A. Kouchner

Paris Diderot University, Lutetia Parisorum, Île-de-France, France

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Publications (90)248.8 Total impact

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    ABSTRACT: We present the results of searches for point-like sources of neutrinos based on the first combined analysis of data from both the ANTARES and IceCube neutrino telescopes. The combination of both detectors which differ in size and location forms a window in the Southern sky where the sensitivity to point sources improves by up to a factor of two compared to individual analyses. Using data recorded by ANTARES from 2007 to 2012, and by IceCube from 2008 to 2011, we search for sources of neutrino emission both across the Southern sky and from a pre-selected list of candidate objects. No significant excess over background has been found in these searches, and flux upper limits for the candidate sources are presented for $E^{-2.5}$ and $E^{-2}$ power-law spectra with different energy cut-offs.
    Full-text · Article · Nov 2015
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    ABSTRACT: A prototype detection unit of the KM3NeT deep-sea neutrino telescope has been installed at 3500m depth 80km offshore the Italian coast. KM3NeT in its final configuration will contain several hundreds of detection units. Each detection unit is a mechanical structure anchored to the sea floor, held vertical by a submerged buoy and supporting optical modules for the detection of Cherenkov light emitted by charged secondary particles emerging from neutrino interactions. This prototype string implements three optical modules with 31 photomultiplier tubes each. These optical modules were developed by the KM3NeT Collaboration to enhance the detection capability of neutrino interactions. The prototype detection unit was operated since its deployment in May 2014 until its decommissioning in July 2015. Reconstruction of the particle trajectories from the data requires a nanosecond accuracy in the time calibration. A procedure for relative time calibration of the photomultiplier tubes contained in each optical module is described. This procedure is based on the measured coincidences produced in the sea by the 40K background light and can easily be expanded to a detector with several thousands of optical modules. The time offsets between the different optical modules are obtained using LED nanobeacons mounted inside them. A set of data corresponding to 600 hours of livetime was analysed. The results show good agreement with Monte Carlo simulations of the expected optical background and the signal from atmospheric muons. An almost background-free sample of muons was selected by filtering the time correlated signals on all the three optical modules. The zenith angle of the selected muons was reconstructed with a precision of about 3{\deg}.
    Full-text · Article · Oct 2015 · European Physical Journal C
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    J. P. Yañez · A. Kouchner
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    ABSTRACT: Neutrino oscillations have been probed during the last few decades using multiple neutrino sources and experimental set-ups. In the recent years, very large volume neutrino telescopes have started contributing to the field. First ANTARES and then IceCube have relied on large and sparsely instrumented volumes to observe atmospheric neutrinos for combinations of baselines and energies inaccessible to other experiments. Using this advantage, the latest result from IceCube starts approaching the precision of other established technologies, and is paving the way for future detectors, such as ORCA and PINGU. These new projects seek to provide better measurements of neutrino oscillation parameters, and eventually determine the neutrino mass ordering. The results from running experiments and the potential from proposed projects are discussed in this review, emphasizing the experimental challenges involved in the measurements.
    Preview · Article · Sep 2015 · Advances in High Energy Physics
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    ABSTRACT: High-energy neutrinos could be produced in the interaction of charged cosmic rays with matter or radiation surrounding astrophysical sources. Even with the recent detection of extraterrestrial high-energy neutrinos by the IceCube experiment, no astrophysical neutrino source has yet been discovered. Transient sources, such as gamma-ray bursts, core-collapse supernovae, or active galactic nuclei are promising candidates. Multi-messenger programs offer a unique opportunity to detect these transient sources. By combining the information provided by the ANTARES neutrino telescope with information coming from other observatories, the probability of detecting a source is enhanced, allowing the possibility of identifying a neutrino progenitor from a single detected event. A method based on optical and X-ray follow-ups of high-energy neutrino alerts has been developed within the ANTARES collaboration. This program, denoted as TAToO, triggers a network of robotic optical telescopes (TAROT and ROTSE) and the Swift-XRT with a delay of only a few seconds after a neutrino detection, and is therefore well-suited to search for fast transient sources. To identify an optical or X-ray counterpart to a neutrino signal, the images provided by the follow-up observations are analysed with dedicated pipelines. A total of 42 alerts with optical and 7 alerts with X-ray images taken with a maximum delay of 24 hours after the neutrino trigger have been analysed. No optical or X-ray counterparts associated to the neutrino triggers have been found, and upper limits on transient source magnitudes have been derived. The probability to reject the gamma-ray burst origin hypothesis has been computed for each alert.
    Full-text · Article · Aug 2015
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    ABSTRACT: The ANTARES experiment consists of an array of photomultipliers distributed along 12 lines and located deep underwater in the Mediterranean Sea. It searches for astrophysical neutrinos collecting the Cherenkov light induced by the charged particles, mainly muons, produced in neutrino interactions around the detector. Since at energies of $\sim$10 TeV the muon and the incident neutrino are almost collinear, it is possible to use the ANTARES detector as a neutrino telescope and identify a source of neutrinos in the sky starting from a precise reconstruction of the muon trajectory. To get this result, the arrival times of the Cherenkov photons must be accurately measured. A to perform time calibrations with the precision required to have optimal performances of the instrument is described. The reconstructed tracks of the atmospheric muons in the ANTARES detector are used to determine the relative time offsets between photomultipliers. Currently, this method is used to obtain the time calibration constants for photomultipliers on different lines at a precision level of 0.5 ns. It has also been validated for calibrating photomultipliers on the same line, using a system of LEDs and laser light devices.
    Full-text · Article · Jul 2015
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    ABSTRACT: The ANTARES telescope is well-suited for detecting astrophysical transient neutrino sources as it can observe a full hemisphere of the sky at all times with a high duty cycle. The background due to atmospheric particles can be drastically reduced, and the point-source sensitivity improved, by selecting a narrow time window around possible neutrino production periods. Blazars, being radio-loud active galactic nuclei with their jets pointing almost directly towards the observer, are particularly attractive potential neutrino point sources, since they are among the most likely sources of the very high-energy cosmic rays. Neutrinos and gamma rays may be produced in hadronic interactions with the surrounding medium. Moreover, blazars generally show high time variability in their light curves at different wavelengths and on various time scales. This paper presents a time-dependent analysis applied to a selection of flaring gamma-ray blazars observed by the FERMI/LAT experiment and by TeV Cherenkov telescopes using five years of ANTARES data taken from 2008 to 2012. The results are compatible with fluctuations of the background. Upper limits on the neutrino fluence have been produced and compared to the measured gamma-ray spectral energy distribution.
    Full-text · Article · Jun 2015
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    ABSTRACT: A search for high-energy neutrinos coming from the direction of the Galactic Centre is performed using the data recorded by the ANTARES neutrino telescope from 2007 to 2012. The event selection criteria are chosen to maximise the sensitivity to possible signals produced by the self-annihilation of weakly interacting massive particles accumulated around the centre of the Milky Way with respect to the atmospheric background. After data unblinding, the number of neutrinos observed in the line of sight of the Galactic Centre is found to be compatible with background expectations. The 90% C.L. upper limits in terms of the neutrino+anti-neutrino flux, $\rm \Phi_{\nu_{\mu}+\bar{\nu}_\mu}$, and the velocity averaged annihilation cross-section, $\rm <\sigma_{A}v>$, are derived for the WIMP self-annihilation channels into $\rm b\bar{b},W^{+}W^{-},\tau^{+}\tau^{-},\mu^{+}\mu^{-},\nu\bar{\nu}$. The ANTARES limits for $\rm <\sigma_{A}v>$ are shown to be the most stringent for a neutrino telescope over the WIMP masses $\rm 25\,GeV < M_{WIMP} < 10\,TeV$.
    Full-text · Article · May 2015 · Journal of Cosmology and Astroparticle Physics
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    ABSTRACT: The source(s) of the neutrino excess reported by the IceCube Collaboration is unknown. The TANAMI Collaboration recently reported on the multiwavelength emission of six bright, variable blazars which are positionally coincident with two of the most energetic IceCube events. Such objects are prime candidates to be the source of the highest-energy cosmic rays, and thus of associated neutrino emission. We present an analysis of neutrino emission from the six blazars using observations with the ANTARES neutrino telescope. The standard methods of the ANTARES candidate list search are applied to six years of data to search for an excess of muons - and hence their neutrino progenitors - from the directions of the six blazars described by the TANAMI Collaboration, and which are possibly associated with two IceCube events. Monte Carlo simulations of the detector response to both signal and background particle fluxes are used to estimate the sensitivity of this analysis for different possible source neutrino spectra. A maximum-likelihood approach, using the reconstructed energies and arrival directions of through-going muons, is used to identify events with properties consistent with a blazar origin.Both blazars predicted to be the most neutrino-bright in the TANAMI sample (1653-329 and 1714-336) have a signal flux fitted by the likelihood analysis corresponding to approximately one event. This observation is consistent with the blazar-origin hypothesis of the IceCube event IC14 for a broad range of blazar spectra, although an atmospheric origin cannot be excluded. No ANTARES events are observed from any of the other four blazars, including the three associated with IceCube event IC20. This excludes at a 90% confidence level the possibility that this event was produced by these blazars unless the neutrino spectrum is flatter than -2.4.
    Full-text · Article · Mar 2015 · Astronomy and Astrophysics
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    ABSTRACT: Context. The jets of radio-loud Active Galactic Nuclei are among the most powerful particle accelerators in the Universe, and a plausible production site for high-energy cosmic rays. The detection of high-energy neutrinos from these sources would provide unambiguous evidence of a hadronic component in such jets. High-luminosity blazars, such as the flat-spectrum radio quasars (FSRQs), are promising candidates to search for such emission. Because of the low fluxes due to large redshift, these sources are however challenging for the current generation of neutrino telescopes such as ANTARES and IceCube. Aims. This paper proposes to exploit gravitational lensing effects to improve the sensitivity of neutrino telescopes to the intrinsic neutrino emission of distant blazars. Methods. This strategy is illustrated with a search for cosmic neutrinos in the direction of four distant and gravitationally lensed blazars, using data collected from 2007 to 2012 by ANTARES. The magnification factor is estimated for each system assuming a singular isothermal profile for the lens. The neutrino event selection and statistical analysis are identical to the already published ANTARES search for neutrino point sources, which included a few (non-lensed) FSRQs. Results. Based on ANTARES data, we derive upper limits on the intrinsic luminosity of the selected lensed sources. We obtain the strongest constraint from the lensed system B0218$+$357, providing a limit on the total neutrino luminosity of this FSRQ of $1.08\times 10^{46}\,\mathrm{erg}\,\mathrm{s}^{-1}$. This limit is about one order of magnitude lower than those obtained in the ANTARES standard point source search with non-lensed FSRQs, demonstrating the utility of the method.
    Full-text · Article · Nov 2014 · Journal of Cosmology and Astroparticle Physics
  • Antoine Kouchner
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    ABSTRACT: The ANTARES detector, located 40 km off the French coast, is the largest deep-sea neutrino telescope in the world. It consists of an array of 885 photomultipliers detecting the Cherenkov light induced by charged leptons produced by neutrino interactions in and around the detector. The primary goal of ANTARES is to search for astrophysical neutrinos in the TeV-PeV range. This comprises generic searches for any diffuse cosmic neutrino flux as well as more specific searches for astrophysical sources such as active galactic nuclei or galactic sources. The search program also includes multi-messenger analyses based on time and/or space coincidences with other cosmic probes. The ANTARES observatory is sensitive to a wide range of other phenomena, from atmospheric neutrino oscillations to dark matter annihilation or potential exotics such as nuclearites and magnetic monopoles. The most recent results are reported.
    No preview · Article · Oct 2014 · Brazilian Journal of Physics
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    ABSTRACT: The first prototype of a photo-detection unit of the future KM3NeT neutrino telescope has been deployed in the deep waters of the Mediterranean Sea. This digital optical module has a novel design with a very large photocathode area segmented by the use of 31 three inch photomultiplier tubes. It has been integrated in the ANTARES detector for in-situ testing and validation. This paper reports on the first months of data taking and rate measurements. The analysis results highlight the capabilities of the new module design in terms of background suppression and signal recognition. The directionality of the optical module enables the recognition of multiple Cherenkov photons from the same $^{40}$K decay and the localization bioluminescent activity in the neighbourhood. The single unit can cleanly identify atmospheric muons and provide sensitivity to the muon arrival directions.
    Full-text · Article · Sep 2014 · European Physical Journal C
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    Antoine Kouchner
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    ABSTRACT: A short review on the next-generation experiments aiming to study the neutrinos produced in cosmic-ray induced atmospheric showers is presented. The projects currently proposed rely on different complementary detection techniques, from the successful water Cherenkov and magnetized tracko-calorimeter techniques to the more innovative Liquid Argon technology. As all of the proposed detectors must be deeply buried to mitigate the atmospheric muon background, many experiments are expected to be placed deep underground. Following the neutrino telescope approach, the largest ones will be located deep under the sea/ice. Several future projects are part of a wider physics program which includes a neutrino beam. For such cases, the focus is put on the expected performances with only using atmospheric neutrinos. The main physics thread of the review is the question of the determination of the ordering of the neutrino mass eigenstates, referred to as the neutrino mass hierarchy. This falls into the broader context of the precise measurement of the neutrino mixing parameters. The expected reach of the future planned detectors in this respect is also addressed.
    Preview · Article · Sep 2014 · Physics of the Dark Universe
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    ABSTRACT: This paper reports a search for spatial clustering of the arrival directions of high energy muon neutrinos detected by the ANTARES neutrino telescope. An improved two-point correlation method is used to study the autocorrelation of 3058 neutrino candidate events as well as cross-correlations with other classes of astrophysical objects: sources of high energy gamma rays, massive black holes and nearby galaxies. No significant deviations from the isotropic distribution of arrival directions expected from atmospheric backgrounds are observed.
    Full-text · Article · May 2014 · Journal of Cosmology and Astroparticle Physics
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    ABSTRACT: High-frequency internal wave motions of periods down to 20 min have been observed in a yearlong record from the deep Western Mediterranean, mainly in vertical currents. The observations were made using the ANTARES neutrino telescope infrastructure. One line of the telescope is instrumented with environmental monitoring devices, and in particular with an Acoustic Doppler Current Profiler that was used to measure currents around 2,200 m. Such high-frequency internal waves are commonly observed much closer to the sea surface where the vertical density stratification is more stable than in the deep sea. In this paper, they are supported by the relatively large stratification following newly formed dense water. During the severe winters of 2005 and 2006, deep dense-water formation occurred in the Ligurian subbasin. Its collapse and spread over the sea floor across the basin remained detectable for at least 3 years as deduced from the present yearlong current record, which is from 2008. The observed high-frequency internal waves match the occasional density stratification observed in ∼1-m-thin layers using previous shipborne conductivity-temperature-depth measurements. Such layers and waves are relatively unusual in the deep Mediterranean, where commonly several hundreds-of-meters-thick near-homogeneous layers dominate. Such thick near-homogeneous layers provide about a half-decade narrow internal wave band around the inertial frequency (f). In contrast, the presently observed vertical currents occasionally show a "small-scale" internal wave band that is on average 1.5 decades wide, associated with thin-layer stratification. In spite of its relatively large width, this band still shows variance peaking near f rather than near the large-scale buoyancy frequency N (= 2.3-4.5f) and this variance is found to increase with increasing N.
    No preview · Article · Apr 2014
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    ABSTRACT: A search for cosmic neutrino sources using six years of data collected by the ANTARES neutrino telescope has been performed. Clusters of muon neutrinos over the expected atmospheric background have been looked for. No clear signal has been found. The most signal-like accumulation of events is located at equatorial coordinates R.A. = –468 and decl. = –649 and corresponds to a 2.2σ background fluctuation. In addition, upper limits on the flux normalization of an E –2 muon neutrino energy spectrum have been set for 50 pre-selected astrophysical objects. Finally, motivated by an accumulation of seven events relatively close to the Galactic Center in the recently reported neutrino sample of the IceCube telescope, a search for point sources in a broad region around this accumulation has been carried out. No indication of a neutrino signal has been found in the ANTARES data and upper limits on the flux normalization of an E –2 energy spectrum of neutrinos from point sources in that region have been set. The 90% confidence level upper limits on the muon neutrino flux normalization vary between 3.5 and 5.1 × 10–8 GeV cm–2 s–1, depending on the exact location of the source.
    Full-text · Article · Feb 2014 · The Astrophysical Journal
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    ABSTRACT: Results are presented on a search for neutrino emission from a sample of six microquasars, based on the data collected by the ANTARES neutrino telescope between 2007 and 2010. By means of appropriate time cuts, the neutrino search has been restricted to the periods when the acceleration of relativistic jets was taking place at the microquasars under study. The time cuts have been chosen using the information from the X-ray telescopes RXTE/ASM and Swift/BAT, and, in one case, the gamma-ray telescope Fermi/LAT. Since none of the searches has produced a statistically significant signal, upper limits on the neutrino fluences are derived and compared to the predictions from theoretical models.
    Full-text · Article · Feb 2014 · Journal of High Energy Astrophysics
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    ABSTRACT: The reactor neutrino and gallium anomalies can be tested with a 3-4 PBq (75-100 kCi scale) 144Ce-144Pr antineutrino beta-source deployed at the center or next to a large low-background liquid scintillator detector. The antineutrino generator will be produced by the Russian reprocessing plant PA Mayak as early as 2014, transported to Japan, and deployed in the Kamioka Liquid Scintillator Anti-Neutrino Detector (KamLAND) as early as 2015. KamLAND's 13 m diameter target volume provides a suitable environment to measure the energy and position dependence of the detected neutrino flux. A characteristic oscillation pattern would be visible for a baseline of about 10 m or less, providing a very clean signal of neutrino disappearance into a yet-unknown, sterile neutrino state. This will provide a comprehensive test of the electron dissaperance neutrino anomalies and could lead to the discovery of a 4th neutrino state for Delta_m^2 > 0.1 eV^2 and sin^2(2theta) > 0.05.
    Full-text · Article · Dec 2013
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    ABSTRACT: Analysis of the Fermi-LAT data has revealed two extended structures above and below the Galactic Centre emitting gamma rays with a hard spectrum, the so-called Fermi bubbles. Hadronic models attempting to explain the origin of the Fermi bubbles predict the emission of high-energy neutrinos and gamma rays with similar fluxes. The ANTARES detector, a neutrino telescope located in the Mediterranean Sea, has a good visibility to the Fermi bubble regions. Using data collected from 2008 to 2011 no statistically significant excess of events is observed and therefore upper limits on the neutrino flux in TeV range from the Fermi bubbles are derived for various assumed energy cutoffs of the source.
    Full-text · Article · Aug 2013 · European Physical Journal C
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    ABSTRACT: A multimessenger analysis optimized for a correlation of arrival directions of ultra-high energy cosmic rays (UHECRs) and neutrinos is presented and applied to 2190 neutrino candidate events detected in 2007-2008 by the ANTARES telescope and 69 UHECRs observed by the Pierre Auger Observatory between 2004 January 1 and 2009 December 31. No significant correlation is observed. Assuming an equal neutrino flux (E –2 energy spectrum) from all UHECR directions, a 90% CL upper limit on the neutrino flux of 5.0 × 10–8 GeV cm–2 s–1 per source is derived.
    Full-text · Article · Aug 2013 · The Astrophysical Journal
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    ABSTRACT: Atmospheric neutrinos are produced during cascades initiated by the interaction of primary cosmic rays with air nuclei. In this paper, a measurement of the atmospheric \nu_\mu + \bar{\nu}_\mu energy spectrum in the energy range 0.1 - 200 TeV is presented, using data collected by the ANTARES underwater neutrino telescope from 2008 to 2011. Overall, the measured flux is ~25% higher than predicted by the conventional neutrino flux, and compatible with the measurements reported in ice. The flux is compatible with a single power-law dependence with spectral index \gamma_{meas}=3.58\pm 0.12. With the present statistics the contribution of prompt neutrinos cannot be established.
    Full-text · Article · Aug 2013 · European Physical Journal C

Publication Stats

1k Citations
248.80 Total Impact Points

Institutions

  • 2012-2015
    • Paris Diderot University
      • AstroParticule et Cosmologie (APC) UMR 7164
      Lutetia Parisorum, Île-de-France, France
    • Cardiff University
      • School of Physics and Astronomy
      Cardiff, Wales, United Kingdom
  • 2013
    • University of Paris-Est
      La Haye-Descartes, Centre, France
  • 2011-2013
    • French National Centre for Scientific Research
      Lutetia Parisorum, Île-de-France, France
    • AstroParticle and Cosmology Laboratory
      Lutetia Parisorum, Île-de-France, France
    • Leiden University
      Leyden, South Holland, Netherlands
  • 2009-2013
    • Université Paris 13 Nord
      Вильтанез, Île-de-France, France
  • 2005-2011
    • Friedrich-Alexander Universität Erlangen-Nürnberg
      Erlangen, Bavaria, Germany
  • 2007
    • Cea Leti
      Grenoble, Rhône-Alpes, France
  • 2001
    • The University of Sheffield
      • Department of Physics and Astronomy
      Sheffield, England, United Kingdom