187 research outputs found
Searching for eV-scale sterile neutrinos with eight years of atmospheric neutrinos at the IceCube Neutrino Telescope
We report in detail on searches for eV-scale sterile neutrinos, in the context of a 3+1 model, using eight years of data from the IceCube Neutrino Telescope. By analyzing the reconstructed energies and zenith angles of 305,735 atmospheric νμ and ¯νμ events we construct confidence intervals in two analysis spaces: sin2(2θ) vs Δm2¦41 under the conservative assumption θ=0; and sin (2θ) vs sin (2θ) given sufficiently large Δm2¦41 that fast oscillation features are unresolvable. Detailed discussions of the event selection, systematic uncertainties, and fitting procedures are presented. No strong evidence for sterile neutrinos is found, and the best-fit likelihood is consistent with the no sterile neutrino hypothesis with a p value of 8% in the first analysis space and 19% in the second
Search for PeV gamma-ray emission from the southern hemisphere with 5 Yr of data from the IceCube observatory
The measurement of diffuse PeV gamma-ray emission from the Galactic plane would provide information about the energy spectrum and propagation of Galactic cosmic rays, and the detection of a pointlike source of PeV gamma-rays would be strong evidence for a Galactic source capable of accelerating cosmic rays up to at least a few PeV. This paper presents several unbinned maximum-likelihood searches for PeV gamma-rays in the Southern Hemisphere using 5 yr of data from the IceTop air shower surface detector and the in-ice array of the IceCube Observatory. The combination of both detectors takes advantage of the low muon content and deep shower maximum of gamma-ray air showers and provides excellent sensitivity to gamma-rays between similar to 0.6 and 100 PeV. Our measurements of pointlike and diffuse Galactic emission of PeV gamma-rays are consistent with the background, so we constrain the angle-integrated diffuse gamma-ray flux from the Galactic plane at 2 PeV to 2.61 x 10(-19) cm(-2) s(-1) TeV-1 at 90% confidence, assuming an E-3 spectrum, and we estimate 90% upper limits on pointlike emission at 2 PeV between 10(-21) and 10(-20) cm(-2) s(-1) TeV-1 for an E-2 spectrum, depending on decl. Furthermore, we exclude unbroken power-law emission up to 2 PeV for several TeV gamma-ray sources observed by the High Energy Spectroscopic System and calculate upper limits on the energy cutoffs of these sources at 90% confidence. We also find no PeV gamma-rays correlated with neutrinos from IceCube's high-energy starting event sample. These are currently the strongest constraints on PeV gamma-ray emission
eV-Scale Sterile Neutrino Search Using Eight Years of Atmospheric Muon Neutrino Data from the IceCube Neutrino Observatory
The results of a 3+1 sterile neutrino search using eight years of data from the IceCube Neutrino Observatory are presented. A total of 305 735 muon neutrino events are analyzed in reconstructed energy-zenith space to test for signatures of a matter-enhanced oscillation that would occur given a sterile neutrino state with a mass-squared differences between 0.01 and 100 eV. The best-fit point is found to be at sin (2θ)=0.10 and Δm2/41 =4.5 eV, which is consistent with the no sterile neutrino hypothesis with a p value of 8.0%
Searching for eV-scale sterile neutrinos with eight years of atmospheric neutrinos at the IceCube neutrino telescope
We report in detail on searches for eV-scale sterile neutrinos, in the
context of a 3+1 model, using eight years of data from the IceCube neutrino
telescope. By analyzing the reconstructed energies and zenith angles of 305,735
atmospheric and events we construct confidence
intervals in two analysis spaces: vs.
under the conservative assumption ; and
vs. given sufficiently large that
fast oscillation features are unresolvable. Detailed discussions of the event
selection, systematic uncertainties, and fitting procedures are presented. No
strong evidence for sterile neutrinos is found, and the best-fit likelihood is
consistent with the no sterile neutrino hypothesis with a p-value of 8\% in the
first analysis space and 19\% in the second.Comment: This long-form paper is a companion to the letter "An eV-scale
sterile neutrino search using eight years of atmospheric muon neutrino data
from the IceCube Neutrino Observatory". v2: update other experiments contours
on results plo
Characteristics of the diffuse astrophysical electron and tau neutrino flux with six years of IceCube high energy cascade data
We report on the first measurement of the astrophysical neutrino flux using
particle showers (cascades) in IceCube data from 2010 -- 2015. Assuming
standard oscillations, the astrophysical neutrinos in this dedicated cascade
sample are dominated () by electron and tau flavors. The flux,
observed in the sensitive energy range from to
, is consistent with a single power-law model as expected
from Fermi-type acceleration of high energy particles at astrophysical sources.
We find the flux spectral index to be and a flux
normalization for each neutrino flavor of
at , in agreement with IceCube's complementary muon
neutrino results and with all-neutrino flavor fit results. In the measured
energy range we reject spectral indices at
significance level. Due to high neutrino energy resolution and low atmospheric
neutrino backgrounds, this analysis provides the most detailed characterization
of the neutrino flux at energies below compared to
previous IceCube results. Results from fits assuming more complex neutrino flux
models suggest a flux softening at high energies and a flux hardening at low
energies (p-value ). The sizable and smooth flux measured below remains a puzzle. In order to not violate the isotropic
diffuse gamma-ray background as measured by the Fermi-LAT, it suggests the
existence of astrophysical neutrino sources characterized by dense environments
which are opaque to gamma-rays.Comment: 4 figures, 4 tables, includes supplementary materia
IceCube Search for High-Energy Neutrino Emission from TeV Pulsar Wind Nebulae
Pulsar wind nebulae (PWNe) are the main gamma-ray emitters in the Galactic
plane. They are diffuse nebulae that emit nonthermal radiation. Pulsar winds,
relativistic magnetized outflows from the central star, shocked in the ambient
medium produce a multiwavelength emission from the radio through gamma rays.
Although the leptonic scenario is able to explain most PWNe emission, a
hadronic contribution cannot be excluded. A possible hadronic contribution to
the high-energy gamma-ray emission inevitably leads to the production of
neutrinos. Using 9.5 yr of all-sky IceCube data, we report results from a
stacking analysis to search for neutrino emission from 35 PWNe that are
high-energy gamma-ray emitters. In the absence of any significant correlation,
we set upper limits on the total neutrino emission from those PWNe and
constraints on hadronic spectral components.Comment: 11 pages, 2 figures; matches the published version in Ap
IceCube Search for Neutrinos Coincident with Compact Binary Mergers from LIGO-Virgo's First Gravitational-Wave Transient Catalog
Using the IceCube Neutrino Observatory, we search for high-energy neutrino
emission coincident with compact binary mergers observed by the LIGO and Virgo
gravitational wave (GW) detectors during their first and second observing runs.
We present results from two searches targeting emission coincident with the sky
localization of each gravitational wave event within a 1000 second time window
centered around the reported merger time. One search uses a model-independent
unbinned maximum likelihood analysis, which uses neutrino data from IceCube to
search for point-like neutrino sources consistent with the sky localization of
GW events. The other uses the Low-Latency Algorithm for Multi-messenger
Astrophysics, which incorporates astrophysical priors through a Bayesian
framework and includes LIGO-Virgo detector characteristics to determine the
association between the GW source and the neutrinos. No significant neutrino
coincidence is seen by either search during the first two observing runs of the
LIGO-Virgo detectors. We set upper limits on the time-integrated neutrino
emission within the 1000 second window for each of the 11 GW events. These
limits range from 0.02-0.7 . We also set limits on the
total isotropic equivalent energy, , emitted in high-energy
neutrinos by each GW event. These limits range from 1.7 10 -
1.8 10 erg. We conclude with an outlook for LIGO-Virgo
observing run O3, during which both analyses are running in real time
An eV-scale sterile neutrino search using eight years of atmospheric muon neutrino data from the IceCube Neutrino Observatory
The results of a 3+1 sterile neutrino search using eight years of data from
the IceCube Neutrino Observatory are presented. A total of 305,735 muon
neutrino events are analyzed in reconstructed energy-zenith space to test for
signatures of a matter-enhanced oscillation that would occur given a sterile
neutrino state with a mass-squared differences between 0.01\,eV and
100\,eV. The best-fit point is found to be at
and , which is consistent with the no sterile
neutrino hypothesis with a p-value of 8.0\%.Comment: 11 pages, 5 figures. This letter is supported by the long-form paper
"Searching for eV-scale sterile neutrinos with eight years of atmospheric
neutrinos at the IceCube neutrino telescope," also appearing on arXiv.
Digital data release available at:
https://github.com/icecube/HE-Sterile-8year-data-releas
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All-flavor constraints on nonstandard neutrino interactions and generalized matter potential with three years of IceCube DeepCore data
We report constraints on nonstandard neutrino interactions (NSI) from the observation of atmospheric neutrinos with IceCube, limiting all individual coupling strengths from a single dataset. Furthermore, IceCube is the first experiment to constrain flavor-violating and nonuniversal couplings simultaneously. Hypothetical NSI are generically expected to arise due to the exchange of a new heavy mediator particle. Neutrinos propagating in matter scatter off fermions in the forward direction with negligible momentum transfer. Hence the study of the matter effect on neutrinos propagating in the Earth is sensitive to NSI independently of the energy scale of new physics. We present constraints on NSI obtained with an all-flavor event sample of atmospheric neutrinos based on three years of IceCube DeepCore data. The analysis uses neutrinos arriving from all directions, with reconstructed energies between 5.6 GeV and 100 GeV. We report constraints on the individual NSI coupling strengths considered singly, allowing for complex phases in the case of flavor-violating couplings. This demonstrates that IceCube is sensitive to the full NSI flavor structure at a level competitive with limits from the global analysis of all other experiments. In addition, we investigate a generalized matter potential, whose overall scale and flavor structure are also constrained
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