97 research outputs found
Simulation of the Cosmic Ray Moon Shadow in the Geomagnetic field
An accurate MonteCarlo simulation of the deficit of primary cosmic rays in
the direction of the Moon has been developed to interpret the observations
reported in the TeV energy region until now. Primary particles are propagated
trough the geomagnetic field in the Earth-Moon system. The algorithm is
described and the contributions of the detector resolution and of the
geomagnetic field are disentangled.Comment: 4 pages, 5 figures, Contribution to the 31st ICRC, Lodz, Poland, July
200
Mutually compensative pseudo solutions of primary energy spectra in the knee region
The problem of the uniqueness of solutions during the evaluation of primary
energy spectra in the knee region using an extensive air shower (EAS) data set
and the EAS inverse approach is investigated. It is shown that the unfolding of
primary energy spectra in the knee region leads to mutually compensative pseudo
solutions. These solutions may be the reason for the observed disagreements in
the elementary energy spectra of cosmic rays in the 1-100 PeV energy range
obtained from different experiments.Comment: Accepted for publication in Astroparticle Physic
Cosmic-ray electron injection from the ionization of nuclei
We show that the secondary electrons ejected from the ionization of heavy
ions can be injected into the acceleration process that occurs at supernova
remnant shocks. This electron injection mechanism works since ions are ionized
during the acceleration when they move already with relativistic speed, just
like ejected electrons do. Using the abundances of heavy nuclei measured in
cosmic rays at Earth, we estimate the electron/proton ratio at the source to be
~10^-4, big enough to account for the nonthermal synchrotron emission observed
in young SNRs. We also show that the ionization process can limit the maximum
energy that heavy ions can reach.Comment: 4 pages, 1 figure, accepted for publication in Physical Review
Letter
Cosmic ray photodisintegration and the knee of the spectrum
We explore in some detail the scenario proposed to explain the observed knee
of the cosmic ray (CR) spectrum as due to the effects of photodisintegration of
the CR nuclei by interactions with optical and soft UV photons in the source
region. We show that the photon column densities needed to explain the
experimental data are significantly lower than those obtained in previous
estimations which neglected multinucleon emission in the photodisintegration
process. We also treat more accurately the photodisintegration thresholds, we
discuss the effects of photopion production processes and the neutron escape
mechanism, identifying the physical processes responsible for the qualitative
features of the results. This scenario would require the CR nuclei to traverse
column densities of eV/cm after
being accelerated in order to reproduce the observed knee, and predicts that
the CR composition should become lighter above eV.Comment: 17 pp. Comments and references added. To appear in Astroparticle
Physic
Simulation of neutrino and charged particle production and propagation in the atmosphere
A precise evaluation of the secondary particle production and propagation in
the atmosphere is very important for the atmospheric neutrino oscillation
studies. The issue is addressed with the extension of a previously developed
full 3-Dimensional Monte-Carlo simulation of particle generation and transport
in the atmosphere, to compute the flux of secondary protons, muons and
neutrinos. Recent balloon borne experiments have performed a set of accurate
flux measurements for different particle species at different altitudes in the
atmosphere, which can be used to test the calculations for the atmospheric
neutrino production, and constrain the underlying hadronic models. The
simulation results are reported and compared with the latest flux measurements.
It is shown that the level of precision reached by these experiments could be
used to constrain the nuclear models used in the simulation. The implication of
these results for the atmospheric neutrino flux calculation are discussed.Comment: 11 pages, 9 figure
New results on source and diffusion spectral features of Galactic cosmic rays: I- B/C ratio
In a previous study (Maurin et al., 2001), we explored the set of parameters
describing diffusive propagation of cosmic rays (galactic convection,
reacceleration, halo thickness, spectral index and normalization of the
diffusion coefficient), and we identified those giving a good fit to the
measured B/C ratio. This study is now extended to take into account a sixth
free parameter, namely the spectral index of sources. We use an updated version
of our code where the reacceleration term comes from standard minimal
reacceleration models. The goal of this paper is to present a general view of
the evolution of the goodness of fit to B/C data with the propagation
parameters. In particular, we find that, unlike the well accepted picture, and
in accordance with our previous study, a Kolmogorov-like power spectrum for
diffusion is strongly disfavored. Rather, the analysis points towards
along with source spectra index . Two
distinct energy dependences are used for the source spectra: the usual
power-law in rigidity and a law modified at low energy, the second choice being
only slightly preferred. We also show that the results are not much affected by
a different choice for the diffusion scheme. Finally, we compare our findings
to recent works, using other propagation models. This study will be further
refined in a companion paper, focusing on the fluxes of cosmic ray nuclei.Comment: 32 pages, 13 figures, accepted in A&
Origin of the highest energy cosmic rays observed
Introducing a simple Galactic wind model patterned after the solar wind we
show that back-tracing the orbits of the highest energy cosmic events suggests
that they may all come from the Virgo cluster, and so probably from the active
radio galaxy M87. This confirms a long standing expectation. Those powerful
radio galaxies that have their relativistic jets stuck in the interstellar
medium of the host galaxy, such as 3C147, will then enable us to derive limits
on the production of any new kind of particle, expected in some extensions of
the standard model in particle physics. New data from HIRES will be crucial in
testing the model proposed here.Comment: At TAUP99, the 6th international workshop on topics in Astroparticle
Physics and Underground Physics, College de France, Eds. J. Dumarchez, M.
Froissart, D. Vignaud, (Sep 1999
The Galactic magnetic field and propagation of ultra-high energy cosmic rays
The puzzle of ultra-high energy cosmic rays (UHECRs) still remains
unresolved. With the progress in preparation of next generation experiments
(AUGER, EUSO, OWL) grows also the importance of directional analysis of
existing and future events. The Galactic magnetic field (GMF) plays the key
role in source identification even in this energy range. We first analyze
current status of our experimental and theoretical knowledge about GMF and
introduce complex up-to-date model of GMF. Then we present two examples of
simple applications of influence of GMF on UHECR propagation. Both examples are
based on Lorentz equation solution. The first one is basic directional analysis
of the incident directions of UHECRs and the second one is a simulation of a
change of chemical composition of CRs in the energy range 10^13 - 10^19 eV. The
results of these simple analyses are surprisingly rich - e.g. the rates of
particle escape from the Galaxy or the amplifications of particle flux in
specific directions.Comment: 10 pages, 7 figures, accepted for publication in A&
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