Abstract 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.
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.
In this paper, a time-integrated search for point sources of cosmic neutrinos is presented using the data collected from 2007 to 2010 by the ANTARES neutrino telescope. No statistically significant ...signal has been found and upper limits on the neutrino flux have been obtained. Assuming an E –2 ν spectrum, these flux limits are at 1-10 ×10–8 GeV cm–2 s–1 for declinations ranging from –90° to 40°. Limits for specific models of RX J1713.7–3946 and Vela X, which include information on the source morphology and spectrum, are also given.
The AMADEUS system described in this article is integrated into the ANTARES neutrino telescope in the Mediterranean Sea and aims at the investigation of techniques for acoustic detection of neutrinos ...in the deep sea. Installed at water depths between 2000 and 2400m, its acoustic sensors employ piezo-electric elements for the broad-band recording of signals with frequencies ranging up to 125 kHz with typical sensitivities around −145 dB re. 1V/μPa (including preamplifier). Completed in May 2008, AMADEUS consists of six "acoustic clusters", each comprising six acoustic sensors that are arranged at distances of roughly 1m from each other. Three acoustic clusters each are installed along two vertical mechanical structures (so-called lines) of the ANTARES detector at a horizontal distance of 240m. Vertical spacings within a line range from 15m to 125m. Each cluster contains custom-designed electronics boards to amplify and digitise the acoustic data from the sensors. The data transmission to shore is done via optical fibres, using the TCP/IP protocol. An on-shore computer cluster, currently consisting of four dedicated servers, is used to process, filter and store the selected data. The daily volume of recorded data is about 10 - 20 GByte. The system is operating continuously and automatically, requiring only little human intervention. AMADEUS allows for extensive studies of both transient signals and ambient noise in the deep sea as well as signal correlations on several length scales and localisation of acoustic point sources. Thus the system is excellently suited to assess the background conditions that affect the measurement of bipolar pulses expected to originate from neutrino interactions. This in turn allows for feasibility studies of a future large-scale acoustic neutrino telescope in the Mediterranean Sea.
We report on the investigation of carrier tunneling asymmetry at ferromagnet-semiconductor junctions. By an analytical 2×2 spin model, we show that, when Dresselhaus interactions is included in the ...conduction band of III-V semiconductors (Td or D2d symmetry group), the electrons may undergo a difference of transmission vs. the sign of their incident parallel wavevector normal to the in-plane magnetization. The asymmetry of transmission also exists in the valence band of semiconductors owing to the inner atomic spin-orbit strength and free of asymmetric potentials in bulk or at interfaces. We present advanced multiband 14×14 and 30×30k·p tunneling models together with tunneling transport perturbation calculations based on Green’s function techniques corroborating these results. Those demonstrate that a tunneling spin-current normal to the interface can generate a transverse surface charge current, the so-called Anomalous Tunnel Hall Effect.
The anisotropic properties of thermal transport in insulating or conducting ferromagnets are derived on the basis of the Onsager reciprocity relations applied to a magnetic system. It is shown that ...the angular dependence of the temperature gradient takes the same form as that of the anisotropic magnetoresistance, including anomalous and planar Hall contributions. The measured thermocouple generated between the extremities of the nonmagnetic electrode in thermal contact to the ferromagnet follows this same angular dependence. The sign and amplitude of the magnetovoltaic signal is controlled by the difference of the Seebeck coefficients of the thermocouple.
The chiral tunneling asymmetry for the transmission through a semiconductor interface with spin-orbit coupling (SOC) and antiparallel magnetization is presented from the perspective of the transfer ...Hamiltonian approach. We explicitly show that the expression for the tunneling rate contains terms which are odd in the momentum along the interface thus contributing to the skew tunneling and the transverse current along the interface. These terms contain the scalar chirality that is the mixed vector product of the effective SOC and exchange fields acting on the tunneling electron or hole. The crucial role of the evanescent states in the tunneling asymmetry is revealed. It is shown that the chiral Hall effect also results in a spin injection across the interface. We finally come up with a more general view on the chiral tunneling as a universal phenomenon expected in various systems.
PDF
