More than 10,000 photomultiplier tubes (PMTs) with a diameter of 80 mm will be installed in multi-PMT Digital Optical Modules (mDOMs) of the IceCube Upgrade. These have been tested and pre-calibrated ...at two sites. A throughput of more than 1000 PMTs per week with both sites was achieved with a modular design of the testing facilities and highly automated testing procedures. The testing facilities can easily be adapted to other PMTs, such that they can, e.g., be re-used for testing the PMTs for IceCube-Gen2. Single photoelectron response, high voltage dependence, time resolution, prepulse, late pulse, afterpulse probabilities, and dark rates were measured for each PMT. We describe the design of the testing facilities, the testing procedures, and the results of the acceptance tests.
The recent IceCube detection of TeV neutrino emission from the nearby active galaxy NGC 1068 suggests that active galactic nuclei (AGN) could make a sizable contribution to the diffuse flux of ...astrophysical neutrinos. The absence of TeV \(\gamma\)-rays from NGC 1068 indicates neutrino production in the vicinity of the supermassive black hole, where the high radiation density leads to \(\gamma\)-ray attenuation. Therefore, any potential neutrino emission from similar sources is not expected to correlate with high-energy \(\gamma\)-rays. Disk-corona models predict neutrino emission from Seyfert galaxies to correlate with keV X-rays, as they are tracers of coronal activity. Using through-going track events from the Northern Sky recorded by IceCube between 2011 and 2021, we report results from a search for individual and aggregated neutrino signals from 27 additional Seyfert galaxies that are contained in the BAT AGN Spectroscopic Survey (BASS). Besides the generic single power-law, we evaluate the spectra predicted by the disk-corona model. Assuming all sources to be intrinsically similar to NGC 1068, our findings constrain the collective neutrino emission from X-ray bright Seyfert galaxies in the Northern Hemisphere, but, at the same time, show excesses of neutrinos that could be associated with the objects NGC 4151 and CGCG 420-015. These excesses result in a 2.7\(\sigma\) significance with respect to background expectations.
The IceCube Neutrino Observatory relies on an array of photomultiplier tubes to detect Cherenkov light produced by charged particles in the South Pole ice. IceCube data analyses depend on an in-depth ...characterization of the glacial ice, and on novel approaches in event reconstruction that utilize fast approximations of photoelectron yields. Here, a more accurate model is derived for event reconstruction that better captures our current knowledge of ice optical properties. When evaluated on a Monte Carlo simulation set, the median angular resolution for in-ice particle showers improves by over a factor of three compared to a reconstruction based on a simplified model of the ice. The most substantial improvement is obtained when including effects of birefringence due to the polycrystalline structure of the ice. When evaluated on data classified as particle showers in the high-energy starting events sample, a significantly improved description of the events is observed.
We provide supporting details for the search for a 3+1 sterile neutrino using
data collected over eleven years at the IceCube Neutrino Observatory. The
analysis uses atmospheric muon-flavored ...neutrinos from 0.5 to 100\, TeV that
traverse the Earth to reach the IceCube detector, and finds a best-fit point at
$\sin^2(2\theta_{24}) = 0.16$ and $\Delta m^{2}_{41} = 3.5$ eV$^2$ with a
goodness-of-fit p-value of 12\% and consistency with the null hypothesis of no
oscillations to sterile neutrinos with a p-value of 3.1\%. Several improvements
were made over past analyses, which are reviewed in this article, including
upgrades to the reconstruction and the study of sources of systematic
uncertainty. We provide details of the fit quality and discuss stability tests
that split the data for separate samples, comparing results. We find that the
fits are consistent between split data sets.
This Letter presents the result of a 3+1 sterile neutrino search using 10.7
years of IceCube data. We analyze atmospheric muon neutrinos that traverse the
Earth with energies ranging from 0.5 to 100 ...TeV, incorporating significant
improvements in modeling neutrino flux and detector response compared to
earlier studies. Notably, for the first time, we categorize data into starting
and through-going events, distinguishing neutrino interactions with vertices
inside or outside the instrumented volume, to improve energy resolution. The
best-fit point for a 3+1 model is found to be at $\sin^2(2\theta_{24}) = 0.16$
and $\Delta m^{2}_{41} = 3.5$ eV$^2$, which agrees with previous iterations of
this study. The result is consistent with the null hypothesis of no sterile
neutrinos with a p-value of 3.1\%.
We present a catalog of likely astrophysical neutrino track-like events from the IceCube Neutrino Observatory. IceCube began reporting likely astrophysical neutrinos in 2016 and this system was ...updated in 2019. The catalog presented here includes events that were reported in real-time since 2019, as well as events identified in archival data samples starting from 2011. We report 275 neutrino events from two selection channels as the first entries in the catalog, the IceCube Event Catalog of Alert Tracks, which will see ongoing extensions with additional alerts. The gold and bronze alert channels respectively provide neutrino candidates with 50\% and 30\% probability of being astrophysical, on average assuming an astrophysical neutrino power law energy spectral index of 2.19. For each neutrino alert, we provide the reconstructed energy, direction, false alarm rate, probability of being astrophysical in origin, and likelihood contours describing the spatial uncertainty in the alert's reconstructed location. We also investigate a directional correlation of these neutrino events with gamma-ray and X-ray catalogs including 4FGL, 3HWC, TeVCat and Swift-BAT.
We present the results of a search for 10--1,000 GeV neutrinos from 2,268 gamma-ray bursts over 8 years of IceCube-DeepCore data. This work probes burst physics below the photosphere where ...electromagnetic radiation cannot escape. Neutrinos of tens of GeVs are predicted in sub-photospheric collision of free streaming neutrons with bulk-jet protons. In a first analysis, we searched for the most significant neutrino-GRB coincidence using six overlapping time windows centered on the prompt phase of each GRB. In a second analysis, we conducted a search for a group of GRBs, each individually too weak to be detectable, but potentially significant when combined. No evidence of neutrino emission is found for either analysis. The most significant neutrino coincidence is for Fermi-GBM GRB bn 140807500, with a p-value of 0.097 corrected for all trials. The binomial test used to search for a group of GRBs had a p-value of 0.65 after all trial corrections. The binomial test found a group consisting only of GRB bn 140807500 and no additional GRBs. The neutrino limits of this work complement those obtained by IceCube at TeV to PeV energies. We compare our findings for the large set of GRBs as well as GRB 221009A to the sub-photospheric neutron-proton collision model and find that GRB 221009A provides the most constraining limit on baryon loading. For a jet Lorentz factor of 300 (800), the baryon loading on GRB 221009A is lower than 3.85 (2.13) at a 90% confidence level.
We report on a measurement of astrophysical tau neutrinos with 9.7 years of IceCube data. Using convolutional neural networks trained on images derived from simulated events, seven candidate ...\(\nu_\tau\) events were found with visible energies ranging from roughly 20 TeV to 1 PeV and a median expected parent \(\nu_\tau\) energy of about 200 TeV. Considering backgrounds from astrophysical and atmospheric neutrinos, and muons from \(\pi^\pm/K^\pm\) decays in atmospheric air showers, we obtain a total estimated background of about 0.5 events, dominated by non-\(\nu_\tau\) astrophysical neutrinos. Thus, we rule out the absence of astrophysical \(\nu_\tau\) at the \(5\sigma\) level. The measured astrophysical \(\nu_\tau\) flux is consistent with expectations based on previously published IceCube astrophysical neutrino flux measurements and neutrino oscillations.
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