The lifetime of cosmic rays in the Milky Way

The most reliable method to estimate the residence time of cosmic rays in the Galaxy is based on the study of the suppression, due to decay, of the flux of unstable nuclei such as beryllium-10, that have lifetime of appropriate duration. The Cosmic Ray Isotope Spectrometer (CRIS) collaboration has measured the ratio between the fluxes of beryllium-10 and beryllium-9 in the energy range E_0 \simeq 70-145 MeV/nucleon, and has used the data to estimate an escape time tau_{ esc} = 15.0 +- 1.6 Myr. This widely quoted result has been obtained in the framework of a simple leaky-box model where the distributions of escape time and age for stable particles in the Galaxy are identical and have exponential form. In general, the escape time and age distributions do not coincide, they are not unique (because they depend on the injection or observation point), and do not have a simple exponential shape. It is therefore necessary to discuss the measurement of the beryllium ratio in a framework that is more general and more realistic than the leaky-box model. In this work we compute the escape time and age distributions of cosmic rays in the Galaxy in a model based on diffusion that is much more realistic than the simple leaky-box, but that remains sufficiently simple to have exact analytic solutions. Using the age distributions of the model to interpret the measurements of the beryllium-10 suppression, one obtains a cosmic ray residence time that is significantly longer (a factor 2 to 4 depending on the extension of the cosmic ray halo) than the leaky-box estimate. This revised residence time implies a proportional reduction of the power needed to generate the galactic cosmic rays.Comment: Latex, 21 pages, 14 figure

Cosmic Rays, Gamma rays, Neutrinos and Gravitational Waves

This paper discusses the relation between the study of the fluxes of cosmic rays, gamma rays and neutrinos, and the connection of these observations with the newly born field of gravitational wave astronomy.Comment: 6 pages, 2 figures. Proceedings of workshop SCINEGHE 201

Proposal to look for an up/down asymmetry in atmospheric neutrinos beyond Multi-GeV region with existing experimental data

We discuss a possible test of neutrino oscillation hypothesis by proposing the combined analysis of high energy atmospheric neutrino induced muon events that have been detected around horizontal direction in the Kolar Gold Field (KGF) underground site and below the horizontal direction by many large detectors such as Super-Kamiokande and MACRO. Up/down asymmetry obtained using contained events recorded by detectors at Kamioka site probes low energy region of atmospheric neutrino whereas, the suggested method probes high energy neutrinos. It mainly depends on the observations and it is free of uncertainties in neutrino flux, interaction cross section etc. In this paper we demonstrate that the method is sensitive to a region of oscillation parameter space that explains all the features of atmospheric neutrino data in the Super-Kamiokande detector; the limiting factor being the statistical strength of the KGF observations. This method provides the only way to study the up/down asymmetry beyond Multi-GeV region which is yet to be measured experimentally.Comment: revtex, 6 pages with 3 eps figures. Error introduced by the different low-energy thresholds assessed, conclusion unchange

Uncertainties on Atmospheric Neutrino Flux Calculations

The strong evidence of new physics coming from atmospheric neutrino experiments has motivated a series of critical studies to test the robustness of the available flux calculations. In view of a more precise determination of the parameters of new physics, new and more refined flux calculations are in progress. Here we review the most important sources of theoretical uncertainties which affect these computations, and the attempts currently under way to improve them.Comment: Extended version of talk given at NOW2000, Conca Specchiulla, Otranto, Italy, Sep. 2000 Fig. 2 has been replace

The geometry of atmospheric neutrino production

The zenith angle distributions of atmospheric neutrinos are determined by the possible presence of neutrino oscillations and the combination of three most important contributions: (1) geomagnetic effects on the primary cosmic rays, that suppress the primary flux in the Earth's magnetic equatorial region, (2) the zenith angle dependence of the neutrino yields, due to the fact that inclined showers produce more neutrinos, and (3) geometrical effects due to the spherical shell geometry of the neutrino production volume. The last effect has been recognized only recently and results in an important enhancement of the flux of sub--GeV neutrinos for horizontal directions. In this work we discuss the geometrical effect and its relevance in the interpretation of the atmospheric neutrino data.Comment: 26 pages, 11 figure