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Browsing Chemistry and Physics publications by Author "Aartsen, M."
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Item Metadata only Characterization of the atmospheric muon flux in IceCube(Elsevier Science BV, 2016) Aartsen, M.; Abraham, K.; Ackermann, M.; Adams, J.; Aguilar, J.; Ahlers, M.; Ahrens, M.; Altmann, D.; Anderson, T.; Archinger, M.; Argüelles, C.; Arlen, T.; Auffenberg, J.; Bai, X.; Barwick, S.; Baum, V.; Bay, R.; Beatty, J.; Becker Tjus, J.; Becker, K.; et al.Abstract not availableItem Metadata only Determining neutrino oscillation parameters from atmospheric muon neutrino disappearance with three years of IceCube Deepcore data(American Physical Society, 2015) Aartsen, M.; Ackermann, M.; Adams, J.; Aguilar, J.; Ahlers, M.; Ahrens, M.; Altmann, D.; Anderson, T.; Arguelles, C.; Arlen, T.; Auffenberg, J.; Bai, X.; Barwick, S.; Baum, V.; Bay, R.; Beatty, J.; Becker Tjus, J.; Becker, K.; Benzvi, S.; Berghaus, P.; et al.We present a measurement of neutrino oscillations via atmospheric muon neutrino disappearance with three years of data of the completed IceCube neutrino detector. DeepCore, a region of denser IceCube instrumentation, enables the detection and reconstruction of atmospheric muon neutrinos between 10 and 100 GeV, where a strong disappearance signal is expected. The IceCube detector volume surrounding DeepCore is used as a veto region to suppress the atmospheric muon background. Neutrino events are selected where the detected Cherenkov photons of the secondary particles minimally scatter, and the neutrino energy and arrival direction are reconstructed. Both variables are used to obtain the neutrino oscillation parameters from the data, with the best fit given by Δm232=2.72+0.19−0.20×10−3 eV2 and sin2θ23=0.53+0.09−0.12 (normal mass ordering assumed). The results are compatible, and comparable in precision, to those of dedicated oscillation experiments.Item Metadata only Energy reconstruction methods in the IceCube neutrino telescope(IOP Publishing for Sissa Medialab, 2014) Aartsen, M.; Abbasi, R.; Ackermann, M.; Adams, J.; Aguilar, J.; Ahlers, M.; Altmann, D.; Arguelles, C.; Auffenberg, J.; Bai, X.; Baker, M.; Barwick, S.; Baum, V.; Bay, R.; Beatty, J.; Tjus, J.; Becker, K.; Benzvi, S.; Berghaus, P.; Berley, D.; et al.Accurate measurement of neutrino energies is essential to many of the scientific goals of large-volume neutrino telescopes. The fundamental observable in such detectors is the Cherenkov light produced by the transit through a medium of charged particles created in neutrino interactions. The amount of light emitted is proportional to the deposited energy, which is approximately equal to the neutrino energy for ne and nm charged-current interactions and can be used to set a lower bound on neutrino energies and to measure neutrino spectra statistically in other channels. Here we describe methods and performance of reconstructing charged-particle energies and topologies from the observed Cherenkov light yield, including techniques to measure the energies of uncontained muon tracks, achieving average uncertainties in electromagnetic-equivalent deposited energy of 15% above 10 TeV.Item Metadata only Evidence for astrophysical muon neutrinos from the northern sky with IceCube(American Physical Society, 2015) Aartsen, M.; Abraham, K.; Ackermann, M.; Adams, J.; Aguilar, J.; Ahlers, M.; Ahrens, M.; Altmann, D.; Anderson, T.; Archinger, M.; Arguelles, C.; Arlen, T.; Auffenberg, J.; Bai, X.; Barwick, S.; Baum, V.; Bay, R.; Beatty, J.; Tjus, J.; Becker, K.; et al.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 νe and ντ 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(Eν)=9.9+3.9−3.4×10−19 GeV−1 cm−2 sr−1 s−1(Eν/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.Item Metadata only First observation of PeV-energy neutrinos with IceCube(American Physical Soc, 2013) Aartsen, M.; Hill, G.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) (ν̅ (e,μ,τ)) or charged-current ν(e) (ν̅ 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.Item Metadata only Flavor ratio of astrophysical neutrinos above 35 TeV in IceCube(American Physical Society, 2015) Aartsen, M.; Ackermann, M.; Adams, J.; Aguilar, J.; Ahlers, M.; Ahrens, M.; Altmann, D.; Anderson, T.; Arguelles, C.; Arlen, T.; Auffenberg, J.; Bai, X.; Barwick, S.; Baum, V.; Bay, R.; Beatty, J.; Becker Tjus, J.; Becker, K.; Benzvi, S.; Berghaus, P.; et al.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.Item Metadata only IceCube search for dark matter annihilation in nearby galaxies and galaxy clusters(American Physical Society, 2013) Aartsen, M.; Abbasi, R.; Abdou, Y.; Ackermann, M.; Adams, J.; Aguilar, J.; Ahlers, M.; Altmann, D.; Auffenberg, J.; Bai, X.; Baker, M.; Barwick, S.; Baum, V.; Bay, R.; Beatty, J.; Bechet, S.; Becker Tjus, J.; Becker, K.-H.; Benabderrahmane, M.; BenZvi, S.; et al.We present the results of a first search for self-annihilating dark matter in nearby galaxies and galaxy clusters using a sample of high-energy neutrinos acquired in 339.8 days of live time during 2009/10 with the IceCube neutrino observatory in its 59-string configuration. The targets of interest include the Virgo and Coma galaxy clusters, the Andromeda galaxy, and several dwarf galaxies. We obtain upper limits on the cross section as a function of the weakly interacting massive particle mass between 300 GeV and 100 TeV for the annihilation into bb¯, W+W−, τ+τ−, μ+μ−, and νν¯. A limit derived for the Virgo cluster, when assuming a large effect from subhalos, challenges the weakly interacting massive particle interpretation of a recently observed GeV positron excess in cosmic rays.Item Metadata only LUNASKA neutrino search with the Parkes and ATCA telescopes(AIP Publishing, 2013) Bray, J.; Ekers, R.; Protheroe, R.; James, C.; Phillips, C.; Roberts, P.; Brown, A.; Reynolds, J.; McFadden, R.; Aartsen, M.; 5th International Workshop on Acoustic and Radio EeV Neutrino Detection Activities: ARENA 2012 (19 Jun 2012 - 22 Jun 2012 : Erlangen, Germany); Lahmann, R.; Eberl, T.; Graf, K.; James, C.; Huege, T.; Karg, T.; Nahnhauer, R.The Moon is used as a target volume for ultra-high energy neutrino searches with terrestrial radio telescopes. The LUNASKA project has conducted observations with the Parkes and ATCA telescopes; and, most recently, with both of them in combination. We present an analysis of the data obtained from these searches, including validation and calibration results for the Parkes-ATCA experiment, as well as a summary of prospects for future observations.Item Open Access Measurement of atmospheric neutrino oscillations with IceCube(American Physical Soc, 2013) Aartsen, M.; Hill, G.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.Item Metadata only Measurement of South Pole ice transparency with the IceCube LED calibration system(Elsevier Science BV, 2013) Aartsen, M.; Hill, G.The IceCube Neutrino Observatory, approximately 1 km³ in size, is now complete with 86 strings deployed in the Antarctic ice. IceCube detects the Cherenkov radiation emitted by charged particles passing through or created in the ice. To realize the full potential of the detector, the properties of light propagation in the ice in and around the detector must be well understood. This report presents a new method of fitting the model of light propagation in the ice to a data set of in situ light source events collected with IceCube. The resulting set of derived parameters, namely the measured values of scattering and absorption coefficients vs. depth, is presented and a comparison of IceCube data with simulations based on the new model is shown.Item Metadata only Measurement of the atmospheric νe spectrum with IceCube(American Physical Society, 2015) Aartsen, M.; Ackermann, M.; Adams, J.; Aguilar, J.; Ahlers, M.; Ahrens, M.; Altmann, D.; Anderson, T.; Archinger, M.; Arguelles, C.; Arlen, T.; Auffenberg, J.; Bai, X.; Barwick, S.; Baum, V.; Bay, R.; Beatty, J.; Becker Tjus, J.; Becker, K.; Beiser, E.; et al.We present a measurement of the atmospheric νe spectrum at energies between 0.1 and 100 TeV using data from the first year of the complete IceCube detector. Atmospheric νe originate mainly from the decays of kaons produced in cosmic-ray air showers. This analysis selects 1078 fully contained events in 332 days of live time, and then identifies those consistent with particle showers. A likelihood analysis with improved event selection extends our previous measurement of the conventional νe fluxes to higher energies. The data constrain the conventional νe flux to be 1.3+0.4−0.3 times a baseline prediction from a Honda’s calculation, including the knee of the cosmic-ray spectrum. A fit to the kaon contribution (ξ) to the neutrino flux finds a kaon component that is ξ=1.3+0.5−0.4 times the baseline value. The fitted/measured prompt neutrino flux from charmed hadron decays strongly depends on the assumed astrophysical flux and shape. If the astrophysical component follows a power law, the result for the prompt flux is 0.0+3.0−0.0 times a calculated flux based on the work by Enberg, Reno, and Sarcevic.Item Metadata only Measurement of the atmospheric νₑ flux in IceCube(American Physical Soc, 2013) Aartsen, M.; Hill, G.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.Item Open Access Measurement of the cosmic ray energy spectrum with IceTop-73(American Physical Soc, 2013) Aartsen, M.; Hill, G.We report on the measurement of the all-particle cosmic ray energy spectrum with the IceTop air shower array in the energy range from 1.58 PeV to 1.26 EeV. The IceTop air shower array is the surface component of the IceCube Neutrino Observatory at the geographical South Pole. The analysis was performed using only information from IceTop. The data used in this work were taken from June 1, 2010 to May 13, 2011. During that period the IceTop array consisted of 73 stations, compared to 81 in its final configuration. The measured spectrum exhibits a clear deviation from a single power law above the knee around 4 PeV and below 1 EeV. We observe spectral hardening around 18 PeV and steepening around 130 PeV.Item Metadata only Multipole analysis of IceCube data to search for dark matter accumulated in the Galactic halo(Springer Berlin Heidelberg, 2015) Aartsen, M.; Ackermann, M.; Adams, J.; Aguilar, J.; Ahlers, M.; Ahrens, M.; Altmann, D.; Anderson, T.; Arguelles, C.; Arlen, T.; Auffenberg, J.; Bai, X.; Barwick, S.; Baum, V.; Beatty, J.; Becker Tjus, J.; Becker, K.; BenZvi, S.; Berghaus, P.; Berley, D.; et al.Dark matter which is bound in the Galactic halo might self-annihilate and produce a flux of stable final state particles, e.g. high energy neutrinos. These neutrinos can be detected with IceCube, a cubic-kilometer sized Cherenkov detector. Given IceCube’s large field of view, a characteristic anisotropy of the additional neutrino flux is expected. In this paper we describe a multipole method to search for such a large-scale anisotropy in IceCube data. This method uses the expansion coefficients of a multipole expansion of neutrino arrival directions and incorporates signal-specific weights for each expansion coefficient. We apply the technique to a high-purity muon neutrino sample from the Northern Hemisphere. The final result is compatible with the null-hypothesis. As no signal was observed, we present limits on the self-annihilation cross-section averaged over the relative velocity distribution ⟨σΑv⟩ down to 1.9×10¯²³cm³s¯¹ for a dark matter particle mass of 700–1,000 GeV and direct annihilation into νν¯. The resulting exclusion limits come close to exclusion limits from γ-ray experiments, that focus on the outer Galactic halo, for high dark matter masses of a few TeV and hard annihilation channels.Item Metadata only Observation of cosmic-ray anisotropy with the icetop air shower array(Univ Chicago Press, 2013) Aartsen, M.; Hill, G.We report on the observation of anisotropy in the arrival direction distribution of cosmic rays at PeV energies. The analysis is based on data taken between 2009 and 2012 with the IceTop air shower array at the south pole. IceTop, an integral part of the IceCube detector, is sensitive to cosmic rays between 100 TeV and 1 EeV. With the current size of the IceTop data set, searches for anisotropy at the 10⁻³ level can, for the first time, be extended to PeV energies. We divide the data set into two parts with median energies of 400 TeV and 2 PeV, respectively. In the low energy band, we observe a strong deficit with an angular size of about 30° and an amplitude of (– 1.58 ± 0.46(stat) ± 0.52(sys)) × 10⁻³ at a location consistent with previous observations of cosmic rays with the IceCube neutrino detector. The study of the high energy band shows that the anisotropy persists to PeV energies and increases in amplitude to (– 3.11 ± 0.38(stat) ± 0.96(sys)) × 10⁻³.Item Metadata only Observation of high-energy astrophysical neutrinos in three years of IceCube data(American Physical Society, 2014) Aartsen, M.; Ackermann, M.; Adams, J.; Aguilar, J.; Ahlers, M.; Ahrens, M.; Altmann, D.; Anderson, T.; Arguelles, C.; Arlen, T.; Auffenberg, J.; Bai, X.; Barwick, S.; Baum, V.; Beatty, J.; Becker Tjus, J.; Becker, K.; Benzvi, S.; Berghaus, P.; Berley, D.; et al.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.Item Metadata only Observation of the cosmic-ray shadow of the Moon with IceCube(American Physical Society, 2014) Aartsen, M.; Abbasi, R.; Abdou, Y.; Ackermann, M.; Adams, J.; Aguilar, J.; Ahlers, M.; Altmann, D.; Auffenberg, J.; Bai, X.; Baker, M.; Barwick, S.; Baum, V.; Bay, R.; Beatty, J.; Bechet, S.; Becker Tjus, J.; Becker, K.; Bell, M.; Benabderrahmane, M.; et al.We report on the observation of a significant deficit of cosmic rays from the direction of the Moon with the IceCube detector. The study of this “Moon shadow” is used to characterize the angular resolution and absolute pointing capabilities of the detector. The detection is based on data taken in two periods before the completion of the detector: between April 2008 and May 2009, when IceCube operated in a partial configuration with 40 detector strings deployed in the South Pole ice, and between May 2009 and May 2010 when the detector operated with 59 strings. Using two independent analysis methods, the Moon shadow has been observed to high significance (>6σ) in both detector configurations. The observed location of the shadow center is within 0.2° of its expected position when geomagnetic deflection effects are taken into account. This measurement validates the directional reconstruction capabilities of IceCube.Item Metadata only Probing the origin of cosmic rays with extremely high energy neutrinos using the IceCube Observatory(American Physical Society, 2013) Aartsen, M.; Abbasi, R.; Ackermann, M.; Adams, J.; Aguilar, J.; Ahlers, M.; Altmann, D.; Arguelles, C.; Auffenberg, J.; Bai, X.; Baker, M.; Barwick, S.; Baum, V.; Bay, R.; Beatty, J.; Becker Tjus, J.; Becker, K.; BenZvi, S.; Berghaus, P.; Berley, D.; et al.We have searched for extremely high energy neutrinos using data taken with the IceCube detector between May 2010 and May 2012. Two neutrino-induced particle shower events with energies around 1 PeV were observed, as reported previously. In this work, we investigate whether these events could originate from cosmogenic neutrinos produced in the interactions of ultrahigh energy cosmic rays with ambient photons while propagating through intergalactic space. Exploiting IceCube’s large exposure for extremely high energy neutrinos and the lack of observed events above 100 PeV, we can rule out the corresponding models at more than 90% confidence level. The model-independent quasidifferential 90% C.L. upper limit, which amounts to E2ϕνe+νμ+ντ=1.2×10−7 GeV cm−2 s−1 sr−1 at 1 EeV, provides the most stringent constraint in the energy range from 10 PeV to 10 EeV. Our observation disfavors strong cosmological evolution of the highest energy cosmic-ray sources such as the Fanaroff-Riley type II class of radio galaxies.Item Metadata only Search for a diffuse flux of astrophysical muon neutrinos with the IceCube 59-string configuration(American Physical Society, 2014) Aartsen, M.; Abbasi, R.; Ackermann, M.; Adams, J.; Aguilar, J.; Ahlers, M.; Altmann, D.; Arguelles, C.; Arlen, T.; Auffenberg, J.; Bai, X.; Baker, M.; Barwick, S.; Baum, V.; Bay, R.; Beatty, J.; Becker Tjus, J.; Becker, K.; Benzvi, S.; Berghaus, P.; et al.A search for high-energy neutrinos was performed using data collected by the IceCube Neutrino Observatory from May 2009 to May 2010, when the array was running in its 59-string configuration. The data sample was optimized to contain muon neutrino induced events with a background contamination of atmospheric muons of less than 1%. These data, which are dominated by atmospheric neutrinos, are analyzed with a global likelihood fit to search for possible contributions of prompt atmospheric and astrophysical neutrinos, neither of which have yet been identified. Such signals are expected to follow a harder energy spectrum than conventional atmospheric neutrinos. In addition, the zenith angle distribution differs for astrophysical and atmospheric signals. A global fit of the reconstructed energies and directions of observed events is performed, including possible neutrino flux contributions for an astrophysical signal and atmospheric backgrounds as well as systematic uncertainties of the experiment and theoretical predictions. The best fit yields an astrophysical signal flux for νμ+ν¯μ of E2⋅Φ(E)=0.25×10−8 GeV cm−2 s−1 sr−1, and a zero prompt component. Although the sensitivity of this analysis for astrophysical neutrinos surpasses the Waxman and Bahcall upper bound, the experimental limit at 90% confidence level is a factor of 1.5 above at a flux of E2⋅Φ(E)=1.44×10−8 GeV cm−2 s−1 sr−1.Item Metadata only Search for astrophysical tau neutrinos in three years of IceCube data(American Physical Society, 2016) Aartsen, M.; Abraham, K.; Ackermann, M.; Adams, J.; Aguilar, J.; Ahlers, M.; Ahrens, M.; Altmann, D.; Anderson, T.; Ansseau, I.; Archinger, M.; Arguelles, C.; Arlen, T.; Auffenberg, J.; Bai, X.; Barwick, S.; Baum, V.; Bay, R.; Beatty, J.; Becker Tjus, J.; et al.The IceCube Neutrino Observatory has observed a diffuse flux of TeV-PeV astrophysical neutrinos at 5.7σ 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.