25 research outputs found
IceCube Science
We discuss the status of the kilometer-scale neutrino detector IceCube and
its low energy upgrade Deep Core and review its scientific potential for
particle physics. We subsequently appraise IceCube's potential for revealing
the enigmatic sources of cosmic rays. After all, this aspiration set the scale
of the instrument. While only a smoking gun is missing for the case that the
Galactic component of the cosmic ray spectrum originates in supernova remnants,
the origin of the extragalactic component remains as inscrutable as ever. We
speculate on the role of the nearby active galaxies Centaurus A and M87.Comment: 19 pages, 8 figures; Talk at Discrete 08, Valencia, Spai
The Highest Energy Neutrinos
Measurements of the arrival directions of cosmic rays have not revealed their
sources. High energy neutrino telescopes attempt to resolve the problem by
detecting neutrinos whose directions are not scrambled by magnetic fields. The
key issue is whether the neutrino flux produced in cosmic ray accelerators is
detectable. It is believed that the answer is affirmative, both for the
galactic and extragalactic sources, provided the detector has kilometer-scale
dimensions. We revisit the case for kilometer-scale neutrino detectors in a
model-independent way by focussing on the energetics of the sources. The real
breakthrough though has not been on the theory but on the technology front: the
considerable technical hurdles to build such detectors have been overcome.
Where extragalactic cosmic rays are concerned an alternative method to probe
the accelerators consists in studying the arrival directions of neutrinos
produced in interactions with the microwave background near the source, i.e.
within a GZK radius. Their flux is calculable within large ambiguities but, in
any case, low. It is therefore likely that detectors that are larger yet by
several orders of magnitudes are required. These exploit novel techniques, such
as detecting the secondary radiation at radio wavelengths emitted by neutrino
induced showers.Comment: 16 pages, pdflatex, 7 jpg figures, ICRC style files included.
Highlight talk presented at the 30th International Cosmic Ray Conference,
Merida, Mexico, 200
Diffuse Neutrino and Gamma-ray Emissions of the Galaxy above the TeV
We simulate the neutrino and -ray emissions of the Galaxy which are
originated from the hadronic scattering of cosmic rays (CR) with the
interstellar medium (ISM).
Rather than assuming a uniform CR density, we estimate the spatial
distribution of CR nuclei by means of numerical simulations. We consider
several models of the galactic magnetic field and of the ISM distribution
finding only a weak dependence of our results on their choice. We found that by
extrapolating the predicted -ray spectra down to few GeV we get a good
agreement with EGRET measurements. Then, we can reliably compare our
predictions with available observations above the TeV both for the
-rays and the neutrinos. We confirm that the excesses observed by
MILAGRO in the Cygnus region and by HESS in the Galactic Centre Ridge cannot be
explained without invoking significant CR over-densities in those regions.
Finally, we discuss the perspectives that a km neutrino telescope based in
the North hemisphere has to measure the diffuse emission from the inner Galaxy.Comment: 27 pages, 13 figures. Several figures have been added or replaced. A
new model for the ISM distribution has been considered. Accepted for
publication in JCA
Evidence for TeV Emission from GRB 970417a
Milagrito, a detector sensitive to very high energy gamma rays, monitored the
northern sky from February 1997 through May 1998. With a large field of view
and a high duty cycle, this instrument was well suited to perform a search for
TeV gamma-ray bursts (GRBs). We report on a search made for TeV counterparts to
GRBs observed by BATSE. BATSE detected 54 GRBs within the field of view of
Milagrito during this period. An excess of events coincident in time and space
with one of these bursts, GRB 970417a, was observed by Milagrito. The excess
has a chance probability of of being a fluctuation of the
background. The probability for observing an excess at least this large from
any of the 54 bursts is . No significant correlations were
detected from the other bursts.Comment: 10 pages, 3 figure
TeV Observations of Markarian 501 with the Milagrito Water Cherenkov Detector
The Milagrito water Cherenkov detector near Los Alamos, New Mexico, operated
as a sky monitor at energies of a few TeV between February 1997 and May 1998
including the period of the strong, long-lasting 1997 flare of Markarian 501.
Milagrito served as a test run for the full Milagro detector. An event excess
with a significance of 3.7 sigma from Markarian 501 was observed, in agreement
with expectations.Comment: 10 pages, 3 figures (figure 2 in color). accepted for publication in
ApJ Letter