19 research outputs found
Results from Seven Years of AMANDA-II
AMANDA is a first-generation high energy neutrino telescope, which has taken
data at the South Pole in its final configuration since 2000. Results from
seven years of operation are presented here, including observation of the
atmopheric neutrino flux and searches for astrophysical neutrinos from cosmic
ray accelerators, gamma ray bursts, and dark matter annihilations. In 2007,
AMANDA was incorporated into the IceCube neutrino telescope, where its higher
density of instrumentation improves the low energy response. In the near
future, AMANDA will be replaced by the IceCube Deep Core, a purpose-built low
energy extension of IceCube.Comment: Presented at Neutrino 2008, Christchurch, New Zealan
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Multi-year search for a diffuse flxu of muon neutrinos with AMANDA-II
A search for TeV-PeV muon neutrinos from unresolved sources was performed on AMANDA-II data collected between 2000 and 2003 with an equivalent livetime of 807 days. This diffuse analysis sought to find an extraterrestrial neutrino flux from sources with non-thermal components. The signal is expected to have a harder spectrum than the atmospheric muon and neutrino backgrounds. Since no excess of events was seen in the data over the expected background, an upper limit of E{sup 2}{Phi}{sub 90%C.L.} < 7.4 x 10{sup -8} GeV cm{sup -2} s{sup -1} sr{sup -1} is placed on the diffuse flux of muon neutrinos with a {Phi} {proportional_to} E{sup -2} spectrum in the energy range 16 TeV to 2.5 PeV. This is currently the most sensitive {Phi} {proportional_to} E{sup -2} diffuse astrophysical neutrino limit. We also set upper limits for astrophysical and prompt neutrino models, all of which have spectra different than {Phi} {proportional_to} E{sup -2}
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The Search for Muon Neutrinos from Northern HemisphereGamma-Ray Bursts with AMANDA
We present the results of the analysis of neutrino observations by the Antarctic Muon and Neutrino Detector Array (AMANDA) correlated with photon observations of more than 400 gamma-ray bursts (GRBs) in the Northern Hemisphere from 1997 to 2003. During this time period, AMANDA's effective collection area for muon neutrinos was larger than that of any other existing detector. Based on our observations of zero neutrinos during and immediately prior to the GRBs in the dataset, we set the most stringent upper limit on muon neutrino emission correlated with gamma-ray bursts. Assuming a Waxman-Bahcall spectrum and incorporating all systematic uncertainties, our flux upper limit has a normalization at 1 PeV of E{sup 2}{Phi}{sub {nu}} {le} 6.0 x 10{sup -9} GeV cm{sup -2}s{sup -1}sr{sup -1}, with 90% of the events expected within the energy range of {approx}10 TeV to {approx}3 PeV. The impact of this limit on several theoretical models of GRBs is discussed, as well as the future potential for detection of GRBs by next generation neutrino telescopes. Finally, we briefly describe several modifications to this analysis in order to apply it to other types of transient point sources
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Detection of Atmospheric Muon Neutrinoswith the IceCube 9-String Detector
The IceCube neutrino detector is a cubic kilometer TeV to PeV neutrino detector under construction at the geographic South Pole. The dominant population of neutrinos detected in IceCube is due to meson decay in cosmic-ray air showers. These atmospheric neutrinos are relatively well understood and serve as a calibration and verification tool for the new detector. In 2006, the detector was approximately 10% completed, and we report on data acquired from the detector in this configuration. We observe an atmospheric neutrino signal consistent with expectations, demonstrating that the IceCube detector is capable of identifying neutrino events. In the first 137.4 days of livetime, 234 neutrino candidates were selected with an expectation of 211 {+-} 76.1(syst.) {+-} 14.5(stat.) events from atmospheric neutrinos
Dark Matter in split extended supersymmetry
We consider the split extended (N=2) supersymmetry scenario recently proposed
by Antoniadis et al. [hep-ph/0507192] as a realistic low energy framework
arising from intersecting brane models. While all scalar superpartners and
charged gauginos are naturally at a heavy scale, the model low energy spectrum
contains a Higgsino-like chargino and a neutralino sector made out of two
Higgsino and two Bino states. We show that the lightest neutralino is a viable
dark matter candidate, finding regions in the parameter space where its thermal
relic abundance matches the latest determination of the density of matter in
the
Universe by WMAP. We also discuss dark matter detection strategies within
this model: we point out that current data on cosmic-ray antimatter already
place significant constraints on the model, while direct detection is the most
promising technique for the future. Analogies and differences with respect to
the standard split
SUSY scenario based on the MSSM are illustrated.Comment: 14 pages, references added, typos corrected, matches with the
published versio
TeV Particle Astrophysics II: Summary comments
A unifying theme of this conference was the use of different approaches to
understand astrophysical sources of energetic particles in the TeV range and
above. In this summary I review how gamma-ray astronomy, neutrino astronomy and
(to some extent) gravitational wave astronomy provide complementary avenues to
understanding the origin and role of high-energy particles in energetic
astrophysical sources.Comment: 6 pages, 4 figures; Conference summary talk for "TeV Particle
Astrophysics II" at University of Wisconsin, Madison, 28-31 August 200
Increasing the Neutralino Relic Abundance with Slepton Coannihilations: Consequences for Indirect Dark Matter Detection
We point out that if the lightest supersymmetric particle (LSP) is a
Higgsino- or Wino-like neutralino, the net effect of coannihilations with
sleptons is to increase the relic abundance, rather than producing the usual
suppression, which takes place if the LSP is Bino-like. The reason for the
enhancement lies in the effective thermally averaged cross section at
freeze-out: sleptons annihilate (and co-annihilate) less efficiently than the
neutralino(s)-chargino system, therefore slepton coannihilations effectively
act as parasite degrees of freedom at freeze-out. Henceforth, the thermal relic
abundance of LSP's corresponds to the cold Dark Matter abundance for smaller
values of the LSP mass, and larger values of the neutralino pair annihilation
cross section. In turn, at a given thermal neutralino relic abundance, this
implies larger indirect detection rates, as a result of an increase in the
fluxes of antimatter, gamma rays and neutrinos from the Sun orginating from
neutralino pair annihilations.Comment: 16 pages, 6 figures, references added, typos corrected, matches with
the published versio
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
Probing new physics with long-lived charged particles produced by atmospheric and astrophysical neutrinos
As suggested by some extensions of the Standard Model of particle physics,
dark matter may be a super-weakly interacting lightest stable particle, while
the next-to-lightest particle (NLP) is charged and meta-stable. One could test
such a possibility with neutrino telescopes, by detecting the charged NLPs
produced in high-energy neutrino collisions with Earth matter. We study the
production of charged NLPs by both atmospheric and astrophysical neutrinos;
only the latter, which is largely uncertain and has not been detected yet, was
the focus of previous studies. We compute the resulting fluxes of the charged
NLPs, compare those of different origins, and analyze the dependence on the
underlying particle physics setup. We point out that even if the astrophysical
neutrino flux is very small, atmospheric neutrinos, especially those from the
prompt decay of charmed mesons, may provide a detectable flux of NLP pairs at
neutrino telescopes such as IceCube. We also comment on the flux of charged
NLPs expected from proton-nucleon collisions, and show that, for theoretically
motivated and phenomenologically viable models, it is typically sub-dominant
and below detectable rates.Comment: 27 pages, 6 figures; accepted for publication in JCA