arXiv subjects
Publications and source records attributed to T. Montaruli.
We use a sample of 990 upward-going muons, induced primarily by atmospheric neutrinos, to search for neutrinos of astrophysical origin. No evidence has been found using the event direction information. Flux limits of the order of 10^-15 cm^-2 s^-1 are imposed on current models for candidate point-sources. A space-time correlation search has been undertaken between 2328 BATSE gamma ray bursts (GRBs) and MACRO upward-going muons.
We present updated results on the search for a neutrino signal from the core of the Earth and of the Sun induced by Weakly Interacting Massive Particles (WIMPs). In this paper we concentrate on neutralinos as WIMP candidates. The 971 and 642 events used respectively for the search from the Sun and from the Earth are compatible with the background of atmospheric neutrinos. Consequently we calculate flux limits for various search cones around these sources. Limits as a function of the neutralino mass are given and compared to the supersymmetric (SUSY) models.
We look for space-time correlations between 2233 gamma-bursts in the Batse Catalogs and 894 upward-going muons produced by neutrino interactions in the rock below or inside MACRO. Considering a search cone of 10 degrees around GRB directions and a time window of 200 s we find 0 events to be compared to 0.035 expected background events due to atmospheric neutrinos. The corresponding upper limit (90% c.l.) is 0.87 * 10^-9 cm^-2 upward-going muons per average burst.
MACRO can detect three topologies of neutrino induced events, corresponding to different parent neutrino energies. The most numerous sample is made of upward throughgoing muons induced by atmospheric neutrinos of average energy 100 GeV. We have observed less events than expected events and the observed zenith distribution does not fit the expected one in the no-oscillation hypothesis, giving a maximum probability of 0.1 percent. Considering the neutrino (numu-nutau) oscillation hypothesis the best probability (17 percent) is obtained for maximum mixing and difference of square masses of a few times 10-3 eV2. The other detected samples are due to internally produced events and upward-going stopping muons, corresponding to an average neutrino energy of around 4 GeV. The results concerning these lower energy sample show a deficit and a shape of the angular distributions in agreement with that predicted by the oscillation model suggested by the higher energy sample. No evidence of a neutrino signal due to dark matter particles in the direction of the core of the Earth and of the Sun has been found among the background due to atmospheric neutrinos and limits have been set. The neutralino hypothesis is investigated and limits on its mass are given.
The design of an Airwatch type space mission can greatly benefit from a flexible simulation code for establishing the values of the main parameters of the experiment. We present here a code written for this purpose. The cosmic ray primary spectrum at very high energies, the atmosphere modelling, the fluorescence yield, the photon propagation and the detector response are taken into account in order to optimize the fundamental design parameters of the experiment, namely orbit height, field of view, mirror radius, number of pixels of the focal plane, threshold of photo-detection. The optimization criterion will be to maximize counting rates versus mission cost, which imposes limits both on weight and power consumption. Preliminary results on signals with changing energy and zenith angle of incident particles are shown.