Search For Neutrino Point Sources Research Articles

Neutrino point source searches for dark matter spikes

Any dark matter spikes surrounding black holes in our Galaxy are sites of significant dark matter annihilation, leading to a potentially detectable neutrino signal. In this paper we examine 10 - 105 M ⊙ black holes associated with dark matter spikes that formed in early minihalos and still exist in our Milky Way Galaxy today, in light of neutrino data from the ANTARES [1] and IceCube [2] detectors. In various regions of the sky, we determine the minimum distance away from the solar system that a dark matter spike must be in order to have not been detected as a neutrino point source for a variety of representative dark matter annihilation channels. Given these constraints on the distribution of dark matter spikes in the Galaxy, we place significant limits on the formation of the first generation of stars in early minihalos — stronger than previous limits from gamma-ray searches in Fermi Gamma-Ray Space Telescope data. The larger black holes considered in this paper may arise as the remnants of Dark Stars after the dark matter fuel is exhausted; thus neutrino observations may be used to constrain the properties of Dark Stars. The limits are particularly strong for heavier WIMPs. For WIMP masses ∼ 5TeV, we show that ≲ 10 % of minihalos can host first stars that collapse into BHs larger than 103 M ⊙.

A Search for Time-dependent Astrophysical Neutrino Emission with IceCube Data from 2012 to 2017

Abstract High-energy neutrinos are unique messengers of the high-energy universe, tracing the processes of cosmic ray acceleration. This paper presents analyses focusing on time-dependent neutrino point-source searches. A scan of the whole sky, making no prior assumption about source candidates, is performed, looking for a space and time clustering of high-energy neutrinos in data collected by the IceCube Neutrino Observatory between 2012 and 2017. No statistically significant evidence for a time-dependent neutrino signal is found with this search during this period, as all results are consistent with the background expectation. Within this study period, the blazar 3C 279, showed strong variability, inducing a very prominent gamma-ray flare observed in 2015 June. This event motivated a dedicated study of the blazar, which consists of searching for a time-dependent neutrino signal correlated with the gamma-ray emission. No evidence for a time-dependent signal is found. Hence, an upper limit on the neutrino fluence is derived, allowing us to constrain a hadronic emission model.

IceCube: An overview of physics results

Cosmic rays and neutrinos are intimately related. And though TeVPeV astrophysical neutrinos have been observed, their sources and their relation to potential sources of cosmic rays remain unknown. Recently, the blazar TXS 0506+056 has been identified as a candidate neutrino source. In parallel, IceCube has conducted numerous searches for other potential neutrino neutrino sources. These proceedings are limited in scope, given the large breath of science results by IceCube: A description of the astrophysical neutrino flux; a review of the real-time program that enables multi-messenger follow-up of neutrinos; a summary of the observations of TXS 0506+056; a recap of the search for neutrino point sources with 7 years of IceCube data; an account of the tantalizing capabilities of IceCube and ANTARES to detect Milky Way neutrinos and a description of a method to identify Glashow resonance events.

ANTARES-IceCube combined search for neutrino pointsources in the Southern Hemisphere

A search for cosmic neutrino point-like sources covering the Southern hemisphere is presented, using 9 years and 7 years of data from the ANTARES and IceCube neutrino telescopes, respectively. The advantageous field of view of ANTARES as well as the high statistics provided by IceCube are exploited to open a window in the Southern sky where the sensitivity to point-sources improves by a factor ~ 2 compared to individual analyses. An unbinned maximum likelihood method is used to search for a localised excess of muon events over the expected background. Before applying the method to the unblinded dataset, the sensitivity and discovery potential of the search are computed through dedicated pseudo-experiments.

Correlation between UHECRs measured by the Pierre Auger Observatory and Telescope Array and neutrino candidate events from IceCube

We present the results of three searches for correlations between ultra-high energy cosmic ray events (UHECRs) measured by Telescope Array and the Pierre Auger Observatory and high-energy neutrino candidate events from IceCube. Two cross-correlation analyses of UHECRs are done: one with 28 “cascades” from the IceCube ‘high-energy starting events’ sample and the other one with 12 high-energy “tracks”. The angular separation between the arrival directions of neutrinos and UHECRs is scanned. The same events are also used in a separate search stacking the neutrino arrival directions and using a maximum likelihood approach. We assume that UHECR magnetic deflections are inversely proportional to the energy with values 3°, 6° and 9° at 100 EeV to account for the various scenarios of the magnetic field strength and UHECR charges. A similar analysis is performed on stacked UHECR arrival directions and the IceCube 4-year sample of through-going muon-track events that was optimized for neutrino point source searches.

First combined search for neutrino point-sources in the southern sky with the ANTARES and IceCube neutrino telescopes

A search for cosmic neutrino point-like sources using the ANTARES and IceCube neutrino telescopes over the Southern Hemisphere is presented. The ANTARES data were collected between January 2007 and December 2012, whereas the IceCube data ranges from April 2008 to May 2011. An unbinned maximum likelihood method is used to search for a localized excess of muon events in the southern sky assuming an E − 2 neutrino source spectrum. A search over a pre-selected list of candidate sources has also been carried out for different source assumptions: spectral indices of 2.0 and 2.5, and energy cutoffs of 1 PeV, 300 TeV and 100 TeV. No significant excess over the background has been found, and upper limits for the candidate sources are presented compared to the individual experiments.

Correlation between the UHECRs measured by the Pierre Auger Observatory and Telescope Array and neutrino candidate events from IceCube

We present the results of three searches for correlations between ultra-high energy cosmic ray measured by Telescope Array and the Pierre Auger Observatory and neutrino candidate from IceCube. Two cross-correlation analyses of ultra-high energy cosmic rays are done: one with 39 cascades from the IceCube high-energy starting events sample and the other one with 16 tracks. The angular separation between the arrival directions of neutrinos and UHECRs is scanned. The same are also used in a separate search stacking the neutrino arrival directions and using a maximum likelihood approach. We assume that UHECR magnetic deflections are inversely proportional to the energy with values 3 ◦ ,6 ◦ and 9 ◦ at 100 EeV to account for the uncertainties in the magnetic field strength and UHECR charge. A similar analysis is performed on stacked UHECR arrival directions and the IceCube 4-year sample of through- going muon-track that was optimized for neutrino point source searches.

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

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.

SEARCH FOR TIME-INDEPENDENT NEUTRINO EMISSION FROM ASTROPHYSICAL SOURCES WITH 3 yr OF IceCube DATA

We present the results of a search for neutrino point sources using the IceCube data collected between April 2008 and May 2011 with three partially completed configurations of the detector: the 40-, 59- and 79-string configurations. The live-time of this data set are 1,040 days. An unbinned maximum likelihood ratio test was used to search for an excess of neutrinos above the atmospheric background at any given direction in the sky. By adding two more years of data with improved event selection and reconstruction techniques, the sensitivity was improved by a factor 3.5 or more with respect to the previously published results obtained with the 40-string configuration of IceCube. We performed an all-sky survey and a dedicated search using a catalog of \textit{a priori} selected objects observed by other telescopes. In both searches, the data are compatible with the background-only hypothesis. In the absence of evidence for a signal, we set upper limits on the flux of muon neutrinos. For an E$^{-2}$ neutrino spectrum, the observed limits are between 0.9 and $23.2\times 10^{-12}$ TeV$^{-1}$ cm$^{-2}$s$^{-1}$. We also report upper limits for neutrino emission from groups of sources which were selected according to theoretical models or observational parameters and analysed with a stacking approach.

Search for neutrino point sources with the IceCube Neutrino Observatory

The IceCube Neutrino Observatory is a kilometer-scale detector located at the South Pole. The full detector comprises 5,160 photomultipliers (PMTs) deployed among 86 strings from 1.5–2.5 km deep within the ice. The constructing phase started in the austral summer of 2004 and ended in December 2010 with the deployment of the last 7 strings that make up the full detector. In this proceeding we present the results of the time integrated and time dependent point source searches corresponding to the years from April 2008 to May 2010 with two different configurations of the IceCube detector (40 and 59 strings). In the northern sky the IceCube neutrino telescope is sensitive to point sources of neutrinos with E−2 spectra mainly in the TeV–PeV energy range. In the opposite hemisphere, due to the higher contamination of high-energy atmospheric muons, the detector is most sensitive to sources with harder spectra, which produce high fluxes of PeV to EeV energies. The combined sensitivity is about a factor ∼2.5 better than the previous 1-year limit. An overview of the sensitivity and discovery potential for the time integrated searches over three years of IceCube, from April 2008 to May 2011, is also shown.

Muon energy reconstruction in the ANTARES detector

The energy reconstruction of both neutrino-induced muons from neutrino interactions in the vicinity of the detector and of muons from cosmic ray air showers contributes indispensable information for a broad range of physics analyses, e.g. by increasing the sensitivity in neutrino point source searches or in offering access to observables such as the atmospheric neutrino spectrum. Currently, four energy reconstruction methods are implemented in the ANTARES data analysis framework, ranging from estimates based on photon counting and the total charge deposited in the detector to methods based on probability density functions and Artificial Neural Networks. These four methods, their performance and systematic studies of the energy resolution capabilities of the ANTARES detector are presented.

Extending the Search for Neutrino Point Sources with IceCube above the Horizon

Point source searches with the IceCube neutrino telescope have been restricted to one hemisphere, due to the exclusive selection of upward going events as a way of rejecting the atmospheric muon background. We show that the region above the horizon can be included by suppressing the background through energy-sensitive cuts. This improves the sensitivity above PeV energies, previously not accessible for declinations of more than a few degrees below the horizon due to the absorption of neutrinos in Earth. We present results based on data collected with 22 strings of IceCube, extending its field of view and energy reach for point source searches. No significant excess above the atmospheric background is observed in a sky scan and in tests of source candidates. Upper limits are reported, which for the first time cover point sources in the southern sky up to EeV energies.

SEARCH FOR ASTROPHYSICAL NEUTRINO POINT SOURCES AT SUPER-KAMIOKANDE

It has been hypothesized that large fluxes of neutrinos may be created in astrophysical "cosmic accelerators." The primary background for a search for astrophysical neutrinos comes from atmospheric neutrinos, which do not exhibit the pointlike directional clustering that characterizes a distant astrophysical signal. We perform a search for neutrino point sources using the upward-going muon data from three phases of operation (SK-I, SK-II, and SK-III) spanning 2623 days of live time taken from April 1, 1996 to August 11, 2007. The search looks for signals from suspected galactic and extragalactic sources, transient sources, and unexpected sources. We find interesting signatures from two objects--RX J1713.7-3946 (97.5% CL) and GRB 991004D (95.3% CL)--but the signatures lack compelling statistical significance given trial factors. We set limits on the flux and fluence of neutrino point sources above energies of 1.6 GeV.

Search for neutrino point sources with IceCube 22-strings

The IceCube detector took data in its 22-string configuration in 2007-2008. This data has been analyzed to search for extraterrestrial point sources of neutrinos using several methods. Two main methods are discussed and compared here: the binned and the unbinned maximum likelihood method. The best sky-averaged sensitivity (90% C.L.) is E^2 Phi_nu_mu=1.3 10^-11 TeVcm^-2s^-1 to a generic E^-2 flux of nu_mu over the energy range from 3 TeV to 3 PeV. No neutrino point sources are found from the individual directions of a pre-selected catalogue nor in a search extended to the northern sky. Limits are improved by a factor of two compared to the total statistics collected with the AMANDA-II detector and represent the best results to date.