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Hulth, Per Olof
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Publications (10 of 95) Show all publications
Ahrens, M., Bohm, C., Dumm, J. P., Finley, C., Flis, S., Hulth, P. O., . . . Zoll, M. (2017). The IceCube Neutrino Observatory: instrumentation and online systems. Journal of Instrumentation, 12, Article ID P03012.
Open this publication in new window or tab >>The IceCube Neutrino Observatory: instrumentation and online systems
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2017 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 12, article id P03012Article in journal (Refereed) Published
Abstract [en]

The IceCube Neutrino Observatory is a cubic-kilometer-scale high-energy neutrino detector built into the ice at the South Pole. Construction of IceCube, the largest neutrino detector built to date, was completed in 2011 and enabled the discovery of high-energy astrophysical neutrinos. We describe here the design, production, and calibration of the IceCube digital optical module (DOM), the cable systems, computing hardware, and our methodology for drilling and deployment. We also describe the online triggering and data filtering systems that select candidate neutrino and cosmic ray events for analysis. Due to a rigorous pre-deployment protocol, 98.4% of the DOMs in the deep ice are operating and collecting data. IceCube routinely achieves a detector uptime of 99% by emphasizing software stability and monitoring. Detector operations have been stable since construction was completed, and the detector is expected to operate at least until the end of the next decade.

Keywords
Large detector systems for particle and astroparticle physics, Neutrino detectors, Online farms and online filtering, Trigger concepts and systems (hardware and software)
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-147200 (URN)10.1088/1748-0221/12/03/P03012 (DOI)000406997600012 ()2-s2.0-85017394006 (Scopus ID)
Available from: 2017-09-18 Created: 2017-09-18 Last updated: 2022-10-20Bibliographically approved
Ahrens, M., Bohm, C., Dumm, J. P., Finley, C., Flis, S., Hulth, P. O., . . . Zoll, M. (2016). AN ALL-SKY SEARCH FOR THREE FLAVORS OF NEUTRINOS FROM GAMMA-RAY BURSTS WITH THE ICECUBE NEUTRINO OBSERVATORY. Astrophysical Journal, 824(2), Article ID 115.
Open this publication in new window or tab >>AN ALL-SKY SEARCH FOR THREE FLAVORS OF NEUTRINOS FROM GAMMA-RAY BURSTS WITH THE ICECUBE NEUTRINO OBSERVATORY
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2016 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 824, no 2, article id 115Article in journal (Refereed) Published
Abstract [en]

We present the results and methodology of a search for neutrinos produced in the decay of charged pions created in interactions between protons and gamma-rays during the prompt emission of 807 gamma-ray bursts (GRBs) over the entire sky. This three-year search is the first in IceCube for shower-like Cherenkov light patterns from electron, muon, and tau neutrinos correlated with GRBs. We detect five low-significance events correlated with five GRBs. These events are consistent with the background expectation from atmospheric muons and neutrinos. The results of this search in combination with those of IceCube's four years of searches for track-like Cherenkov light patterns from muon neutrinos correlated with Northern-Hemisphere GRBs produce limits that tightly constrain current models of neutrino and ultra high energy cosmic ray production in GRB fireballs.

Keywords
gamma-ray burst: general, methods: data analysis, neutrinos, telescopes
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-134177 (URN)10.3847/0004-637X/824/2/115 (DOI)000381912800051 ()2-s2.0-84978301509 (Scopus ID)
Available from: 2016-10-28 Created: 2016-10-03 Last updated: 2022-10-17Bibliographically approved
Ahrens, M., Bohm, C., Dumm, J. P., Finley, C., Flis, S., Hulth, P. O., . . . Zoll, M. (2016). ANISOTROPY IN COSMIC-RAY ARRIVAL DIRECTIONS IN THE SOUTHERN HEMISPHERE BASED ON SIX YEARS OF DATA FROM THE ICECUBE DETECTOR. Astrophysical Journal, 826(2), Article ID 220.
Open this publication in new window or tab >>ANISOTROPY IN COSMIC-RAY ARRIVAL DIRECTIONS IN THE SOUTHERN HEMISPHERE BASED ON SIX YEARS OF DATA FROM THE ICECUBE DETECTOR
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2016 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 826, no 2, article id 220Article in journal (Refereed) Published
Abstract [en]

The IceCube Neutrino Observatory accumulated a total of 318 billion cosmic-ray-induced muon events between 2009 May and 2015 May. This data set was used for a detailed analysis of the sidereal anisotropy in the arrival directions of cosmic rays in the TeV to PeV energy range. The observed global sidereal anisotropy features large regions of relative excess and deficit, with amplitudes of the order of 10(-3) up to about 100 TeV. A decomposition of the arrival direction distribution into spherical harmonics shows that most of the power is contained in the low-multipole (l <= 4) moments. However, higher multipole components are found to be statistically significant down to an angular scale of less than 10 degrees, approaching the angular resolution of the detector. Above 100 TeV, a change in the morphology of the arrival direction distribution is observed, and the anisotropy is characterized by a wide relative deficit whose amplitude increases with primary energy up to at least 5 PeV, the highest energies currently accessible to IceCube. No time dependence of the large-and small-scale structures is observed in the period of six years covered by this analysis. The high-statistics data set reveals more details of the properties of the anisotropy and is potentially able to shed light on the various physical processes that are responsible for the complex angular structure and energy evolution.

Keywords
astroparticle physics, cosmic rays
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-134446 (URN)10.3847/0004-637X/826/2/220 (DOI)000381977900120 ()2-s2.0-84982224440 (Scopus ID)
Available from: 2016-10-10 Created: 2016-10-06 Last updated: 2022-10-17Bibliographically approved
Ahrens, M., Bohm, C., Dumm, J. P., Finley, C., Flis, S., Hulth, P. O., . . . Zoll, M. (2016). Characterization of the atmospheric muon flux in IceCube. Astroparticle physics, 78, 1-27
Open this publication in new window or tab >>Characterization of the atmospheric muon flux in IceCube
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2016 (English)In: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 78, p. 1-27Article in journal (Refereed) Published
Abstract [en]

Muons produced in atmospheric cosmic ray showers account for the by far dominant part of the event yield in large-volume underground particle detectors. The IceCube detector, with an instrumented volume of about a cubic kilometer, has the potential to conduct unique investigations on atmospheric muons by exploiting the large collection area and the possibility to track particles over a long distance. Through detailed reconstruction of energy deposition along the tracks, the characteristics of muon bundles can be quantified, and individual particles of exceptionally high energy identified. The data can then be used to constrain the cosmic ray primary flux and the contribution to atmospheric lepton fluxes from prompt decays of short-lived hadrons. In this paper, techniques for the extraction of physical measurements from atmospheric muon events are described and first results are presented. The multiplicity spectrum of TeV muons in cosmic ray air showers for primaries in the energy range from the knee to the ankle is derived and found to be consistent with recent results from surface detectors. The single muon energy spectrum is determined up to PeV energies and shows a clear indication for the emergence of a distinct spectral component from prompt decays of short-lived hadrons. The magnitude of the prompt flux, which should include a substantial contribution from light vector meson di-muon decays, is consistent with current theoretical predictions. The variety of measurements and high event statistics can also be exploited for the evaluation of systematic effects. In the course of this study, internal inconsistencies in the zenith angle distribution of events were found which indicate the presence of an unexplained effect outside the currently applied range of detector systematics. The underlying cause could be related to the hadronic interaction models used to describe muon production in air showers.

Keywords
Atmospheric muons, Cosmic rays, Prompt leptons
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-130634 (URN)10.1016/j.astropartphys.2016.01.006 (DOI)000374612500001 ()2-s2.0-84958962340 (Scopus ID)
Available from: 2016-06-02 Created: 2016-05-27 Last updated: 2022-10-17Bibliographically approved
Ahrens, M., Bohm, C., Dumm, J. P., Finley, C., Flis, S., Hulth, P. O., . . . Zoll, M. (2016). High-energy neutrino follow-up search of gravitational wave event GW150914 with ANTARES and IceCube. Physical Review D, 93(12), Article ID 122010.
Open this publication in new window or tab >>High-energy neutrino follow-up search of gravitational wave event GW150914 with ANTARES and IceCube
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2016 (English)In: Physical Review D, ISSN 2470-0010, Vol. 93, no 12, article id 122010Article in journal (Refereed) Published
Abstract [en]

We present the high-energy-neutrino follow-up observations of the first gravitational wave transient GW150914 observed by the Advanced LIGO detectors on September 14, 2015. We search for coincident neutrino candidates within the data recorded by the IceCube and ANTARES neutrino detectors. A possible joint detection could be used in targeted electromagnetic follow-up observations, given the significantly better angular resolution of neutrino events compared to gravitational waves. We find no neutrino candidates in both temporal and spatial coincidence with the gravitational wave event. Within +/- 500 s of the gravitational wave event, the number of neutrino candidates detected by IceCube and ANTARES were three and zero, respectively. This is consistent with the expected atmospheric background, and none of the neutrino candidates were directionally coincident with GW150914. We use this nondetection to constrain neutrino emission from the gravitational-wave event.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-132395 (URN)10.1103/PhysRevD.93.122010 (DOI)000378308200001 ()2-s2.0-84976408194 (Scopus ID)
Available from: 2016-08-15 Created: 2016-08-11 Last updated: 2022-10-17Bibliographically approved
Ahrens, M., Bohm, C., Danninger, M., Dumm, J. P., Edsjö, J., Finley, C., . . . Zoll, M. (2016). Improved limits on dark matter annihilation in the Sun with the 79-string IceCube detector and implications for supersymmetry. Journal of Cosmology and Astroparticle Physics (4), Article ID 022.
Open this publication in new window or tab >>Improved limits on dark matter annihilation in the Sun with the 79-string IceCube detector and implications for supersymmetry
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2016 (English)In: Journal of Cosmology and Astroparticle Physics, E-ISSN 1475-7516, no 4, article id 022Article in journal (Refereed) Published
Abstract [en]

We present an improved event-level likelihood formalism for including neutrino telescope data in global fits to new physics. We derive limits on spin-dependent dark matter-proton scattering by employing the new formalism in a re-analysis of data from the 79-string IceCube search for dark matter annihilation in the Sun, including explicit energy information for each event. The new analysis excludes a number of models in the weak-scale minimal supersymmetric standard model (MSSM) for the first time. This work is accompanied by the public release of the 79-string IceCube data, as well as an associated computer code for applying the new likelihood to arbitrary dark matter models.

Keywords
dark matter experiments, dark matter theory, neutrino experiments
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-140379 (URN)10.1088/1475-7516/2016/04/022 (DOI)000393286400001 ()
Available from: 2017-03-27 Created: 2017-03-27 Last updated: 2023-03-28Bibliographically approved
Ahrens, M., Bohm, C., Dumm, J. P., Finley, C., Flis, S., Hulth, P. O., . . . Zoll, M. (2016). Neutrino oscillation studies with IceCube-DeepCore. Nuclear Physics B, 908, 161-177
Open this publication in new window or tab >>Neutrino oscillation studies with IceCube-DeepCore
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2016 (English)In: Nuclear Physics B, ISSN 0550-3213, E-ISSN 1873-1562, Vol. 908, p. 161-177Article in journal (Refereed) Published
Abstract [en]

IceCube, a gigaton-scale neutrino detector located at the South Pole, was primarily designed to search for astrophysical neutrinos with energies of PeV and higher. This goal has been achieved with the detection of the highest energy neutrinos to date. At the other end of the energy spectrum, the DeepCore extension lowers the energy threshold of the detector to approximately 10 GeV and opens the door for oscillation studies using atmospheric neutrinos. An analysis of the disappearance of these neutrinos has been completed, with the results produced being complementary with dedicated oscillation experiments. Following a review of the detector principle and performance, the method used to make these calculations, as well as the results, is detailed. Finally, the future prospects of IceCube-DeepCore and the next generation of neutrino experiments at the South Pole (IceCube-Gen2, specifically the PINGU sub-detector) are briefly discussed.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-131910 (URN)10.1016/j.nuclphysb.2016.03.028 (DOI)000377334000012 ()
Available from: 2016-07-06 Created: 2016-07-04 Last updated: 2022-03-23Bibliographically approved
Ahrens, M., Bohm, C., Dumm, J. P., Finley, C., Flis, S., Hulth, P. O., . . . Zoll, M. (2016). Search for astrophysical tau neutrinos in three years of IceCube data. Physical Review D, 93(2)
Open this publication in new window or tab >>Search for astrophysical tau neutrinos in three years of IceCube data
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2016 (English)In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 93, no 2Article in journal (Refereed) Published
Abstract [en]

The IceCube Neutrino Observatory has observed a diffuse flux of TeV-PeVastrophysical neutrinos at 5.7 sigma significance from an all-flavor search. The direct detection of tau neutrinos in this flux has yet to occur. Tau neutrinos become distinguishable from other flavors in IceCube at energies above a few hundred TeV, when the cascade from the tau neutrino charged current interaction becomes resolvable from the cascade from the tau lepton decay. This paper presents results from the first dedicated search for tau neutrinos with energies between 214 TeV and 72 PeV in the full IceCube detector. The analysis searches for IceCube optical sensors that observe two separate pulses in a single event-one from the tau neutrino interaction and a second from the tau decay. No candidate events were observed in three years of IceCube data. For the first time, a differential upper limit on astrophysical tau neutrinos is derived around the PeV energy region, which is nearly 3 orders of magnitude lower in energy than previous limits from dedicated tau neutrino searches.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-126906 (URN)10.1103/PhysRevD.93.022001 (DOI)000367897600001 ()2-s2.0-84955459064 (Scopus ID)
Available from: 2016-02-16 Created: 2016-02-16 Last updated: 2022-10-18Bibliographically approved
Ahrens, M., Bohm, C., Dumm, J. P., Finley, C., Flis, S., Hulth, P. O., . . . Zoll, M. (2016). Search for correlations between the arrival directions of IceCube neutrino events and ultrahigh-energy cosmic rays detected by the Pierre Auger Observatory and the Telescope Array. Journal of Cosmology and Astroparticle Physics (1), Article ID 037.
Open this publication in new window or tab >>Search for correlations between the arrival directions of IceCube neutrino events and ultrahigh-energy cosmic rays detected by the Pierre Auger Observatory and the Telescope Array
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2016 (English)In: Journal of Cosmology and Astroparticle Physics, E-ISSN 1475-7516, no 1, article id 037Article in journal (Refereed) Published
Abstract [en]

This paper presents the results of different searches for correlations between very high-energy neutrino candidates detected by IceCube and the highest-energy cosmic rays measured by the Pierre Auger Observatory and the Telescope Array. We first consider samples of cascade neutrino events and of high-energy neutrino-induced muon tracks, which provided evidence for a neutrino flux of astrophysical origin, and study their cross-correlation with the ultrahigh-energy cosmic ray (UHECR) samples as a function of angular separation. We also study their possible directional correlations using a likelihood method stacking the neutrino arrival directions and adopting different assumptions on the size of the UHECR magnetic deflections. Finally, we perform another likelihood analysis stacking the UHECR directions and using a sample of through-going muon tracks optimized for neutrino point-source searches with sub-degree angular resolution. No indications of correlations at discovery level are obtained for any of the searches performed. The smallest of the p-values comes from the search for correlation between UHECRs with IceCube high-energy cascades, a result that should continue to be monitored.

Keywords
neutrino experiments, ultra high energy cosmic rays, cosmic ray experiments, neutrino astronomy
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-127902 (URN)10.1088/1475-7516/2016/01/037 (DOI)000369734300037 ()2-s2.0-84957795133 (Scopus ID)
Available from: 2016-03-22 Created: 2016-03-14 Last updated: 2023-03-28Bibliographically approved
Ahrens, M., Bohm, C., Dumm, J. P., Finley, C., Flis, S., Hulth, P. O., . . . Zoll, M. (2016). Searches for relativistic magnetic monopoles in IceCube. European Physical Journal C, 76(3), Article ID 133.
Open this publication in new window or tab >>Searches for relativistic magnetic monopoles in IceCube
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2016 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 76, no 3, article id 133Article in journal (Refereed) Published
Abstract [en]

Various extensions of the Standard Model motivate the existence of stable magnetic monopoles that could have been created during an early high-energy epoch of the Universe. These primordial magnetic monopoles would be gradually accelerated by cosmic magnetic fields and could reach high velocities that make them visible in Cherenkov detectors such as IceCube. Equivalently to electrically charged particles, magnetic monopoles produce direct and indirect Cherenkov light while traversing through matter at relativistic velocities. This paper describes searches for relativistic (nu >= 0.76 c) and mildly relativistic (nu >= 0.51 c) monopoles, each using one year of data taken in 2008/2009 and 2011/2012, respectively. No monopole candidate was detected. For a velocity above 0.51 c the monopole flux is constrained down to a level of 1.55 x 10(-18) cm(-2) s(-1) sr(-1). This is an improvement of almost two orders of magnitude over previous limits.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-129698 (URN)10.1140/epjc/s10052-016-3953-8 (DOI)000372294300002 ()
Available from: 2016-05-06 Created: 2016-04-27 Last updated: 2022-03-23Bibliographically approved
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