410 research outputs found
Air Shower Measurements in the Primary Energy Range from PeV to EeV
Recent results of advanced experiments with sophisticated measurements of
cosmic rays in the energy range of the so called knee at a few PeV indicate a
distinct knee in the energy spectra of light primary cosmic rays and an
increasing dominance of heavy ones towards higher energies. This leads to the
expectation of knee-like features of the heavy primaries at around 100 PeV. To
investigate in detail this energy region several new experiments are or will be
devised.Comment: 4 pages; submitted to Proceedings of 2nd Workshop on TeV
Astrophysics, Aug 28-31, 2006, Madison, W
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
Foreseeing Neutrino spectra in Deep Core
Atmospheric muon neutrino in Deep Core (whose rate and spectra might be soon
available) should exhibit a suppression (due to tens GeV up-going muon neutrino
converted into tau flavor) that must be imprinted in out-coming rate spectra.
We estimate here our independent muon neutrino spectra based on SK and its
projected record on Deep Core Channels. Our estimate (based on cosmic rays,
muon records and tested Super-Kamiokande (SK) data) differs both in shape and
in rate from other previous published spectra. The expected rate might exhibit
a minimum near channel 6 of Deep Core strings and it should manifest strong
signature for flavor mixing (mostly between channel 4--15)and a relevant
anomaly for eventual CPT violation (MINOS like) written at channel 3--6,whose
statistical weight (mainly at channel 5) might soon confirm or dismiss MINOS
CPT claim. At the flux minimum around channel 6, (a flux suppressed respect the
non oscillated case at least by an order of magnitude) the atmospheric neutrino
paucity offers a better windows to a twenty GeV Neutrino Astronomy. Therefore
by doubling the string array we may foresee a richer rate and a more complete
(zenith and azimuth) atmospheric neutrino distribution and an exciting first
twenty GeV Astronomy.Comment: 8 pages, 8 figure
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
High Energy Neutrino Telescopes
This paper presents a review of the history, motivation and current status of
high energy neutrino telescopes. Many years after these detectors were first
conceived, the operation of kilometer-cubed scale detectors is finally on the
horizon at both the South Pole and in the Mediterranean Sea. These new
detectors will perhaps provide us the first view of high energy astrophysical
objects with a new messenger particle and provide us with our first real
glimpse of the distant universe at energies above those accessible by gamma-ray
instruments. Some of the topics that can be addressed by these new instruments
include the origin of cosmic rays, the nature of dark matter, and the
mechanisms at work in high energy astrophysical objects such as gamma-ray
bursts, active galactic nuclei, pulsar wind nebula and supernova remnants.Comment: 33 pages, 21 figures, accepted for publication in the New Journal of
Physic
All-sky search for time-integrated neutrino emission from astrophysical sources with 7 years of IceCube data
Since the recent detection of an astrophysical flux of high energy neutrinos,
the question of its origin has not yet fully been answered. Much of what is
known about this flux comes from a small event sample of high neutrino purity,
good energy resolution, but large angular uncertainties. In searches for
point-like sources, on the other hand, the best performance is given by using
large statistics and good angular reconstructions. Track-like muon events
produced in neutrino interactions satisfy these requirements. We present here
the results of searches for point-like sources with neutrinos using data
acquired by the IceCube detector over seven years from 2008--2015. The
discovery potential of the analysis in the northern sky is now significantly
below , on average
lower than the sensitivity of the previously published analysis of four
years exposure. No significant clustering of neutrinos above background
expectation was observed, and implications for prominent neutrino source
candidates are discussed.Comment: 19 pages, 17 figures, 3 tables; ; submitted to The Astrophysical
Journa
The contribution of Fermi-2LAC blazars to the diffuse TeV-PeV neutrino flux
The recent discovery of a diffuse cosmic neutrino flux extending up to PeV
energies raises the question of which astrophysical sources generate this
signal. One class of extragalactic sources which may produce such high-energy
neutrinos are blazars. We present a likelihood analysis searching for
cumulative neutrino emission from blazars in the 2nd Fermi-LAT AGN catalogue
(2LAC) using an IceCube neutrino dataset 2009-12 which was optimised for the
detection of individual sources. In contrast to previous searches with IceCube,
the populations investigated contain up to hundreds of sources, the largest one
being the entire blazar sample in the 2LAC catalogue. No significant excess is
observed and upper limits for the cumulative flux from these populations are
obtained. These constrain the maximum contribution of the 2LAC blazars to the
observed astrophysical neutrino flux to be or less between around 10
TeV and 2 PeV, assuming equipartition of flavours at Earth and a single
power-law spectrum with a spectral index of . We can still exclude that
the 2LAC blazars (and sub-populations) emit more than of the observed
neutrinos up to a spectral index as hard as in the same energy range.
Our result takes into account that the neutrino source count distribution is
unknown, and it does not assume strict proportionality of the neutrino flux to
the measured 2LAC -ray signal for each source. Additionally, we
constrain recent models for neutrino emission by blazars.Comment: 18 pages, 22 figure
Calibration and Characterization of the IceCube Photomultiplier Tube
Over 5,000 PMTs are being deployed at the South Pole to compose the IceCube
neutrino observatory. Many are placed deep in the ice to detect Cherenkov light
emitted by the products of high-energy neutrino interactions, and others are
frozen into tanks on the surface to detect particles from atmospheric cosmic
ray showers. IceCube is using the 10-inch diameter R7081-02 made by Hamamatsu
Photonics. This paper describes the laboratory characterization and calibration
of these PMTs before deployment. PMTs were illuminated with pulses ranging from
single photons to saturation level. Parameterizations are given for the single
photoelectron charge spectrum and the saturation behavior. Time resolution,
late pulses and afterpulses are characterized. Because the PMTs are relatively
large, the cathode sensitivity uniformity was measured. The absolute photon
detection efficiency was calibrated using Rayleigh-scattered photons from a
nitrogen laser. Measured characteristics are discussed in the context of their
relevance to IceCube event reconstruction and simulation efforts.Comment: 40 pages, 12 figure
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