Search

As part of the R2D2 (Rare Decays with Radial Detector) R &D, the use of a gas detector with a spherical or cylindrical cathode, equipped with a single anode and operating at high pressure, was studied for the search of rare phenomena such as neutrinoless double-beta decay. The presented measurements were obtained with a cylindrical detector, covering gas pressures ranging from 1 to 10 bar in argon and 1 to 6 bar in xenon, using both a point-like source of 210 Po (5.3 MeV α ) and a diffuse source of 222 Rn (5.5 MeV α ). Analysis and interpretation of the data were developed using the anodic current waveform. Similar detection performances were achieved with both gases, and comparable energy resolutions were measured with both sources. As long as the purity of the gas was sufficient, no significant degradation of the measured energy was observed by increasing the pressure. At the highest operating pressure, an energy resolution better than 1.5% full-width at half-maximum (FWHM) was obtained for both gaseous media, although optimal noise conditions were not reached. [ABSTRACT FROM AUTHOR]

The NEMO-3 results for the double- β decay of 150 Nd to the 0 1 + and 2 1 + excited states of 150 Sm are reported. The data recorded during 5.25 year with 36.6 g of the isotope 150 Nd are used in the analysis. The signal of the 2 ν β β transition to the 0 1 + excited state is detected with a statistical significance exceeding 5 σ . The half-life is measured to be T 1 / 2 2 ν β β (0 1 +) = 1. 11 - 0.14 + 0.19 stat - 0.15 + 0.17 syst × 10 20 year, which is the most precise value that has been measured to date. 90% confidence-level limits are set for the other decay modes. For the 2 ν β β decay to the 2 1 + level the limit is T 1 / 2 2 ν β β (2 1 +) > 2.42 × 10 20 year . The limits on the 0 ν β β decay to the 0 1 + and 2 1 + levels of 150 Sm are significantly improved to T 1 / 2 0 ν β β (0 1 +) > 1.36 × 10 22 year and T 1 / 2 0 ν β β (2 1 +) > 1.26 × 10 22 year . [ABSTRACT FROM AUTHOR]

An offline search for a neutrino counterpart to gravitational-wave (GW) events detected during the second observation run (O2) of Advanced-LIGO and Advanced-Virgo performed with ANTARES data is presented. In addition to the search for long tracks induced by ν μ ( ν ¯ μ ) charged current interactions, a search for showering events induced by interactions of neutrinos of any flavour is conducted. The severe spatial and time coincidence provided by the gravitational-wave alert allows regions above the detector horizon to be probed, extending the ANTARES sensitivity over the entire sky. The results of this all-neutrino-flavour and all-sky time dependent analysis are presented. The search for prompt neutrino emission within ±500 s around the time of six GW events yields no neutrino counterparts. Upper limits on the neutrino spectral fluence and constraints on the isotropic energy radiated via high-energy neutrinos (from a few TeV to a few tens of PeV) are set for each GW event analysed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A novel algorithm to reconstruct neutrino-induced particle showers within the ANTARES neutrino telescope is presented. The method achieves a median angular resolution of $$6^\circ $$ for shower energies below 100 TeV. Applying this algorithm to 6 years of data taken with the ANTARES detector, 8 events with reconstructed shower energies above 10 TeV are observed. This is consistent with the expectation of about 5 events from atmospheric backgrounds, but also compatible with diffuse astrophysical flux measurements by the IceCube collaboration, from which 2-4 additional events are expected. A $$90\%$$ C.L. upper limit on the diffuse astrophysical neutrino flux with a value per neutrino flavour of $$\text {E}^2\cdot \Phi ^{90\%} = 4.9 \cdot 10^{-8}\,\mathrm {GeV} \cdot \mathrm {cm^{-2} \cdot s^{-1}\cdot sr^{-1}}$$ is set, applicable to the energy range from 23 TeV to 7.8 PeV, assuming an unbroken $$\text {E}^{-2}$$ spectrum and neutrino flavour equipartition at Earth. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The full data set of the NEMO-3 experiment has been used to measure the half-life of the two-neutrino double beta decay of 100 Mo to the ground state of 100 Ru, T 1 / 2 = 6.81 ± 0.01 stat - 0.40 + 0.38 syst × 10 18 year. The two-electron energy sum, single electron energy spectra and distribution of the angle between the electrons are presented with an unprecedented statistics of 5 × 10 5 events and a signal-to-background ratio of ∼ 80. Clear evidence for the Single State Dominance model is found for this nuclear transition. Limits on Majoron emitting neutrinoless double beta decay modes with spectral indices of n = 2 , 3 , 7 , as well as constraints on Lorentz invariance violation and on the bosonic neutrino contribution to the two-neutrino double beta decay mode are obtained. [ABSTRACT FROM AUTHOR]