948 research outputs found
Muon Detection of TeV Gamma Rays from Gamma Ray Bursts
Because of the limited size of the satellite-borne instruments, it has not
been possible to observe the flux of gamma ray bursts (GRB) beyond GeV energy.
We here show that it is possible to detect the GRB radiation of TeV energy and
above, by detecting the muon secondaries produced when the gamma rays shower in
the Earth's atmosphere. Observation is made possible by the recent
commissioning of underground detectors (AMANDA, the Lake Baikal detector and
MILAGRO) which combine a low muon threshold of a few hundred GeV or less, with
a large effective area of 10^3 m^2 or more. Observations will not only provide
new insights in the origin and characteristics of GRB, they also provide
quantitative information on the diffuse infrared background.Comment: Revtex, 12 pages, 3 postscript figures, uses epsfig.st
TeV String State Excitation via High Energy Cosmic Neutrinos
We construct the open-string scattering amplitudes for neutrino-gluon
collisions and evaluate the high energy neutrino-nucleon scattering cross
section via string state excitations in the TeV string-scale scenario. We find
that the neutrino-gluon scattering is the dominant contribution, 5-10 times
larger than neutrino-quark processes, though black hole production may be
larger than the string contribution at higher energies. We illustrate the
observability of the string signal at the Auger Observatory and the IceCube
neutrino telescope for a string scale about 1 TeV.Comment: version to appear in PL
Measuring the Spectra of High Energy Neutrinos with a Kilometer-Scale Neutrino Telescope
We investigate the potential of a future kilometer-scale neutrino telescope
such as the proposed IceCube detector in the South Pole, to measure and
disentangle the yet unknown components of the cosmic neutrino flux, the prompt
atmospheric neutrinos coming from the decay of charmed particles and the
extra-galactic neutrinos, in the 10 TeV to 1 EeV energy range.
Assuming a power law type spectra,
, we quantify the discriminating
power of the IceCube detector and discuss how well we can determine magnitude
() as well as slope () of these two components of the high
energy neutrino spectrum, taking into account the background coming from the
conventional atmospheric neutrinos.Comment: 21 pages, 7 figure
IceCube-Plus: An Ultra-High Energy Neutrino Telescope
While the first kilometer-scale neutrino telescope, IceCube, is under
construction, alternative plans exist to build even larger detectors that will,
however, b e limited by a much higher neutrino energy threshold of 10 PeV or
higher rather than 10 to 100 GeV. These future projects detect radio and
acoustic pulses as w ell as air showers initiated by ultra-high energy
neutrinos. As an alternative, we here propose an expansion of IceCube, using
the same strings, placed on a gri d with a spacing of order 500 m. Unlike other
proposals, the expanded detector uses methods that are understood and
calibrated on atmospheric neutrinos. Atmosp heric neutrinos represent the only
background at the energies under consideratio n and is totally negligible.
Also, the cost of such a detector is understood. We conclude that supplementing
the 81 IceCube strings with a modest number of addi tional strings spaced at
large distances can almost double the effective volume of the detector.
Doubling the number of strings on a 800 m grid can deliver a d etector that
this a factor of 5 larger for horizontal muons at modest cost.Comment: Version to be published in JCA
Flavor conversion of cosmic neutrinos from hidden jets
High energy cosmic neutrino fluxes can be produced inside relativistic jets
under the envelopes of collapsing stars. In the energy range E ~ (0.3 - 1e5)
GeV, flavor conversion of these neutrinos is modified by various matter effects
inside the star and the Earth. We present a comprehensive (both analytic and
numerical) description of the flavor conversion of these neutrinos which
includes: (i) oscillations inside jets, (ii) flavor-to-mass state transitions
in an envelope, (iii) loss of coherence on the way to observer, and (iv)
oscillations of the mass states inside the Earth. We show that conversion has
several new features which are not realized in other objects, in particular
interference effects ("L- and H- wiggles") induced by the adiabaticity
violation. The neutrino-neutrino scattering inside jet and inelastic neutrino
interactions in the envelope may produce some additional features at E > 1e4
GeV. We study dependence of the probabilities and flavor ratios in the
matter-affected region on angles theta13 and theta23, on the CP-phase delta, as
well as on the initial flavor content and density profile of the star. We show
that measurements of the energy dependence of the flavor ratios will, in
principle, allow to determine independently the neutrino and astrophysical
parameters.Comment: 56 pages, 19 figures. Minor changes. Accepted by JHEP
From AMANDA to IceCube
The first string of the neoteric high energy neutrino telescope IceCube
successfully began operating in January 2005. It is anticipated that upon
completion the new detector will vastly increase the sensitivity and extend the
reach of AMANDA to higher energies. A discussion of the IceCube's discovery
potential for extra-terrestrial neutrinos, together with the prospects of new
physics derived from the ongoing AMANDA research will be the focus of this
paper. Preliminary results of the first antarctic high energy neutrino
telescope AMANDA searching in the muon neutrino channel for localized and
diffuse excess of extra-terrestrial neutrinos will be reviewed using data
collected between 2000 and 2003. Neutrino flux limits obtained with the
all-flavor dedicated UHE and cascade analyses will be described. A first
neutrino spectrum above one TeV in agreement with atmospheric neutrino flux
expectations and no extra-terrestrial contribution will be presented, followed
by a discussion of a limit for neutralino CDM candidates annihilating in the
center of the Sun.Comment: 15 pages, 8 figures Invited talk contribution at 5th International
Conference on Non-accelerator New Physics (NANP 05), Dubna, Russia, 20-25 Jun
200
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The Pierre Auger Observatory scaler mode for the study of solar activity modulation of galactic cosmic rays
Since data-taking began in January 2004, the Pierre Auger Observatory has been recording the count rates of low energy secondary cosmic ray particles for the self-calibration of the ground detectors of its surface detector array. After correcting for atmospheric effects, modulations of galactic cosmic rays due to solar activity and transient events are observed. Temporal variations related with the activity of the heliosphere can be determined with high accuracy due to the high total count rates. In this study, the available data are presented together with an analysis focused on the observation of Forbush decreases, where a strong correlation with neutron monitor data is found
Cosmic UHE Neutrino Signatures
Utilizing the unique and reliable ultrasmall-- predictions of the
dynamical (radiative) parton model, nominal event rates and their detailed
energy dependence caused by a variety of cosmic UHE neutrino fluxes are
calculated and analyzed. In addition, maximal Regge--model inspired small--
structure functions are employed for obtaining optimal rates which do not
necessarily require `new' physics interpretations. Upward event
rates are estimated by taking into account total and nadir--angle dependent
regeneration effects due to neutral current interactions. For exploring
extragalactic neutrino sources at highest energies
(\raisebox{-0.1cm}{} GeV) with modern (future)
ground--level telescopes, we analyze horizontal air shower event rates and
shower events caused by Earth--skimming tau--neutrinos, in particular their
detailed shower-- and cosmic neutrino--energy dependence. As an illustration of
`new physics' implications we estimate the relevant horizontal air shower event
rates due to spin--2 Kaluza--Klein `graviton' exchanges in neutral current
neutrino--quark and neutrino--gluon interactions at low TeV--scales.Comment: 3 figures changed, discussions and references adde
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