140 research outputs found
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
Phenomenology of atmospheric neutrinos
The relevance of the data concerning upward--going muons for the solution of
the atmospheric neutrino problem is stressed. In particular, their inclusion in
the analysis confirms the goodness of the neutrino oscillation hypothesis and
allows to exclude some alternative, exotic explanations such as neutrino decay,
flavour changing neutral currents, violations of the equivalence principle (at
least in their simplest forms), and also to discriminate, in principle, between
different neutrino oscillation models (nu_mu nu_tau versus nu_mu nu_s),
because of the difference in the matter effects.Comment: Talk presented at "The 17th International Workshop on Weak
Interactions and Neutrinos (WIN99)," Capetown, South Africa, Jan. 1999, Latex
5 pages 3 figure
Multiple Parton Interactions in Hadron Collisions and Diffraction
Hadrons are composite objects made of quarks and gluons, and during a
collision one can have several elementary interactions between the
constituents. These elementary interactions, using an appropriate theoretical
framework, can be related to the total and elastic cross sections. At high c.m.
energy it also becomes possible to identify experimentally a high pt subset of
the parton interactions and to study their multiplicity distribution.
Predictions of the multiple interactions rates are difficult because in
principle one needs to have a knowledge of the correlated Parton Distribution
Functions that describe the probability to find simultaneously different
partons in different elements of phase space. In this work we address this
question and suggest a method to describe effectively the fluctuations in the
instantaneous configuration of a colliding hadron. This problem is intimately
related to the origin of the inelastic diffractive processes. We present a new
method to include the diffractive cross section in an eikonal formalism that is
equivalent to a multi-channel eikonal. We compare with data and present an
extrapolation to higher energy.Comment: 34 pages, 9 figure
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