near horizontal muons. This is direct evidence that this flux is due to atmospheric neutrinos interacting in the rock surrounding LVD.