152 research outputs found
Identification and Characterization of Ixodes scapularis Antigens That Elicit Tick Immunity Using Yeast Surface Display
Repeated exposure of rabbits and other animals to ticks results in acquired resistance or immunity to subsequent tick bites and is partially elicited by antibodies directed against tick antigens. In this study we demonstrate the utility of a yeast surface display approach to identify tick salivary antigens that react with tick-immune serum. We constructed an Ixodes scapularis nymphal salivary gland yeast surface display library and screened the library with nymph-immune rabbit sera and identified five salivary antigens. Four of these proteins, designated P8, P19, P23 and P32, had a predicted signal sequence. We generated recombinant (r) P8, P19 and P23 in a Drosophila expression system for functional and immunization studies. rP8 showed anti-complement activity and rP23 demonstrated anti-coagulant activity. Ixodes scapularis feeding was significantly impaired when nymphs were fed on rabbits immunized with a cocktail of rP8, rP19 and rP23, a hall mark of tick-immunity. These studies also suggest that these antigens may serve as potential vaccine candidates to thwart tick feeding
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
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
A muon-track reconstruction exploiting stochastic losses for large-scale Cherenkov detectors
IceCube is a cubic-kilometer Cherenkov telescope operating at the South Pole.
The main goal of IceCube is the detection of astrophysical neutrinos and the
identification of their sources. High-energy muon neutrinos are observed via
the secondary muons produced in charge current interactions with nuclei in the
ice. Currently, the best performing muon track directional reconstruction is
based on a maximum likelihood method using the arrival time distribution of
Cherenkov photons registered by the experiment's photomultipliers. A known
systematic shortcoming of the prevailing method is to assume a continuous
energy loss along the muon track. However at energies TeV the light yield
from muons is dominated by stochastic showers. This paper discusses a
generalized ansatz where the expected arrival time distribution is parametrized
by a stochastic muon energy loss pattern. This more realistic parametrization
of the loss profile leads to an improvement of the muon angular resolution of
up to for through-going tracks and up to a factor 2 for starting tracks
over existing algorithms. Additionally, the procedure to estimate the
directional reconstruction uncertainty has been improved to be more robust
against numerical errors
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
A search for time-dependent astrophysical neutrino emission with IceCube data from 2012 to 2017
High-energy neutrinos are unique messengers of the high-energy universe,
tracing the processes of cosmic-ray acceleration. This paper presents analyses
focusing on time-dependent neutrino point-source searches. A scan of the whole
sky, making no prior assumption about source candidates, is performed, looking
for a space and time clustering of high-energy neutrinos in data collected by
the IceCube Neutrino Observatory between 2012 and 2017. No statistically
significant evidence for a time-dependent neutrino signal is found with this
search during this period since all results are consistent with the background
expectation. Within this study period, the blazar 3C 279, showed strong
variability, inducing a very prominent gamma-ray flare observed in 2015 June.
This event motivated a dedicated study of the blazar, which consists of
searching for a time-dependent neutrino signal correlated with the gamma-ray
emission. No evidence for a time-dependent signal is found. Hence, an upper
limit on the neutrino fluence is derived, allowing us to constrain a hadronic
emission model
LeptonInjector and LeptonWeighter: A neutrino event generator and weighter for neutrino observatories
We present a high-energy neutrino event generator, called LeptonInjector,
alongside an event weighter, called LeptonWeighter. Both are designed for
large-volume Cherenkov neutrino telescopes such as IceCube. The neutrino event
generator allows for quick and flexible simulation of neutrino events within
and around the detector volume, and implements the leading Standard Model
neutrino interaction processes relevant for neutrino observatories:
neutrino-nucleon deep-inelastic scattering and neutrino-electron annihilation.
In this paper, we discuss the event generation algorithm, the weighting
algorithm, and the main functions of the publicly available code, with
examples.Comment: 28 pages, 10 figures, 3 table
Measurement of Astrophysical Tau Neutrinos in IceCube's High-Energy Starting Events
We present the results of a search for astrophysical tau neutrinos in 7.5
years of IceCube's high-energy starting event data. At high energies, two
energy depositions stemming from the tau neutrino charged-current interaction
and subsequent tau lepton decay may be resolved. We report the first detection
of two such events, with probabilities of and of being
produced by astrophysical tau neutrinos. The resultant astrophysical neutrino
flavor measurement is consistent with expectations, disfavoring a
no-astrophysical tau neutrino flux scenario with 2.8 significance.Comment: This article is supported by a long-form paper that discusses the
high-energy starting event selection titled: "The IceCube high-energy
starting event sample: Description and flux characterization with 7.5 years
of data.
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
- …