Searcharxiv⌕ Search

arXiv subjects

K. D. Hoffman

Publications and source records attributed to K. D. Hoffman.

25 records · Page 2Linked to original sources
arXiv2010

Measurement of the atmospheric neutrino energy spectrum from 100 GeV to 400 TeV with IceCube

A measurement of the atmospheric muon neutrino energy spectrum from 100 GeV to 400 TeV was performed using a data sample of about 18,000 up-going atmospheric muon neutrino events in IceCube. Boosted decision trees were used for event selection to reject mis-reconstructed atmospheric muons and obtain a sample of up-going muon neutrino events. Background contamination in the final event sample is less than one percent. This is the first measurement of atmospheric neutrinos up to 400 TeV, and is fundamental to understanding the impact of this neutrino background on astrophysical neutrino observations with IceCube. The measured spectrum is consistent with predictions for the atmospheric muon neutrino plus muon antineutrino flux.

astro-ph.HE↗
arXiv2010

Search for a Lorentz-violating sidereal signal with atmospheric neutrinos in IceCube

A search for sidereal modulation in the flux of atmospheric muon neutrinos in IceCube was performed. Such a signal could be an indication of Lorentz-violating physics. Neutrino oscillation models, derivable from extensions to the Standard Model, allow for neutrino oscillations that depend on the neutrino's direction of propagation. No such direction-dependent variation was found. A discrete Fourier transform method was used to constrain the Lorentz and CPT-violating coefficients in one of these models. Due to the unique high energy reach of IceCube, it was possible to improve constraints on certain Lorentz-violating oscillations by three orders of magnitude with respect to limits set by other experiments.

astro-ph.HE↗
arXiv2010

The first search for extremely-high energy cosmogenic neutrinos with the IceCube Neutrino Observatory

We report on the results of the search for extremely-high energy (EHE) neutrinos with energies above $10^7$ GeV obtained with the partially ($\sim$30%) constructed IceCube in 2007. From the absence of signal events in the sample of 242.1 days of effective livetime, we derive a 90% C.L. model independent differential upper limit based on the number of signal events per energy decade at $E^2 ϕ_{ν_e+ν_μ+ν_τ}\simeq 1.4 \times 10^{-6}$ GeV cm$^{-2}$ sec$^{-1}$ sr$^{-1}$ for neutrinos in the energy range from $3\times10^7$ to $3\times10^9$ GeV.

astro-ph.CO↗
arXiv2010

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.

astro-ph.IM↗
arXiv2009

Origin and evolution of cosmic accelerators - the unique discovery potential of an UHE neutrino telescope: Astronomy Decadal Survey (2010-2020) Science White Paper

One of the most tantalizing questions in astronomy and astrophysics, namely the origin and the evolution of the cosmic accelerators that produce the highest energy cosmic rays (UHECR), may be best addressed through the observation of ultra high energy (UHE) cosmogenic neutrinos. Neutrinos travel from their source undeflected by magnetic fields and unimpeded by interactions with the cosmic microwave background. At high energies, neutrinos could be detected in dense, radio frequency (RF) transparent media via the Askaryan effect. The abundant cold ice covering the geographic South Pole, with its exceptional RF clarity, has been host to several pioneering efforts to develop this approach, including RICE and ANITA. Building on the expertise gained in these efforts, and the infrastructure developed in the construction of the IceCube optical Cherenkov observatory, a low-cost array of radio frequency antenna stations could be deployed near the Pole to efficiently detect a significant number of UHE neutrinos with degree scale angular resolution within the next decade. Such an array, if installed in close proximity to IceCube, could allow cross-calibration on a small but invaluable subset of neutrino events detected by both the optical and radio methods. In addition to providing critical information in the identification of the source of UHECRs, such an observatory could also provide a unique probe of long baseline high energy neutrino interactions unattainable in any man-made neutrino beam.

astro-ph.CO↗
arXiv2008

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.

astro-ph↗