[en] A large area underground detector with accurate muon tracking and directionality can be used for the search of extraterrestrial sources of high energy neutrinos. The sensitivity of the MACRO detector to possible sources of neutrinos was evaluated with a Monte-Carlo simulation of the neutrino interaction in rock and of the detection in the real apparatus. Two categories of possible neutrino sources are discussed in comparison with the detector sensitivity. Promising candidate objects for this search appear to be the two binary x-ray sources in the southern key Vela X1 and LMC X4, which are known to emit gamma rays up to the 10,000 TeV region

[en] It is conceivable that the recently discovered ceramic superconducting materials, with T_c > 72 K, like the Ba₂YCu₃O_6.9, could be employed in the construction of a new generation of massive low-energy neutrino detectors, without prohibitively sophisticated cryogenic system. In this paper it is discussed the detection of low-energy neutrinos via the coherent neutral-current elastic scattering, with an 'ideal' detector, whose sensivity is quantum limited. It is well known that coherent elastic scattering is the dominant interaction of neutrinos with De Broglie wavelength smaller than nuclear size, or E_ν<<200 MeV/A^1/3, and it is insensitive to the neutrino flavour. Therefore, a measurement of the solar-neutrino flux with this type of detector could give a definitive solution to the solar-neutrino puzzle

[en] The origin of the asymmetry between matter and antimatter that is evident in our part of the Universe is one of the open questions in cosmology, because the CPT symmetry between matter and antimatter seems to be absolutely conserved at microscopic level. We repeat here the classical proofs which exclude the viability of a Universe baryon symmetric on the average, or the observed asymmetry as an initial condition. The current understanding is that the asymmetry should have been dynamically generated before nucleosynthesis, by B, C, and CP-violating processes, acting out of thermodynamical equilibrium, as suggested by Sakharov in the 70's. The physical realizations of these conditions would be possible, in principle, also in the framework of the Standard Model of elementary particles, but the present limits on the mass of the Higgs particle exclude this possibility. Finally we present the model of baryogenesis through leptogenesis, which is allowed by a minimal extension of the Standard Model, which has the appeal of being testable in future long-baseline neutrino oscillation experiments

[en] Short communication

[en] The first Townsend coefficient for Ar-CO₂ based gas mixtures has been measured over a wide range of reduced electric field. The experimental setup and the measurement technique are described here. A linear superposition model has also been successfully applied

No abstract available

[en] The temporal behavior of three new events of modulated optical emission from Cyg X1, detected in July this year, is presented

[en] The general outlines of the gravitational collapse of a massive stellar core and measurable quantities, such as the total energy of the neutrino burst, the spectrum of the neutrinos of each flavor, and the time scale of the burst, are derived from first principles. (H.W.). 8 refs

[en] We have reanalyzed the sensitivity of an underground muon detector to (ν/sub μ/bold-arrow-left-rightν/sub e/) oscillations, taking into account the Wolfenstein, Mikheyev, and Smirnov matter effect. We find that the measurement of the charge of the muons would greatly improve the sensitivity of this type of experiment. Such a measurement would enhance the statistical significance of an eventual oscillation signal and, allowing for a comparison of the μ^- and μ⁺ fluxes, can eliminate the systematic uncertainty upon the absolute normalization of the neutrino flux. We show that a realistic detection system can explore the region in parameter space 3 x 10/sup -3/≤Δm²≤10/sup -1/ eV² and sin²2θ≥0.02, which is well below current accelerator and reactor limits

[en] A numerical solution of the transport equation, based on the iterative method of expansion in order of scattering, is proposed to evaluate the effect of multiple Compton scattering on the cosmic X-ray spectrum from balloon experiments. Computation up to the second order of scattering is performed in the hard X-ray range (10-200 keV). It is shown that this approximation is sufficient to evaluate the X-ray flux at typical balloon atmospherical depths. (orig.)