Many Galactic sources of gamma rays, such as supernova remnants, are expected to produce neutrinos with a typical energy cutoff well below 100 TeV. For the IceCube Neutrino Observatory located at the ...South Pole, the southern sky, containing the inner part of the Galactic plane and the Galactic Center, is a particularly challenging region at these energies, because of the large background of atmospheric muons. In this paper, we present recent advancements in data selection strategies for track-like muon neutrino events with energies below 100 TeV from the southern sky. The strategies utilize the outer detector regions as veto and features of the signal pattern to reduce the background of atmospheric muons to a level which, for the first time, allows IceCube searching for point-like sources of neutrinos in the southern sky at energies between 100 GeV and several TeV in the muon neutrino charged current channel. No significant clustering of neutrinos above background expectation was observed in four years of data recorded with the completed IceCube detector. Upper limits on the neutrino flux for a number of spectral hypotheses are reported for a list of astrophysical objects in the southern hemisphere.
As the feature sizes of semiconductor devices continue to shrink, there is an increasing interest in thin film imaging approaches such as silicon-based bilayer resists. We have developed such a ...resist based on a copolymer of 4-hydroxystyrene with a silicon-containing monomer, which functions simultaneously as the acid-sensitive component and a source of O2 etch resistance. In an attempt to understand the reactions that occur in the photoresist film, the acidolysis reactions of the 2-tris(trimethylsilyl)silylethyl moiety have been studied in solution. Acid-catalyzed cleavage of the model 2-trimethylsilylethyl acetate in solution proceeds via a nucleophilic attack on the silicon atom of the protonated acetate. Protonation of 2-tris(trimethylsilyl)silylethyl acetate is postulated to lead to a bridged siliconium cation, which reacts with nucleophiles along three pathways and yields products in which a nucleophile is attached to a silicon atom. This mechanism is consistent with the silylation of phenolic hydroxyl groups in the photoresist film consisting of a copolymer of 4-hydroxystyrene with 2-tris(trimethylsilyl)silylethyl methacrylate, observed during photolithographic processing.
The IceCube project has transformed 1km3 of deep natural Antarctic ice into a Cherenkov detector. Muon neutrinos are detected and their direction is inferred by mapping the light produced by the ...secondary muon track inside the volume instrumented with photomultipliers. Reconstructing the muon track from the observed light is challenging due to noise, light scattering in the ice medium, and the possibility of simultaneously having multiple muons inside the detector, resulting from the large flux of cosmic ray muons.
This paper describes work on two problems: (1) the track reconstruction problem, in which, given a set of observations, the goal is to recover the track of a muon; and (2) the coincident event problem, which is to determine how many muons are active in the detector during a time window. Rather than solving these problems by developing more complex physical models that are applied at later stages of the analysis, our approach is to augment the detector's early reconstruction with data filters and robust statistical techniques. These can be implemented at the level of on-line reconstruction and, therefore, improve all subsequent reconstructions. Using the metric of median angular resolution, a standard metric for track reconstruction, we improve the accuracy in the initial reconstruction direction by 13%. We also present improvements in measuring the number of muons in coincident events: we can accurately determine the number of muons 98% of the time.
In the analyses, published in Ref. 1, the exclusion limits are calculated in dependence of the mean free path of the magnetic monopole - nucleon catalysis interaction.
ABSTRACT We present the results of a search for astrophysical sources of brief transient neutrino emission using IceCube and DeepCore data acquired between 2012 May 15 and 2013 April 30. While the ...search methods employed in this analysis are similar to those used in previous IceCube point source searches, the data set being examined consists of a sample of predominantly sub-TeV muon-neutrinos from the Northern Sky (−5 ) obtained through a novel event selection method. This search represents a first attempt by IceCube to identify astrophysical neutrino sources in this relatively unexplored energy range. The reconstructed direction and time of arrival of neutrino events are used to search for any significant self-correlation in the data set. The data revealed no significant source of transient neutrino emission. This result has been used to construct limits at timescales ranging from roughly 1 s to 10 days for generic soft-spectra transients. We also present limits on a specific model of neutrino emission from soft jets in core-collapse supernovae.
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.
Using the South Pole Acoustic Test Setup (SPATS) and a retrievable transmitter deployed in holes drilled for the IceCube experiment, we have measured the attenuation of acoustic signals by South Pole ...ice at depths between 190
m and 500
m. Three data sets, using different acoustic sources, have been analyzed and give consistent results. The method with the smallest systematic uncertainties yields an amplitude attenuation coefficient
α
=
3.20
±
0.57
km
−1 between 10 and 30
kHz, considerably larger than previous theoretical estimates. Expressed as an attenuation length, the analyses give a consistent result for
λ
≡
1/
α of ∼300
m with 20% uncertainty. No significant depth or frequency dependence has been found.
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