ANTARES Neutrino Telescope Research Articles

Constraints on the energy spectrum of the diffuse cosmic neutrino flux from the ANTARES neutrino telescope

High-significance evidences of the existence of a high-energy diffuse flux of cosmic neutrinos have emerged in the last decade from several observations by the IceCube Collaboration. The ANTARES neutrino telescope took data for 15 years in the Mediterranean Sea, from 2007 to 2022, and collected a high-purity all-flavour neutrino sample. The search for a diffuse cosmic neutrino signal using this dataset is presented in this article. This final analysis did not provide a statistically significant observation of the cosmic diffuse flux. However, this is converted into limits on the properties of the cosmic neutrino spectrum. In particular, given the sensitivity of the ANTARES neutrino telescope between 1 and 50 TeV, constraints on single-power-law hypotheses are derived for the cosmic diffuse flux below 20 TeV, especially for power-law fits of the IceCube data with spectral index softer than 2.8.

Searches for Neutrinos in the Direction of Radio-bright Blazars with the ANTARES Telescope

Active galaxies, especially blazars, are among the most promising extragalactic candidates for high-energy neutrino sources. To date, ANTARES searches included these objects and used GeV–TeV γ-ray flux to select blazars. Here, a statistically complete blazar sample selected by their bright radio emission is used as the target for searches of origins of neutrinos collected by the ANTARES neutrino telescope over 13 yr of operation. The hypothesis of a neutrino–blazar directional correlation is tested by pair counting and a complementary likelihood-based approach. The resulting posttrial p-value is 3.0% (2.2σ in the two-sided convention). Additionally, a time-dependent analysis is performed to search for temporal clustering of neutrino candidates as a means of detecting neutrino flares in blazars. None of the investigated sources alone reaches a significant flare detection level. However, the presence of 18 sources with a pretrial significance above 3σ indicates a p = 1.4% (2.5σ in the two-sided convention) detection of a time-variable neutrino flux. An a posteriori investigation reveals an intriguing temporal coincidence of neutrino, radio, and γ-ray flares of the J0242+1101 blazar at a p = 0.5% (2.9σ in the two-sided convention) level. Altogether, the results presented here suggest a possible connection of neutrino candidates detected by the ANTARES telescope with radio-bright blazars.

Studying bioluminescence flashes with the ANTARES deep‐sea neutrino telescope

AbstractWe develop a novel technique to exploit the extensive data sets provided by underwater neutrino telescopes to gain information on bioluminescence in the deep sea. The passive nature of the telescopes gives us the unique opportunity to infer information on bioluminescent organisms without actively interfering with them. We propose a statistical method that allows us to reconstruct the light emission of individual organisms, as well as their location and movement. A mathematical model is built to describe the measurement process of underwater neutrino telescopes and the signal generation of the biological organisms. The Metric Gaussian Variational Inference algorithm is used to reconstruct the model parameters using photon counts recorded by photomultiplier tubes. We apply this method to synthetic data sets and data collected by the ANTARES neutrino telescope. The telescope is located 40 km off the French coast and fixed to the sea floor at a depth of 2475 m. The runs with synthetic data reveal that we can model the emitted bioluminescent flashes of the organisms. Furthermore, we find that the spatial resolution of the localization of light sources highly depends on the configuration of the telescope. Precise measurements of the efficiencies of the detectors and the attenuation length of the water are crucial to reconstruct the light emission. Finally, the application to ANTARES data reveals the first localizations of bioluminescent organisms using neutrino telescope data.

Review of the online analyses of multi-messenger alerts and electromagnetic transient events with the ANTARES neutrino telescope

By constantly monitoring a very large portion of the sky, neutrino telescopes are well-designed to detect neutrinos emitted by transient astrophysical events. Real-time searches with the ANTARES telescope have been performed to look for neutrino candidates coincident with gamma-ray bursts detected by the Swift and Fermi satellites, high-energy neutrino events registered by IceCube, transient events from blazars monitored by HAWC, photon-neutrino coincidences by AMON notices and gravitational wave candidates observed by LIGO/Virgo. By requiring temporal coincidence, this approach increases the sensitivity and the significance of a potential discovery. This paper summarises the results of the follow-up performed of the ANTARES telescope between January 2014 and February 2022, which corresponds to the end of the data-taking period.

Hint for a TeV neutrino emission from the Galactic Ridge with ANTARES

Interactions of cosmic ray protons, atomic nuclei, and electrons in the interstellar medium in the inner part of the Milky Way produce a γ-ray flux from the Galactic Ridge. If the γ-ray emission is dominated by proton and nuclei interactions, a neutrino flux comparable to the γ-ray flux is expected from the same sky region.Data collected by the ANTARES neutrino telescope are used to constrain the neutrino flux from the Galactic Ridge in the 1-100 TeV energy range. Neutrino events reconstructed both as tracks and showers are considered in the analysis and the selection is optimized for the search of an excess in the region |l|<30°, |b|<2°. The expected background in the search region is estimated using an off-zone region with similar sky coverage. Neutrino signal originating from a power-law spectrum with spectral index ranging from Γν=1 to 4 is simulated in both channels. The observed energy distributions are fitted to constrain the neutrino emission from the Ridge.The energy distributions in the signal region are inconsistent with the background expectation at ∼96% confidence level. The mild excess over the background is consistent with a neutrino flux with a power law with a spectral index 2.45−0.34+0.22 and a flux normalization dNνdEν=4.0−2.0+2.7×10−16 GeV−1cm−2s−1sr−1 at 40 TeV reference energy. Such flux is consistent with the expected neutrino signal if the bulk of the observed γ-ray flux from the Galactic Ridge originates from interactions of cosmic ray protons and nuclei with a power-law spectrum extending well into the PeV energy range.

Overview of the results from the ANTARES neutrino telescope

The ANTARES neutrino telescope took high-quality data for over 15 years, starting in 2007 and ending its operations in 2022. During this period, it was the most sensitive detector for cosmic neutrino fluxes from the Southern Sky below 100 TeV, where significant neutrino emissions induced by galactic cosmic rays are expected. In addition, it showed the great potential of under-water neutrino telescopes in various searches involving atmospheric neutrinos and neutrinos from dark matter annihilation and/or decays. This contribution provides an overview of the results achieved over these 15 years and an outlook concerning what is still to come once the analysis of its data will be finalised.

Search for non-standard neutrino interactions with 10 years of ANTARES data

Non-standard interactions of neutrinos arising in many theories beyond the Standard Model can significantly alter matter effects in atmospheric neutrino propagation through the Earth. In this paper, a search for deviations from the prediction of the standard 3-flavour atmospheric neutrino oscillations using the data taken by the ANTARES neutrino telescope is presented. Ten years of atmospheric neutrino data collected from 2007 to 2016, with reconstructed energies in the range from ∼16 GeV to 100 GeV, have been analysed. A log-likelihood ratio test of the dimensionless coefficients εμτ and εττ − εμμ does not provide clear evidence of deviations from standard interactions. For normal neutrino mass ordering, the combined fit of both coefficients yields a value 1.7σ away from the null result. However, the 68% and 95% confidence level intervals for εμτ and εττ − εμμ, respectively, contain the null value. Best fit values, one standard deviation errors and bounds at the 90% confidence level for these coefficients are given for both normal and inverted mass orderings. The constraint on εμτ is among the most stringent to date and it further restrains the strength of possible non-standard interactions in the μ − τ sector.

Search for secluded dark matter towards the Galactic Centre with the ANTARES neutrino telescope

Searches for dark matter (DM) have not provided any solid evidence for the existence of weakly interacting massive particles in the GeV-TeV mass range. Coincidentally, the scale of new physics is being pushed by collider searches well beyond the TeV domain. This situation strongly motivates the exploration of DM masses much larger than a TeV. Secluded scenarios contain a natural way around the unitarity bound on the DM mass, via the early matter domination induced by the mediator of its interactions with the Standard Model. High-energy neutrinos constitute one of the very few direct accesses to energy scales above a few TeV. An indirect search for secluded DM signals has been performed with the ANTARES neutrino telescope using data from 2007 to 2015. Upper limits on the DM annihilation cross section for DM masses up to 6 PeV are presented and discussed.

Search for solar atmospheric neutrinos with the ANTARES neutrino telescope

Solar Atmospheric Neutrinos (SAνs) are produced by the interaction of cosmic rays with the solar medium. The detection of SAνs would provide useful information on the composition of primary cosmic rays as well as the solar density. These neutrinos represent an irreducible source of background for indirect searches for dark matter towards the Sun and the measurement of their flux would allow for a better assessment of the uncertainties related to these searches. In this paper we report on the analysis performed, based on an unbinned likelihood maximisation, to search for SAνs with the ANTARES neutrino telescope. After analysing the data collected over 11 years, no evidence for a solar atmospheric neutrino signal has been found. An upper limit at 90% confidence level on the flux of solar atmospheric neutrinos has been obtained, equal to 7×10-11 [ TeV-1 cm-2 s-1] at E ν = 1 TeV for the reference cosmic ray model assumed.

Search for magnetic monopoles with ten years of the ANTARES neutrino telescope

This work presents a new search for magnetic monopoles using data taken with the ANTARES neutrino telescope over a period of 10 years (January 2008 to December 2017). Compared to previous ANTARES searches, this analysis uses a run-by-run simulation strategy, with a larger exposure as well as a new simulation of magnetic monopoles taking into account the Kasama, Yang and Goldhaber model for their interaction cross-section with matter. No signal compatible with the passage of relativistic magnetic monopoles is observed, and upper limits on the flux of magnetic monopoles with β=v/c≥0.55, are presented. For ultra-relativistic magnetic monopoles the flux limit is ∼7×10−18 cm−2s−1sr−1.

Science with Neutrino Telescopes in Spain

The primary scientific goal of neutrino telescopes is the detection and study of cosmic neutrino signals. However, the range of physics topics that these instruments can tackle is exceedingly wide and diverse. Neutrinos coming from outside the Earth, in association with other messengers, can contribute to clarify the question of the mechanisms that power the astrophysical accelerators which are known to exist from the observation of high-energy cosmic and gamma rays. Cosmic neutrinos can also be used to bring relevant information about the nature of dark matter, to study the intrinsic properties of neutrinos and to look for physics beyond the Standard Model. Likewise, atmospheric neutrinos can be used to study an ample variety of particle physics issues, such as neutrino oscillation phenomena, the determination of the neutrino mass ordering, non-standard neutrino interactions, neutrino decays and a diversity of other physics topics. In this article, we review a selected number of these topics, chosen on the basis of their scientific relevance and the involvement in their study of the Spanish physics community working in the KM3NeT and ANTARES neutrino telescopes.

Indirect Dark Matter search towards the Sun with the ANTARES neutrino telescope

Dark Matter particles, such as Weakly Interactive Massive Particles (WIMPs) gravitationally captured in massive celestial objects, can be indirectly detected through their annihilation into Standard Model particles. The centres of those massive objects are, therefore, places where to look for a possible high energy neutrino flux excess from dark matter annihilations, using neutrino telescopes. The deep-sea neutrino telescope ANTARES, located in the Mediterranean Sea, has been shown to be very competitive in the quest for Dark Matter WIMPs produced in the Galactic Centre. A closer potential DM source is the Sun, where it is possible to have a very clean signal since the background from astrophysical origin is expected to be very low. In this work we show the expected sensitivity of a search for Dark Matter WIMPs from the Sun, using 13 years of data collected by ANTARES.

Search for relativistic magnetic monopoles with ten years of the ANTARES detector data

The presented study is an updated search for Magnetic Monopoles (MMs) using data taken with the ANTARES neutrino telescope over a period of 10 years (January 2008 to December 2017). In accordance with some Grand Unification Theories (GUT), MMs were created during the phase of symmetry breaking in the early Universe, and accelerated by inter-galactic magnetic fields. As a consequence of their high energy, they could cross the Earth and emit a significant signal in a Cherenkov-based telescope like ANTARES, for appropriate mass and velocity ranges. This analysis a new simulation of MMs taking into account the Kasama, Yang and Goldhaber (KYG) model for their cross section with matter. The results obtained for relativistic magnetic monopoles with β = v/c ⩾ 0.817, where v is the magnetic monopole velocity and c the speed of light in vacuum, are presented.

ANTARES search for neutrino flares from the direction of radio-bright blazars

In 2017, a high-energy muon neutrino detected by IceCube was found positionally coincident with the direction of a known blazar, TXS 0506 + 056, in a state of enhanced γ-ray emission. Soon after, IceCube reported compelling evidence for an earlier neutrino flare from the same direction found in the archival data, this time not accompanied by any observed electromagnetic activity. The IceCube findings suggest searching for flaring neutrino emission from astrophysical sources, not necessarily accompanied by flares detected in γ-rays. The analysis presented in this contribution scans the events collected by the ANTARES neutrino telescope in 13 years of data taking in a search for clustering in space and time. The analysis method is based on an unbinned maximum likelihood approach. Generic Gaussian and Box profiles are assumed for the signal time emission, with both the central time and duration of the flare being free parameters in the likelihood maximization. The time-dependent approach is applied to the catalog of radio-bright blazars for which a promising directional correlation with IceCube muon tracks was recently reported [1, 2]. No significant space and time clustering of neutrinos above background expectation is observed after accounting for trials. Seven sources are found to have a pre-trial significance of over 3σ, with the highest excess being the one at the location of the blazar J1500 − 2358, with a pre-trial significance of 3.4σ, corresponding to a post-trial p-value of 40%.

Multi-messenger triggered searches with the ANTARES Neutrino Telescope

The ANTARES neutrino telescope has been operating for thirteen years in the Mediterranean sea with the purpose of searching for high-energy cosmic neutrinos. During the last years, multi-messenger astronomy has become one of the most exciting topics for Cherenkov neutrino detectors, and probably the best strategy to identify the neutrino sources. Thus, the ANTARES Collaboration is actively participating to the follow-up of alerts sent by different experiments, covering the full electromagnetic spectrum and gravitational wave interferometers.ANTARES' real-time response to these alerts is complemented with dedicated offline analyses, the latter being the focus of this talk. These studies allowed to set upper limits that constrain the neutrino emission from various sources, including Fast Radio Bursts, Gamma Ray Bursts and compact binary mergers, as well as neutrino alerts by others neutrino observatories (IceCube, GVD). The latest results are presented here.

Observation of the cosmic ray shadow of the Sun with the ANTARES neutrino telescope

ANTARES is the largest undersea neutrino telescope and it has been taking data in its final configuration for more than ten years. On their journey to the Earth, cosmic rays can be absorbed by celestial objects, like the Sun, leading to a deficit in the atmospheric muon flux measured by the ANTARES detector, the so-called Sun "shadow" effect. This phenomenon can be used to evaluate fundamental telescope characteristics: the detector angular resolution and pointing accuracy. This work describes the study of the Sun "shadow" effect using the ANTARES data collected between 2008 and 2017. The statistical significance of the Sun shadow observation is 3.7σ and the estimated angular resolution value of the ANTARES telescope for downward-going muons is 0.59°±0.10°, which is consistent with the expectations obtained from the Monte Carlo simulations and also with the estimation from the Moon "shadow" analysis of 2007-2016 years. No evidence of systematic pointing shift is found and the resulting pointing accuracy is consistent with the expectations.

Measurement of the atmospheric νe and νμ energy spectra with the ANTARES neutrino telescope

This letter presents a combined measurement of the energy spectra of atmospheric νe and νμ in the energy range between ∼100 GeV and ∼50 TeV with the ANTARES neutrino telescope. The analysis uses 3012 days of detector livetime in the period 2007–2017, and selects 1016 neutrinos interacting in (or close to) the instrumented volume of the detector, yielding shower-like events (mainly from νe+ν‾e charged current plus all neutrino neutral current interactions) and starting track events (mainly from νμ+ν‾μ charged current interactions). The contamination by atmospheric muons in the final sample is suppressed at the level of a few per mill by different steps in the selection analysis, including a Boosted Decision Tree classifier. The distribution of reconstructed events is unfolded in terms of electron and muon neutrino fluxes. The derived energy spectra are compared with previous measurements that, above 100 GeV, are limited to experiments in polar ice and, for νμ, to Super-Kamiokande.

Observation of the cosmic ray shadow of the Sun with the ANTARES neutrino telescope

The ANTARES detector is an undersea neutrino telescope in the Mediterranean Sea. The search for point-like neutrino sources is one of the main goals of the ANTARES telescope, requiring a reliable method to evaluate the detector angular resolution and pointing accuracy. This work describes the study of the Sun "shadow" effect with the ANTARES detector. The shadow is the deficit in the atmospheric muon flux in the direction of the Sun caused by the absorption of the primary cosmic rays. This analysis is based on the data collected between 2008 and 2017 by the ANTARES telescope. The observed statistical significance of the Sun shadow detection is $3.7\sigma$, with an estimated angular resolution of $0.59^\circ\pm0.10^\circ$ for downward-going muons. The pointing accuracy is found to be consistent with the expectations and no evidence of systematic pointing shifts is observed.

Combined search for neutrinos from dark matter self-annihilation in the Galactic Center with ANTARES and IceCube

We present the results of the first combined dark matter search targeting the Galactic Centre using the ANTARES and IceCube neutrino telescopes. For dark matter particles with masses from 50 to 1000 GeV, the sensitivities on the self-annihilation cross section set by ANTARES and IceCube are comparable, making this mass range particularly interesting for a joint analysis. Dark matter self-annihilation through the $\tau^+\tau^-$, $\mu^+\mu^-$, $b\bar{b}$ and $W^+W^-$ channels is considered for both the Navarro-Frenk-White and Burkert halo profiles. In the combination of 2,101.6 days of ANTARES data and 1,007 days of IceCube data, no excess over the expected background is observed. Limits on the thermally-averaged dark matter annihilation cross section $\langle\sigma_A\upsilon\rangle$ are set. These limits present an improvement of up to a factor of two in the studied dark matter mass range with respect to the individual limits published by both collaborations. When considering dark matter particles with a mass of 200 GeV annihilating through the $\tau^+\tau^-$ channel, the value obtained for the limit is $7.44 \times 10^{-24} \text{cm}^{3}\text{s}^{-1}$ for the Navarro-Frenk-White halo profile. For the purpose of this joint analysis, the model parameters and the likelihood are unified, providing a benchmark for forthcoming dark matter searches performed by neutrino telescopes.

ANTARES and IceCube Combined Search for Neutrino Point-like and Extended Sources in the Southern Sky

Abstract A search for point-like and extended sources of cosmic neutrinos using data collected by the ANTARES and IceCube neutrino telescopes is presented. The data set consists of all the track-like and shower-like events pointing in the direction of the Southern Sky included in the nine-year ANTARES point-source analysis, combined with the throughgoing track-like events used in the seven-year IceCube point-source search. The advantageous field of view of ANTARES and the large size of IceCube are exploited to improve the sensitivity in the Southern Sky by a factor of ∼2 compared to both individual analyses. In this work, the Southern Sky is scanned for possible excesses of spatial clustering, and the positions of preselected candidate sources are investigated. In addition, special focus is given to the region around the Galactic Center, whereby a dedicated search at the location of SgrA* is performed, and to the location of the supernova remnant RXJ 1713.7-3946. No significant evidence for cosmic neutrino sources is found, and upper limits on the flux from the various searches are presented.