ANTARES Neutrino Telescope Research Articles

Model-independent search for neutrino sources with the ANTARES neutrino telescope

A novel method to analyse the spatial distribution of neutrino candidates recorded with the ANTARES neutrino telescope is introduced, searching for an excess of neutrinos in a region of arbitrary size and shape from any direction in the sky. Techniques originating from the domains of machine learning, pattern recognition and image processing are used to purify the sample of neutrino candidates and for the analysis of the obtained skymap. In contrast to a dedicated search for a specific neutrino emission model, this approach is sensitive to a wide range of possible morphologies of potential sources of high-energy neutrino emission. The application of these methods to ANTARES data yields a large-scale excess with a post-trial significance of 2.5σ. Applied to public data from IceCube in its IC40 configuration, an excess consistent with the results from ANTARES is observed with a post-trial significance of 2.1σ.

Measuring the atmospheric neutrino oscillation parameters and constraining the 3+1 neutrino model with ten years of ANTARES data

The ANTARES neutrino telescope has an energy threshold of a few tens of GeV. This allows to study the phenomenon of atmospheric muon neutrino disappearance due to neutrino oscillations. In a similar way, constraints on the 3+1 neutrino model, which foresees the existence of one sterile neutrino, can be inferred. Using data collected by the ANTARES neutrino telescope from 2007 to 2016, a new measurement of Δm322 and θ23 has been performed — which is consistent with world best-fit values — and constraints on the 3+1 neutrino model have been derived.

Combined search for dark matter from the Galactic Centre with the ANTARES and IceCube neutrino telescopes

The ANTARES and IceCube neutrino telescopes have independently searched for neutrinos from dark matter pair-annihilation in the Galactic Centre, and placed limits on the velocity-averaged WIMP annihilation crosssection 〈σν〉. To date, the most stringent limits were obtained by the ANTARES neutrino telescope for WIMP masses > 100 GeV/c2, closely followed by the limits of the IceCube experiment for WIMP masses up to 1 TeV/c2. Here we present the sensitivities of a combined search for dark matter in the Galactic Centre using data from both experiments in a WIMP mass range from 100 GeV/c2 to 1 TeV/c2. This analysis includes IceCube data collected with the complete 86-strings detector from 2012 to 2015 and ANTARES data from 2007 to 2015. The two data sets were combined using a common likelihood framework, and before unblinding the combined sensitivities to 〈σν〉 are shown.

Latest results on high-energy cosmic neutrino searches with the ANTARES neutrino telescope

The ANTARES detector is currently the largest undersea neutrino telescope. Located in the Mediterranean Sea at a depth of 2.5 km, 40 km off the Southern coast of France, it has been looking for cosmic neutrinos for more than 10 years. High-energy cosmic neutrino production is strongly linked with cosmic ray production. The latest results from IceCube Collaboration represent a step forward towards the confirmation of a highenergy cosmic ray source. The ANTARES location in the Northern Hemisphere is optimal for the observation of most of the Galactic Plane, including the Galactic Center. It has constrained the IceCube neutrino excess reports as well as, more recently, the flux from the source identified in the Blazar TXS 0506+056. The latest results of ANTARES on such analyses, including point-like and extended sources, diffuse fluxes, transient phenomena and multi-messenger studies, are presented.

Temporal studies on GRB light curves for neutrino flux predictions in multi-collision zone models

For the analysis here presented, the most luminous GRB detected by Konus-WIND until now was selected, namely GRB 110918A. Through the NeuCosmA code, simulating multi-zone collisions during the GRB prompt emission, a synthetic light curve representative of the observed one has been obtained, in order to study how characteristic parameters of the inner engine activity influence the light curve. This is achieved by varying the input parameters values in the simulation. In agreement with other previous studies, the inner engine is found to be more variable than the observed light curve. Furthermore, the Empirical Mode Decomposition method is applied and its stability is analyzed. Finally, the first multi-collision neutrino flux estimate for a real GRB is presented. Assuming the flux evaluated through the simulation reproducing the GRB gamma-ray light curve and taking into account the data taking conditions and the detector response during the GRB episode, the number of expected signal in the ANTARES neutrino telescope from GRB 110918A was calculated to be µs=6.1×10-4, which is found to be a factor 20 lower than previous estimations with one-zone models.

Recent Results from the Antares Neutrino Telescope

Antares, the first undersea neutrino telescope, has been continuously operating since 2007 in the Mediterranean Sea. The transparency of the water allows for a very good angular resolution in the reconstruction of neutrino events of all flavors. This results in an unmatched sensitivity for neutrino source searches, in a large fraction of the Southern Sky, at TeV energies. As a consequence, Antares provides valuable constraints on the origin of the cosmic neutrino flux discovered by the IceCube Collaboration. Based on an all-flavor dataset spanning nine years of operation of the detector, the latest results of Antares searches for neutrino point sources, and for diffuse neutrino emission from the entire sky as well as from several interesting regions such as the Galactic Plane, are presented. Several results have been obtained through a joint analysis with the IceCube Collaboration. Concerning the multi-messenger program, the focus is made on the follow-up searches of IceCube alerts, in particular the one related to the TXS 0506+056 blazar, thought to be the first extragalactic high-energy neutrino source identified so far.

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.

Latest results of the ANTARES neutrino telescope

Neutrino astronomy is in an exciting moment. The discovery of a cosmic flux of high energy neutrinos by IceCube heralds a new era in which neutrinos have finally joined the multi-messenger study of the Universe. This new important window complements more “traditional” probes (as cosmic rays or photons), given the particular combination of characteristics of neutrinos (neutral, stable and weakly interacting). The ANTARES detector, built in the Mediterranean Sea, has succeeded in two key points. First, it has shown the feasibility of the technique of underwater neutrino telescopes, which offers important advantages in terms of performance (better angular resolution, better visibility of the Galaxy if built in the Northern Hemisphere). This has paved the way for the next step, KM3NeT, already in construction. Second, the physics harvest of ANTARES is very rich, including many results that show the particular advantages of being in the Mediterranean, as mentioned above. The analyses performed include the search for point-like sources, diffuse fluxes, transient phenomena, dark matter, etc. In this talk we will review this long list of achievements.

Simulation studies for large scale acoustic neutrino detectors

The AMADEUS system is a submarine acoustic array that was operated from 2008 until 2015 as a part of the ANTARES neutrino telescope in the Mediterranean Sea. Its design goal was to investigate the feasibility of acoustic neutrino detection in the deep sea. The data taken during its eight years of operation provide a wealth of information for setting up realistic simulations of future acoustic neutrino detectors. Using in addition simulations of neutrino interactions in water, various potential acoustic neutrino detector designs were investigated and methods for suppressing background and reconstructing energy and direction of incoming neutrinos were developed. In this article, some recent results will be presented.

Moon shadow in ANTARES

The ANTARES neutrino telescope is the largest Cherenkov detector currently in operation in Mediterranean sea. The search for point-like neutrino sources is one of the telescope goals. For this reason, both the detector angular resolution and the pointing accuracy need a proper estimation. Measuring the deficit of the atmospheric muons in the direction of the Moon induced by the absorption of primary cosmic rays, the so called Moon shadow, allows to evaluate the pointing performance of the telescope. In this contribution we show the result of the analysis of the data taken between 2007 and 2016. The Moon shadow is detected with 3.5σ significance. This is the first measurement of the ANTARES angular resolution for atmospheric muons and its absolute pointing using a celestial calibration source. The presented results confirm the good pointing performance of the detector as well as the expected angular resolution.

The cosmic ray shadow of the Moon observed with the ANTARES neutrino telescope

One of the main objectives of the ANTARES telescope is the search for point-like neutrino sources. Both the pointing accuracy and the angular resolution of the detector are important in this context and a reliable way to evaluate this performance is needed. In order to measure the pointing accuracy of the detector, one possibility is to study the shadow of the Moon, i.e. the deficit of the atmospheric muon flux from the direction of the Moon induced by the absorption of cosmic rays. Analysing the data taken between 2007 and 2016, the Moon shadow is observed with 3.5sigma statistical significance. The detector angular resolution for downward-going muons is 0.73^{circ }pm 0.14^{circ }. The resulting pointing performance is consistent with the expectations. An independent check of the telescope pointing accuracy is realised with the data collected by a shower array detector onboard of a ship temporarily moving around the ANTARES location.

The search for high-energy neutrinos coincident with fast radio bursts with the ANTARES neutrino telescope

In the past decade, a new class of bright transient radio sources with millisecond duration has been discovered. The origin of these so-called Fast Radio Bursts (FRBs) is still a great mystery despite the growing observational efforts made by various multi-wavelength and multi-messenger facilities. So far, many models have been proposed to explain FRBs but neither the progenitors nor the radiative and the particle acceleration processes at work have been clearly identified. In this paper, the question whether some hadronic processes may occur in the vicinity of the FRB source is assessed. If so, FRBs may contribute to the high energy cosmic-ray and neutrino fluxes. A search for these hadronic signatures has been done using the ANTARES neutrino telescope. The analysis consists in looking for high-energy neutrinos, in the TeV-PeV regime, spatially and temporally coincident with the detected FRBs. Most of the FRBs discovered in the period 2013-2017 were in the field of view of the ANTARES detector, which is sensitive mostly to events originating from the Southern hemisphere. From this period, 12 FRBs have been selected and no coincident neutrino candidate was observed. Upper limits on the per burst neutrino fluence have been derived using a power law spectrum, $\rm{\frac{dN}{dE_\nu}\propto E_\nu^{-\gamma}}$, for the incoming neutrino flux, assuming spectral indexes $\gamma$ = 1.0, 2.0, 2.5. Finally, the neutrino energy has been constrained by computing the total energy radiated in neutrinos assuming different distances for the FRBs. Constraints on the neutrino fluence and on the energy released are derived from the associated null results.

The Search for Neutrinos from TXS 0506+056 with the ANTARES Telescope

Abstract The results of three different searches for neutrino candidates, associated with the IceCube-170922A event or from the direction of TXS 0506+056, by the ANTARES neutrino telescope, are presented. The first search refers to the online follow-up of the IceCube alert; the second is based on the standard time-integrated method employed by the Collaboration to search for point-like neutrino sources; the third uses information from the IceCube time-dependent analysis that reported bursting activity centered on 2014 December 13, as input for an ANTARES time-dependent analysis. The online follow-up and the time-dependent analysis yield no events related to the source. The time-integrated study performed over a period from 2007 to 2017 fits 1.03 signal events, which corresponds to a p-value of 3.4% (not considering trial factors). Only for two other astrophysical objects in our candidate list has a smaller p-value been found. When considering that 107 sources have been investigated, the post-trial p-value for TXS 0506+056 corresponds to 87%.

Long-term monitoring of the ANTARES optical module efficiencies using ^{40}mathrm{{K}} decays in sea water

Cherenkov light induced by radioactive decay products is one of the major sources of background light for deep-sea neutrino telescopes such as ANTARES. These decays are at the same time a powerful calibration source. Using data collected by the ANTARES neutrino telescope from mid 2008 to 2017, the time evolution of the photon detection efficiency of optical modules is studied. A modest loss of only 20% in 9 years is observed. The relative time calibration between adjacent modules is derived as well.

Status of neutrino oscillations 2018: 3σ hint for normal mass ordering and improved CP sensitivity

We present a new global fit of neutrino oscillation parameters within the simplest three-neutrino picture, including new data which appeared since our previous analysis [1]. In this update we include new long-baseline neutrino data involving the antineutrino channel in T2K, as well as new data in the neutrino channel, data from NOνA, as well as new reactor data, such as the Daya Bay 1230 days electron antineutrino disappearance spectrum data and the 1500 live days prompt spectrum from RENO, as well as new Double Chooz data. We also include atmospheric neutrino data from the IceCube DeepCore and ANTARES neutrino telescopes and from Super-Kamiokande. Finally, we also update our solar oscillation analysis by including the 2055-day day/night spectrum from the fourth phase of the Super-Kamiokande experiment. With the new data we find a preference for the atmospheric angle in the upper octant for both neutrino mass orderings, with maximal mixing allowed at Δχ2=1.6(3.2) for normal (inverted) ordering. We also obtain a strong preference for values of the CP phase δ in the range [π,2π], excluding values close to π/2 at more than 4σ. More remarkably, our global analysis shows a hint in favor of the normal mass ordering over the inverted one at more than 3σ. We discuss in detail the status of the mass ordering, CP violation and octant sensitivities, analyzing the interplay among the different neutrino data samples.

An Algorithm for the Reconstruction of Neutrino-induced Showers in the ANTARES Neutrino Telescope

Abstract Muons created by charged current (CC) interactions in the water surrounding the ANTARES neutrino telescope have been almost exclusively used so far in searches for cosmic neutrino sources. Due to their long range, highly energetic muons inducing Cherenkov radiation in the water are reconstructed with dedicated algorithms that allow for the determination of the parent neutrino direction with a median angular resolution of about 0.°4 for an neutrino spectrum. In this paper, an algorithm optimized for accurate reconstruction of energy and direction of shower events in the ANTARES detector is presented. Hadronic showers of electrically charged particles are produced by the disintegration of the nucleus both in CC and neutral current interactions of neutrinos in water. In addition, electromagnetic showers result from the CC interactions of electron neutrinos while the decay of a tau lepton produced in CC interactions will, in most cases, lead to either a hadronic or an electromagnetic shower. A shower can be approximated as a point source of photons. With the presented method, the shower position is reconstructed with a precision of about 1 m; the neutrino direction is reconstructed with a median angular resolution between 2° and 3° in the energy range of 1–1000 TeV. In this energy interval, the uncertainty on the reconstructed neutrino energy is about 5%–10%. The increase in the detector sensitivity due to the use of additional information from shower events in the searches for a cosmic neutrino flux is also presented.

All-sky search for high-energy neutrinos from gravitational wave event GW170104 with the Antares\xa0neutrino telescope

Advanced LIGO detected a significant gravitational wave signal (GW170104) originating from the coalescence of two black holes during the second observation run on January 4th, 2017. An all-sky high-energy neutrino follow-up search has been made using data from the Antares neutrino telescope, including both upgoing and downgoing events in two separate analyses. No neutrino candidates were found within pm 500 s around the GW event time nor any time clustering of events over an extended time window of pm 3 months. The non-detection is used to constrain isotropic-equivalent high-energy neutrino emission from GW170104 to less than sim {1.2}times 10^{{55}} erg for a E^{-2} spectrum. This constraint is valid in the energy range corresponding to the 5–95% quantiles of the neutrino flux [3.2 TeV; 3.6 PeV], if the GW emitter was below the Antares horizon at the alert time.

First all-flavor neutrino pointlike source search with the ANTARES neutrino telescope

A search for cosmic neutrino sources using the data collected with the ANTARES neutrino telescope between early 2007 and the end of 2015 is performed. For the first time, all neutrino interactions --charged and neutral current interactions of all flavours-- are considered in a search for point-like sources with the ANTARES detector. In previous analyses, only muon neutrino charged current interactions were used. This is achieved by using a novel reconstruction algorithm for shower-like events in addition to the standard muon track reconstruction. The shower channel contributes about 23\% of all signal events for an $E^{-2}$ energy spectrum. No significant excess over background is found. The most signal-like cluster of events is located at $(\alpha,\delta) = (343.8^\circ, 23.5^\circ)$ with a significance of $1.9\sigma$. The neutrino flux sensitivity of the search is about $E^2 d\varPhi/dE = 6\cdot10^{-9} GeV cm^{-2} s^{-1}$ for declinations from $-90^\circ$ up to $-42^\circ$, and below $10^{-8} GeV cm^{-2} s^{-1}$ for declinations up to $5^{\circ}$. The directions of 106 source candidates and of 13 muon track events from the IceCube HESE sample are investigated for a possible neutrino signal and upper limits on the signal flux are determined.

Results from the ANTARES Neutrino Telescope

A primary goal of a deep-sea neutrino telescopes as ANTARES is the search for astrophysical neutrinos in the TeV-PeV range. ANTARES is today the largest neutrino telescope in the Northern hemisphere. After the discovery of a cosmic neutrino diffuse flux by the IceCube, the understanding of its origin has become a key mission in high-energy astrophysics. ANTARES makes a valuable contribution for sources located in the Southern sky thanks to its excellent angular resolution in both the muon channel and the cascade channel (induced by all neutrino flavors). Assuming various spectral indexes for the energy spectrum of neutrino emitters, the Southern sky and in particular central regions of our Galaxy are studied searching for point-like objects and for extended regions of emission. In parallel, by adopting a multimessenger approach, based on time and/or space coincidences with other cosmic probes, the sensitivity of such searches can be considerably augmented. ANTARES has participated to a high-energy neutrino follow-up of the gravitational wave signal GW150914, providing the first constraint on high-energy neutrino emission from a binary black hole coalescence. ANTARES has also performed indirect searches for Dark Matter, yielding limits for the spin-dependent WIMP-nucleon cross-section that improve upon those of current direct-detection experiments.

New constraints on all flavor Galactic diffuse neutrino emission with the ANTARES telescope

The flux of very high-energy neutrinos produced in our Galaxy by the interaction of accelerated cosmic rays with the interstellar medium is not yet determined. The characterization of this flux will shed light on Galactic accelerator features, gas distribution morphology and Galactic cosmic ray transport. The central Galactic plane can be the site of an enhanced neutrino production, thus leading to anisotropies in the extraterrestrial neutrino signal as measured by the IceCube Collaboration. The ANTARES neutrino telescope, located in the Mediterranean Sea, offers a favourable view on this part of the sky, thereby allowing for a contribution to the determination of this flux. The expected diffuse Galactic neutrino emission can be obtained linking a model of generation and propagation of cosmic rays with the morphology of the gas distribution in the Milky Way. In this paper, the so-called "Gamma model" introduced recently to explain the high-energy gamma ray diffuse Galactic emission, is assumed as reference. The neutrino flux predicted by the "Gamma model" depends of the assumed primary cosmic ray spectrum cut-off. Considering a radially-dependent diffusion coefficient, this proposed scenario is able to account for the local cosmic ray measurements, as well as for the Galactic gamma ray observations. Nine years of ANTARES data are used in this work to search for a possible Galactic contribution according to this scenario. All flavour neutrino interactions are considered. No excess of events is observed and an upper limit is set on the neutrino flux of $1.1$ ($1.2$) times the prediction of the "Gamma model" assuming the primary cosmic ray spectrum cut-off at 5 (50) PeV. This limit excludes the diffuse Galactic neutrino emission as the major cause of the "spectral anomaly" between the two hemispheres measured by IceCube.