With the observation of high-energy astrophysical neutrinos by the IceCube Neutrino Observatory, interest has risen in models of PeV-mass decaying dark matter particles to explain the observed flux. ...We present two dedicated experimental analyses to test this hypothesis. One analysis uses 6 years of IceCube data focusing on muon neutrino 'track' events from the Northern Hemisphere, while the second analysis uses 2 years of 'cascade' events from the full sky. Known background components and the hypothetical flux from unstable dark matter are fitted to the experimental data. Since no significant excess is observed in either analysis, lower limits on the lifetime of dark matter particles are derived: we obtain the strongest constraint to date, excluding lifetimes shorter than Formula omitted at 90% CL for dark matter masses above Formula omitted.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The mass composition of high energy cosmic rays depends on their production, acceleration, and propagation. The study of cosmic ray composition can therefore reveal hints of the origin of these ...particles. At the South Pole, the IceCube Neutrino Observatory is capable of measuring two components of cosmic ray air showers in coincidence: the electromagnetic component at high altitude (2835 m) using the IceTop surface array, and the muonic component above similar to 1 TeV using the IceCube array. This unique detector arrangement provides an opportunity for precision measurements of the cosmic ray energy spectrum and composition in the region of the knee and beyond. We present the results of a neural network analysis technique to study the cosmic ray composition and the energy spectrum from 1 PeV to 30 PeV using data recorded using the 40-string/40-station configuration of the IceCube Neutrino Observatory.
Background:
Track & field has more combined participants compared to any other high school sport in the United States. Hurdling is a track event that is unique due to a combination of running and ...jumping over an apparatus. As a result, this puts athletes at risk for various musculoskeletal injuries. However, there has been a paucity of studies describing the epidemiology of pediatric hurdle injuries
Purpose:
To examine hurdle-related injury types, body locations, injury mechanisms, and injury settings in children and adolescents.
Methods:
This was a retrospective review of data that was extracted from the National Electronic Injury Surveillance System (NEISS), which represents emergency room visits. Injury data involving hurdle injuries was searched during a 10-year period (2008-2017) involving patients 18 and under. Injuries were then classified based upon injury type, body locations involved, injury mechanisms, and injury settings. Descriptive statistics were used including mean ± standard deviation and frequency (N) was expressed as percentages (%).
Results:
A total of 749 hurdle related injuries were found from 333 males (44.5%) and 416 females (55.5%). Their mean ages were 14.0±2.2 years. The top 3 commonly recorded injury types were traumatic fracture (N=218, 29.1%), joint sprain (N=191, 25.5%), and contusion/hematoma/bruise (N=78, 10.4%). The overall top 3 injured body locations were ankle (N=140, 18.7%), knee (N=120, 16.0%), and wrist (N=69, 9.2%). Most injury mechanisms were trips, falls, and landings involving the hurdle (N=594, 79.0%). The rest of the mechanisms included ground involvement only (N=47, 6.3%) and other equipment (N=7, 0.9%). Finally, injury settings consisted of track & field practices (N=469, 62.6%), track & field meets (N=96, 12.8%), and other settings including gym, physical education class, recess, school activities, and camps (N=49, 6.5%).
Conclusion:
In pediatric hurdle athletes, most injuries seen in the emergency room are due to involvement of the hurdle and most occur during track practices. Although most injuries occur in the lower extremity, upper extremity injuries are also common. This information could be helpful in playing a role in targeted event-specific injury prevention initiatives.
In this paper we describe the first results of IceAct, a compact imaging air-Cherenkov telescope operating in coincidence with the IceCube Neutrino Observatory (IceCube) at the geographic South Pole. ...An array of IceAct telescopes (referred to as the IceAct project) is under consideration as part of the IceCube-Gen2 extension to IceCube. Surface detectors in general will be a powerful tool in IceCube-Gen2 for distinguishing astrophysical neutrinos from the dominant backgrounds of cosmic-ray induced atmospheric muons and neutrinos: the IceTop array is already in place as part of IceCube, but has a high energy threshold. Although the duty cycle will be lower for the IceAct telescopes than the present IceTop tanks, the IceAct telescopes may prove to be more effective at lowering the detection threshold for air showers. Additionally, small imaging air-Cherenkov telescopes in combination with IceTop, the deep IceCube detector or other future detector systems might improve measurements of the composition of the cosmic ray energy spectrum. In this paper we present measurements of a first 7-pixel imaging air Cherenkov telescope demonstrator, proving the capability of this technology to measure air showers at the South Pole in coincidence with IceTop and the deep IceCube detector.
Abstract IceCube is a neutrino observatory deployed in the glacial ice at the geographic South Pole. The $$\nu _\mu $$ νμ energy unfolding described in this paper is based on data taken with IceCube ...in its 79-string configuration. A sample of muon neutrino charged-current interactions with a purity of 99.5% was selected by means of a multivariate classification process based on machine learning. The subsequent unfolding was performed using the software Truee. The resulting spectrum covers an E$$_\nu $$ ν -range of more than four orders of magnitude from 125 GeV to 3.2 PeV. Compared to the Honda atmospheric neutrino flux model, the energy spectrum shows an excess of more than $$1.9\,\sigma $$ 1.9σ in four adjacent bins for neutrino energies $$E_\nu \ge 177.8\,\text {TeV}$$ Eν≥177.8TeV . The obtained spectrum is fully compatible with previous measurements of the atmospheric neutrino flux and recent IceCube measurements of a flux of high-energy astrophysical neutrinos.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The IceCube Neutrino Observatory was designed primarily to search for high-energy (TeV-PeV) neutrinos produced in distant astrophysical objects. A search for > ~ 100 TeV neutrinos interacting inside ...the instrumented volume has recently provided evidence for an isotropic flux of such neutrinos. At lower energies, IceCube collects large numbers of neutrinos from the weak decays of mesons in cosmic-ray air showers. Here we present the results of a search for neutrino interactions inside IceCube's instrumented volume between 1 TeV and 1 PeV in 641 days of data taken from 2010-2012, lowering the energy threshold for neutrinos from the southern sky below 10 TeV for the first time, far below the threshold of the previous high-energy analysis. Astrophysical neutrinos remain the dominant component in the southern sky down to a deposited energy of 10 TeV. From these data we derive new constraints on the diffuse astrophysical neutrino spectrum, (ProQuest: Formulae and/or non-USASCII text omitted), as well as the strongest upper limit yet on the flux of neutrinos from charmed-meson decay in the atmosphere, 1.52 times the benchmark theoretical prediction used in previous IceCube results at 90% confidence.
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