In spite of the lack of a ”standard” model of the gravitational collapse of a massive star, some features of its dynamics and, in particular, of the correlated neutrino emission appear to be well established. At the end of its burning phase a massive star (M > 8 solar mass) explodes into a supernova, originating a neutron star which cools emitting its binding energy ˜ 3 x 1053 erg mostly in neutrinos. The largest part of this energy, almost equipartitioned among neutrino and antineutrino species, is emitted in the cooling phase. The energy spectra are approximatively a Fermi-Dirac distribution, but with different mean temperatures,
since ne, ne and nt have different couplings (cross sections values) with the stellar matter: Tne < Tne < Tnx
Since the described features of stellar collapses are essentially common to all existing models and lead to rather model independent expectations for supernova neutrinos, the signal observable in LVD, in different reactions and due to different kinds of neutrinos, besides providing astrophysical information on the nature of the collapse, is sensitive to intrinsic n properties, as oscillation of massive neutrinos.
LVD has been continuosly monitoring the whole Galaxy in the search for neutrino bursts from gravitational stellar collapses since 1992. No stellar collapses in our Galaxy have been detected so far.
LVD is involved in the SNEWS (Supernova Early Warning System), which is an international collaboration including all of the current major supernova neutrino detectors. The goal of SNEWS is to provide the astronomical community with a prompt alert of the occurrence of a galactic core collapse event: the neutrino signal indeed will emerge promptly from a supernova while it may take hours for the first photons to be visible.
In addition to its major purpose, the LVD detector allows for other important physics studies, mainly related to cosmic rays. The tracking system design provides good detection efficiency even for tracks near the horizontal, allowing for the study of the muon intensity over a very large range of slant depths up to the plateau region. The combined information from the scintillation counters and the tracking system provides a good measurement of the energy loss of muons per unit path length which has allowed the study of the local muon underground energy spectrum and of characteristics of the deepest component of the penetrating cosmic radiation.
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