966 research outputs found
Auger : A Large Air Shower Array and Neutrino Telescope
Detection of Ultra High Energy Neutrinos (UHEN), with energy above 0.l EeV
(10**18 eV) is one of the most exciting challenges of high energy astrophysics
and particle physics. In this article we show that the Auger Observatories,
built to study ultra high energy cosmic rays, are one of the most sensitive
neutrino telescopes that will be available in the next decade. Furthermore, we
point out that the Waxman-Bahcall upper bound for high energy neutrino fluxes
below 1 EeV turns into a lower bound above a few EeV. In this framework and
given the experimental evidences for nu_mu nu_tau oscillations with large
mixing, we conclude that observation of Tau UHEN in the southern Auger
Observatory should most certainly occur within the next five years.Comment: 6 pages, 6 figures, 1 table. Talk given at the neutrino 2002
conference. To be published in Nuclear Physics B (Proceedings Supplement)
Corrected misplaced WB limit in Figure
Neutrinos and the Highest Energy Cosmic Rays
Observation of Ultra High Energy Cosmic Rays (UHECR) -whose energy exceeds
eV- is still a puzzle for modern astrophysics. The transfer of more than
16 Joules to a microscopic particle can hardly be achieved, even in the most
powerful cosmic accelerators such as AGN's, GRB's or FR-II radio galaxy lobes.
Potential sources must also lie within 100 Mpc of the Earth as the interaction
length of protons, nuclei or photons is less than 10Mpc. However no visible
counterpart of those sources has been observed. Calling upon new physics such
as Topological Defect interactions or Super Massive Relic Particle decays is
therefore very tempting, but such objects are yet to be proven to exist. Due to
the very low flux of UHECR only very large dedicated experiments, such as the
Auger observatories, will allow to shed some light on the origin of those
cosmic rays. In this quest neutrinos, if they can be detected, are an
invaluable messengers of the nature of the sources.Comment: Talk Given at the Neutrino 2000 COnference. Sudbury, Toronto June
12-17 2000 7 pages, 8 figure
Note on the Origin of the Highest Energy Cosmic Rays
In this note we argue that the galactic model chosen by E.-J. Ahn, G.
Medina-Tanco, P.L. Bierman and T. Stanev in their paper discussing the origin
of the highest energy cosmic rays, is alone responsible for the focussing of
positive particles towards the North galactic pole. We discuss the validity of
this model, in particular in terms of field reversals and radial extensions. We
conclude that with such a model one cannot retreive any directional information
from the observed direction of the cosmic rays. In particular one cannot
identify point sources at least up to energies of about 200 EeV. Therefore the
apparent clustering of the back-traced highest energy cosmic rays observed to
date cannot be interpreted as an evidence for a point source nor for the
identification of M87, which happens to be close to the North pole, as being
such a source.Comment: 3 pages, 2 figure
Ultrahigh Energy Cosmic Rays
This is a review of the most resent results from the investigation of the
Ultrahigh Energy Cosmic Rays, particles of energy exceeding 10 eV. After
a general introduction to the topic and a brief review of the lower energy
cosmic rays and the detection methods, the two most recent experiments, the
High Resolution Fly's Eye (HiRes) and the Southern Auger Observatory are
described. We then concentrate on the results from these two experiments on the
cosmic ray energy spectrum, the chemical composition of these cosmic rays and
on the searches for their sources. We conclude with a brief analysis of the
controversies in these results and the projects in development and construction
that can help solve the remaining problems with these particles.Comment: 40 pages, 27 figure
Physics of Extremely High Energy Cosmic Rays
Over the last third of the century, a few tens of events, detected by
ground-based cosmic ray detectors, have opened a new window in the field of
high-energy astrophysics. These events have macroscopic energies, unobserved
sources, an unknown chemical composition and a production and transport
mechanism yet to be explained. With a flux as low as one particle per century
per square kilometer, only dedicated detectors with huge apertures can bring in
the high-quality and statistically significant data needed to answer those
questions. In this article, we review the present status of the field both from
an experimental and theoretical point of view. Special attention is given to
the next generation of detectors devoted to the thorough exploration of the
highest energy rangesComment: 43 pages, 12 figures, submitted to International Journal of Modern
Physics
Ultra High Energy Cosmic Rays and the Auger Observatory
In this proceeding we present the construction status and the performances of
the Pierre Auger Observatory together with the first results obtained with our
initial 18 month of data. In particular, we discuss our search for anisotropy
near the Galactic Center, our limit on the photon fraction at the highest
energies and our first estimate of the cosmic ray spectrum above 3 EeV. All of
the material presented in this proceeding was extracted from the numerous Auger
contributions to the 29th ICRC proceedings.Comment: 12 pages, 7 figures. Proceedings of the PIC 2005 conference. Praha,
July 200
Establishing The GZK Cutoff With Ultra High Energy Tau Neutrinos
The cosmic ray spectrum has been shown to extend well beyond 10^20 eV. With
nearly 20 events observed in the last 40 years, it is now established that
particles are accelerated or produced in the universe with energy near 10^21
eV. In all production models neutrinos and photons are part of the cosmic ray
flux. In acceleration models (bottom-up models), they are produced as
secondaries of the possible interactions of the accelerated charged particle,
in direct production models (top-down models) they are a dominant fraction of
the decay chain. In addition, hadrons above the GZK threshold energy will also
produce, along their path in the Universe, neutrinos and photons as secondaries
of the pion photo-production processes. Therefore, photons and in particular
neutrinos, are very distinctive signatures of the nature and distribution of
the potential sources of ultra high energy cosmic rays. In the following we
expose the identification capabilities of the Auger observatories. In the
hypothesis of nu_mu-->nu_tau oscillations with full mixing, special emphasis is
placed on the observation of tau neutrinos, with which Auger is able to
establish the GZK cutoff as well as to provide a strong and model independant
constraint on the top-down sources of ultra high energy cosmic rays.Comment: Talk given at the International Workshop on Observing Ultra High
Energy Cosmic Rays From Space and Earth, Puebla 2000 (Mexico). 15 pages, 9
figure
Theoretical and Experimental Topics on Ultra High Energy Cosmic Rays
Since their first observation in 1962, the existence of Ultra High Energy
Cosmic Rays (UHECR) remains a mystery in modern astrophysics. Those cosmic
rays, with energies well above 50 EeV (eV), can hardly be
accelerated, even in the most active parts of our universe such as FR-II radio
galaxies or AGNs, nor can they travel on distances larger than 100 Mpc. In the
following some of the production and acceleration models for UHECR are reviewed
and some of the transport issues are exposed. Finally the detection and
identification on Earth of those ``cosmic bullets'' are presented.Comment: 46 pages, 16 figures. Lecture given at the XXVIII International
Meeting on Fundamental Physics, Sanlucar de Barameda, Cadiz Spain, 14-18
February 200
A model for the time uncertainty measurements in the Auger surface detector array
The precise determination of the arrival direction of cosmic rays is a
fundamental prerequisite for the search for sources or the study of their
anisotropies on the sky. One of the most important aspects to achieve an
optimal measurement of these directions is to properly take into account the
measurement uncertainties in the estimation procedure. In this article we
present a model for the uncertainties associated with the time measurements in
the Auger surface detector array. We show that this model represents well the
measurement uncertainties and therefore provides the basis for an optimal
determination of the arrival direction. With this model and a description of
the shower front geometry it is possible to estimate, on an event by event
basis, the uncertainty associated with the determination of the arrival
directions of the cosmic rays
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