Measurement of the ν μ energy spectrum with IceCube-79: IceCube Collaboration

IceCube is a neutrino observatory deployed in the glacial ice at the geographic South Pole. The ν μ 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 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 σ in four adjacent bins for neutrino energies E ν ≥ 177.8 TeV . 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.

Constraints on Ultrahigh-Energy Cosmic-Ray Sources from a Search for Neutrinos above 10 PeV with IceCube

We report constraints on the sources of ultrahigh-energy cosmic rays (UHECRs) above 10^{9}  GeV, based on an analysis of seven years of IceCube data. This analysis efficiently selects very high- energy neutrino-induced events which have deposited energies from 5×10^{5}  GeV to above 10^{11}  GeV. Two neutrino-induced events with an estimated deposited energy of (2.6±0.3)×10^{6}  GeV, the highest neutrino energy observed so far, and (7.7±2.0)×10^{5}  GeV were detected. The atmospheric background-only hypothesis of detecting these events is rejected at 3.6σ. The hypothesis that the observed events are of cosmogenic origin is also rejected at >99% CL because of the limited deposited energy and the nonobservation of events at higher energy, while their observation is consistent with an astrophysical origin. Our limits on cosmogenic neutrino fluxes disfavor the UHECR sources having a cosmological evolution stronger than the star formation rate, e.g., active galactic nuclei and γ-ray bursts, assuming proton-dominated UHECRs. Constraints on UHECR sources including mixed and heavy UHECR compositions are obtained for models of neutrino production within UHECR sources. Our limit disfavors a significant part of parameter space for active galactic nuclei and new-born pulsar models. These limits on the ultrahigh-energy neutrino flux models are the most stringent to date.

Searches for Sterile Neutrinos with the IceCube Detector

The IceCube neutrino telescope at the South Pole has measured the atmospheric muon neutrino spectrum as a function of zenith angle and energy in the approximate 320 GeV to 20 TeV range, to search for the oscillation signatures of light sterile neutrinos. No evidence for anomalous ν_{μ} or ν[over ¯]_{μ} disappearance is observed in either of two independently developed analyses, each using one year of atmospheric neutrino data. New exclusion limits are placed on the parameter space of the 3+1 model, in which muon antineutrinos experience a strong Mikheyev-Smirnov-Wolfenstein-resonant oscillation. The exclusion limits extend to sin^{2}2θ_{24}≤0.02 at Δm^{2}∼0.3  eV^{2} at the 90% confidence level. The allowed region from global analysis of appearance experiments, including LSND and MiniBooNE, is excluded at approximately the 99% confidence level for the global best-fit value of |U_{e4}|^{2}.

Evidence for Astrophysical Muon Neutrinos from the Northern Sky with IceCube

Results from the IceCube Neutrino Observatory have recently provided compelling evidence for the existence of a high energy astrophysical neutrino flux utilizing a dominantly Southern Hemisphere data set consisting primarily of ν(e) and ν(τ) charged-current and neutral-current (cascade) neutrino interactions. In the analysis presented here, a data sample of approximately 35,000 muon neutrinos from the Northern sky is extracted from data taken during 659.5 days of live time recorded between May 2010 and May 2012. While this sample is composed primarily of neutrinos produced by cosmic ray interactions in Earth's atmosphere, the highest energy events are inconsistent with a hypothesis of solely terrestrial origin at 3.7σ significance. These neutrinos can, however, be explained by an astrophysical flux per neutrino flavor at a level of Φ(E(ν))=9.9(-3.4)(+3.9)×10(-19)  GeV(-1) cm(-2) sr(-1) s(-1)(E(ν)/100  TeV(-2), consistent with IceCube's Southern-Hemisphere-dominated result. Additionally, a fit for an astrophysical flux with an arbitrary spectral index is performed. We find a spectral index of 2.2(-0.2)(+0.2), which is also in good agreement with the Southern Hemisphere result.

Flavor Ratio of Astrophysical Neutrinos above 35 TeV in IceCube

A diffuse flux of astrophysical neutrinos above 100 TeV has been observed at the IceCube Neutrino Observatory. Here we extend this analysis to probe the astrophysical flux down to 35 TeV and analyze its flavor composition by classifying events as showers or tracks. Taking advantage of lower atmospheric backgrounds for showerlike events, we obtain a shower-biased sample containing 129 showers and 8 tracks collected in three years from 2010 to 2013. We demonstrate consistency with the (fe:fμ:fτ)⊕≈(1:1:1)⊕ flavor ratio at Earth commonly expected from the averaged oscillations of neutrinos produced by pion decay in distant astrophysical sources. Limits are placed on nonstandard flavor compositions that cannot be produced by averaged neutrino oscillations but could arise in exotic physics scenarios. A maximally tracklike composition of (0:1:0)⊕ is excluded at 3.3σ, and a purely showerlike composition of (1:0:0)⊕ is excluded at 2.3σ.

Development of a general analysis and unfolding scheme and its application to measure the energy spectrum of atmospheric neutrinos with IceCube: IceCube Collaboration

We present the development and application of a generic analysis scheme for the measurement of neutrino spectra with the IceCube detector. This scheme is based on regularized unfolding, preceded by an event selection which uses a Minimum Redundancy Maximum Relevance algorithm to select the relevant variables and a random forest for the classification of events. The analysis has been developed using IceCube data from the 59-string configuration of the detector. 27,771 neutrino candidates were detected in 346 days of livetime. A rejection of 99.9999 % of the atmospheric muon background is achieved. The energy spectrum of the atmospheric neutrino flux is obtained using the TRUEE unfolding program. The unfolded spectrum of atmospheric muon neutrinos covers an energy range from 100 GeV to 1 PeV. Compared to the previous measurement using the detector in the 40-string configuration, the analysis presented here, extends the upper end of the atmospheric neutrino spectrum by more than a factor of two, reaching an energy region that has not been previously accessed by spectral measurements.

Observation of high-energy astrophysical neutrinos in three years of IceCube data

A search for high-energy neutrinos interacting within the IceCube detector between 2010 and 2012 provided the first evidence for a high-energy neutrino flux of extraterrestrial origin. Results from an analysis using the same methods with a third year (2012-2013) of data from the complete IceCube detector are consistent with the previously reported astrophysical flux in the 100 TeV-PeV range at the level of 10(-8)  GeV cm-2 s-1 sr-1 per flavor and reject a purely atmospheric explanation for the combined three-year data at 5.7σ. The data are consistent with expectations for equal fluxes of all three neutrino flavors and with isotropic arrival directions, suggesting either numerous or spatially extended sources. The three-year data set, with a live time of 988 days, contains a total of 37 neutrino candidate events with deposited energies ranging from 30 to 2000 TeV. The 2000-TeV event is the highest-energy neutrino interaction ever observed.

Evidence for high-energy extraterrestrial neutrinos at the IceCube detector

We report on results of an all-sky search for high-energy neutrino events interacting within the IceCube neutrino detector conducted between May 2010 and May 2012. The search follows up on the previous detection of two PeV neutrino events, with improved sensitivity and extended energy coverage down to about 30 TeV. Twenty-six additional events were observed, substantially more than expected from atmospheric backgrounds. Combined, both searches reject a purely atmospheric origin for the 28 events at the 4σ level. These 28 events, which include the highest energy neutrinos ever observed, have flavors, directions, and energies inconsistent with those expected from the atmospheric muon and neutrino backgrounds. These properties are, however, consistent with generic predictions for an additional component of extraterrestrial origin.

Measurement of atmospheric neutrino oscillations with IceCube

We present the first statistically significant detection of neutrino oscillations in the high-energy regime (>20 GeV) from an analysis of IceCube Neutrino Observatory data collected in 2010 and 2011. This measurement is made possible by the low-energy threshold of the DeepCore detector (~20 GeV) and benefits from the use of the IceCube detector as a veto against cosmic-ray-induced muon background. The oscillation signal was detected within a low-energy muon neutrino sample (20-100 GeV) extracted from data collected by DeepCore. A high-energy muon neutrino sample (100 GeV-10 TeV) was extracted from IceCube data to constrain systematic uncertainties. The disappearance of low-energy upward-going muon neutrinos was observed, and the nonoscillation hypothesis is rejected with more than 5σ significance. In a two-neutrino flavor formalism, our data are best described by the atmospheric neutrino oscillation parameters |Δm(32)(2)|=(2.3(-0.5)(+0.6))×10(-3) eV(2) and sin(2)(2θ(23))>0.93, and maximum mixing is favored.

First observation of PeV-energy neutrinos with IceCube

We report on the observation of two neutrino-induced events which have an estimated deposited energy in the IceCube detector of 1.04±0.16 and 1.14±0.17 PeV, respectively, the highest neutrino energies observed so far. These events are consistent with fully contained particle showers induced by neutral-current ν(e,μ,τ) (ν(e,μ,τ)) or charged-current ν(e) (ν(e)) interactions within the IceCube detector. The events were discovered in a search for ultrahigh energy neutrinos using data corresponding to 615.9 days effective live time. The expected number of atmospheric background is 0.082±0.004(stat)(-0.057)(+0.041)(syst). The probability of observing two or more candidate events under the atmospheric background-only hypothesis is 2.9×10(-3) (2.8σ) taking into account the uncertainty on the expected number of background events. These two events could be a first indication of an astrophysical neutrino flux; the moderate significance, however, does not permit a definitive conclusion at this time.

Measurement of the atmospheric νe flux in IceCube

We report the first measurement of the atmospheric electron neutrino flux in the energy range between approximately 80 GeV and 6 TeV, using data recorded during the first year of operation of IceCube's DeepCore low-energy extension. Techniques to identify neutrinos interacting within the DeepCore volume and veto muons originating outside the detector are demonstrated. A sample of 1029 events is observed in 281 days of data, of which 496±66(stat)±88(syst) are estimated to be cascade events, including both electron neutrino and neutral current events. The rest of the sample includes residual backgrounds due to atmospheric muons and charged current interactions of atmospheric muon neutrinos. The flux of the atmospheric electron neutrinos is consistent with models of atmospheric neutrinos in this energy range. This constitutes the first observation of electron neutrinos and neutral current interactions in a very large volume neutrino telescope optimized for the TeV energy range.

Search for dark matter annihilations in the sun with the 79-string IceCube detector

We have performed a search for muon neutrinos from dark matter annihilation in the center of the Sun with the 79-string configuration of the IceCube neutrino telescope. For the first time, the DeepCore subarray is included in the analysis, lowering the energy threshold and extending the search to the austral summer. The 317 days of data collected between June 2010 and May 2011 are consistent with the expected background from atmospheric muons and neutrinos. Upper limits are set on the dark matter annihilation rate, with conversions to limits on spin-dependent and spin-independent scattering cross sections of weakly interacting massive particles (WIMPs) on protons, for WIMP masses in the range 20-5000  GeV/c2. These are the most stringent spin-dependent WIMP-proton cross section limits to date above 35  GeV/c2 for most WIMP models.

Limits on neutrino emission from gamma-ray bursts with the 40 string IceCube detector

IceCube has become the first neutrino telescope with a sensitivity below the TeV neutrino flux predicted from gamma-ray bursts if gamma-ray bursts are responsible for the observed cosmic-ray flux above 10(18)  eV. Two separate analyses using the half-complete IceCube detector, one a dedicated search for neutrinos from pγ interactions in the prompt phase of the gamma-ray burst fireball and the other a generic search for any neutrino emission from these sources over a wide range of energies and emission times, produced no evidence for neutrino emission, excluding prevailing models at 90% confidence.

Enterobiasis: a histopathological study of 259 patients

Enterobius worms or their eggs, or both, are present in preserved tissue sections or tissue specimens of 259 patients whose medical records are on file at the Armed Forces Institute of Pathology, Washington D.C., U.S.A. The most common site of infection (86.5%) was found to be the lumen of the appendix, where the worms provoke no reaction. Of the 259 patients 11 (4.2%) had worms and/or eggs in granulomas of the abdominal and pelvic peritoneum, and an equal number had granulomas on the peritoneum of the salphinx or on the surface of the ovary. There were also ectopic worms and/or eggs in granulomas on the peritoneum of the small and large intestines (2.7%). These Enterobius granulomas form around degenerating adult worms, around discrete eggs, around clusters of eggs, and, we believe, also around the tracks of migrating worms. Three patients (1.2%) had worms in perianal abscesses. A necrotic granuloma, removed from the lung of one patient, surrounded a degenerating adult worm. This suggests that the worm, carried to the lung as an embolus, impacted in a pulmonary arteriole. A stool specimen of one patient contains eggs of Enterobius, and that of another patient contains an adult Enterobius. This is the largest recorded histopathological study of enterobiasis in man.

Cysticercosis. A modern day plague

The authors describe the magnitude of the cysticercosis problem and describe the organism, the clinical features of the disease, the propensity of the organism for development in the central nervous system, pathologic considerations, clinical diagnosis, and treatment.

Secretory/excretory antigens produced by tetrathyridia of Mesocestoides corti defined by SDS--PAGE and HPLC

Antigens derived from culture medium in which metacestodes of Mesocestoides corti Hoeppli, 1925, had been maintained were studied by sodium-dodecyl-sulfate--polyacrylamide gel electrophoresis (SDS--PAGE) and high performance liquid chromatography (HPLC). By SDS--PAGE a minimum of 18 Coomassie-staining bands were discerned, of which 4 major bands and 4 major peaks by HPLC of similar molecular weights were observed. The HPLC eluate peaks were analyzed for antigenic activity in vitro by double diffusion in two dimensions, and in vivo in a rabbit. The rabbit had been artificially sensitized with a dialyzable leukocyte extract, showing transfer-factor-like activity, from peritoneal exudate cells removed from mice infected with tetrathyridia. All of the HPLC fractions reacted with rabbit antibody prepared against secretory/excretory antigens, but the sensitized rabbit responded only to two fractions. It is now possible by HPLC to fractionate complex antigens without denaturing them and to elucidate further the role they play during infection.

Diagnostic clinical parasitology: IV. Identification of the blood parasites?

This is the fourth article in a series of articles entitled "Diagnostic Clinical Parasitology" and contains information on the recovery and identification of human blood parasites. The organisms covered include those that cause the diseases malaria, babesiosis, leishmaniasis, and trypanosomiasis. Some of the filarial worms, which can be considered "blood parasites," have been discussed in the third article in the series, "Identification of the Helminths." Although some of these organisms may rarely be encountered in the laboratory in clinical specimens, they will probably have to be identified in proficiency testing specimens, some of which may not always be representative of patient clinical material. The differences between potential organism recovery from patients coming from endemic areas and from those individuals who become infected with no prior exposure to the organism will also be emphasized. Often, for a number of different reasons, organism recovery and subsequent identification may be more difficult than the textbook imply. It is very important for the technologist to recognize this fact, particularly when dealing with a possibly fatal infection, ie, Plasmodium falciparum.

Changes in the tegumental surface of Schistosoma haematobium during development in the mammalian host

The development of surface of Schistosoma haematobium in the mammalian host was studied by scanning electron microscopy, beginning with lung stages obtained at 7 days, and at various intervals thereafter to completion of development. The major changes observed were similar to those previously seen in Schistosoma mansoni.

Diagnostic clinical parasitology: II. Identification of the intestinal protozoa

This article (the second in a series of four papers on clinical diagnostic parasitology) presents information on the diagnostic morphology of the protozoa which infect humans. The description of morphological characteristics includes information on atypical morphology as well as the classic descriptions. Because these organisms are the most difficult to identify, extensive detail is included to illustrate the morphological variability.

Diagnostic clinical parasitology: I. Proper specimen collection and processing

This article (first of a series of four papers on diagnostic clinical parasitology) presents various collection methods and diagnostic procedures which are available for laboratory diagnosis of human parasitic infections. The information presented includes the pros and cons of each method discussed. When a laboratory selects various procedures, this decision should be based on a thorough understanding of the value and limitations of each technique selected. The topics to be included in the next three presentations include: protozoa, helminths, and blood parasites.

Circulating antigens in infections of mice by tetrathyridia of Mesocestoides corti Hoeppli, 1925

Two circulating antigens were detected in the serum of ICR/Timco female mice infected intraperitonealy with tetrathyridia of the cestode Mesocestoides corti Hoeppli, 1925. One circulating antigen appeared by day 2 postinfection (p.i.) and remained in all mice until at least 90 days p.i. A second antigen appeared in the serum on day 14 p.i. and disappeared from all mice by day 28 p.i. Infected mouse serum also contained antibodies against one secretory/excretory antigen and two antigens in crude homogenate, as judged by double diffusion in two dimensions (Ouchterlony). Immune deposits were observed in the kidney tissue of Rockland mice by transmission electron microscopy, and their identity as products of tetrathyridia was confirmed by immunofluorescence. Further studies showed that the main antibody subclass associated with the mesangial immune deposits was 7S gamma l, and that other subclasses of IgG and IgM were not involved. Antigen was found in the proximal renal tubules of infected mice, as demonstrated by fluorescein-labeled IgG fraction of rabbit antitetrathyridia secretory/excretory antigen antisera. The presence of tetrathyridia antigen in the urine of infected mice was confirmed using the Ouchterlony technique.

Intestinal parasites in Los Angeles, California

Because of an apparent increase in the number of parasitic infections in Los Angeles, California, a six-month retrospective analysis of data obtained from patient stool examinations for parasitic infections in out-patient populations from two county health facilities in Los Angeles County was compared with a survey published in 1936 and 1960. A significant increase in the incidence of pathogenic intestinal protozoal parasites was found to occur in the areas surveyed. Giardia lamblia and nonpathogenic Endolimax nana occurred with the greatest frequency.

Fine structure of the tegument of Mesocestoides tetrathyridia by scanning and transmission electron microscopy

The tegumental surface of tetrathyridial stages of the tapeworm, Mesocestoides corti, was studied by scanning and transmission electron microscopy. Two structural types of microvilli were observed--blade-shaped or conical ones, and elongated, slender microvilli. The distribution and relative frequency of the two types of microvilli differs in different areas of the body surface. Host peritoneal cells were observed attached to the blade-shaped microvilli by slender cytoplasmic projections.

Schistosoma mekongi sp. n. from man and animals, compared with four geographic strains of Schistosoma japonicum

Schistosoma mekongi sp. n. is described from man and animals in Cambodia. It is compared to 4 geographic strains of Schistosoma japonicum. It differs from S. japonicum in the size of embryonated eggs, in the length of the prepatent peroid in the mammalian host, and in its utilization of a different snail host. The relative usefulness of conventional morphologic criteria in the differentiation of Asian schistosomes is discussed.

Immunoglobulins on the surfaces of tetrathyridia of Mesocestoides corti Hoeppli 1925 (Cestoda), from laboratory infections of ICR mice

7Sgamma2b antibody was detected, by fluorescein labeled antibodies, on the body surfaces and wall of excretory bladder of tetrathyridia of M. corti removed from the peritoneums of 5--24-week laboratory infections of ICR/TIMCO mice. 7Sgamma1, 7Sgamma2a, 7Sgamma3, IgM, IgA, and C3 were not found by use of the same techniques. Tetrathyridia maintained in culture medium to which pooled normal mouse, infected mouse, and horse (control) serums containing all known classes and subclasses of immunoglobulins had been added showed only mouse 7Sgamma2b on their surfaces and wall of the excretory bladder, and then only when incubated in pooled serum from infected mice. No other mouse immunoglobulin classes or subclasses were found attached to the worms, nor was any reaction obtained from tetrathyridia incubated in culture medium alone, normal mouse serum, or horse serum. This suggests a highly selective nonspecific absorption of 7Sgamma2b, or more likely demonstrates the specificity of the antibody for the parasite surfaces and wall of the excretory bladder. The possibility that 7Sgamma2b may be acting in an enhanceing mode is discussed.

Changes in tegumental surface during development of Schistosoma mansoni

The tegumental surface of immature Schistosoma mansoni was studied with the scanning electron microscope. The surfaces of immature males and females bear no resemblance to that of adult worms and are characterized by having many tegumental folds. The tegumental surfaces of immature males and females are similar, and the dorsal and ventral surfaces of the male are similar before formation of the gynecophoral canal. Transition of the tegumental surface from the juvenile to the adult form begins after worms are in copula and have grown to several millimeters in length.

Synergistic growth promoting action of L-cysteine and nitrogen upon Hymenolepis diminuta cysticercoids in vitro

Development in vitro of cysticercoids of the cestode Hymenolepis diminuta in the presence of L-cysteine proceeded twice as rapidly under 100% nitrogen as it did with air as the gas phase. No growth was obtained with the following: D-cysteine, L-cysteine methyl ester, S-aminoethyl cysteine, L-cystine, glutathione (reduced), L-methionine, D-pantothenic acid, taurine, or thioglycolic acid; limited growth only was obtained with ascorbic acid and dithiothreitol. Homocysteine or coenzyme A was as effective as L-cysteine in stimulating the complete development of oncospheres to cysticercoids. Experiments with 14C-L-cysteine indicated that L-cysteine was perhaps incorporated into the organisms.

Strongyloides fulleborni-like infections in man in Papua New Guinea

During the course of a survey of intestinal parasites among the inhabitants of villages along the Fly River in the Kiunga region of Papua New Guinea, eggs of a Strongyloides species were found in the feces of several persons. In subsequent studies, 93 (17.8%) of 520 persons examined from five villages were found to be infected with this parasite. The examination of parasitic and free-living stages of the worm revealed that it is very similar to S. fulleborni, a parasite of monkeys, baboons and apes in Africa and Asia, although a definitive identification could not be made with the material available. Since non-human primates have apparently never inhabited New Guinea, the origin of these S. fulleborni-like infections is unknown.