Acoustic particle detection is a promising approach for the investigation of ultra-high energy neutrinos. This method utilises the effect that a detectable pressure pulse is generated by the particle shower produced in a neutrino interaction in water at very high energies. The AMADEUS (ANTARES modules for acoustic detection under the sea) system is designed to perform tests of detection techniques and acoustic background studies in the deep sea. The ANTARES neutrino telescope is a water Cherenkov detector completed in May 2008. It is located in the Mediterranean Sea at a water depth of roughly 2500 m. In addition, the detector provides the infrastructure for investigations of the deep sea environment. In this context, acoustic sensors were integrated into the existing infrastructure of the experiment. The AMADEUS setup consists of six clusters comprising six acoustic sensors each. The first three clusters were installed in December 2007 and have been taking data since that time. With the completion of ANTARES the last three clusters were installed. This setup allows position reconstruction of acoustic point sources and to has a dynamic range of about 3 mPa to 10 Pa (RMS) for the frequency range of interest from about 1 kHz to 100 kHz. Preliminary results of the first three clusters will be presented, which are demonstrating the performance of the system.

A search for a diffuse flux of astrophysical muon neutrinos, using data collected by the ANTARES neutrino telescope is presented. A (0.83 x 2 pi) sr sky was monitored for a total of 334 days of equivalent live time. The searched signal corresponds to an excess of events, produced by astrophysical sources, over the expected atmospheric neutrino background. The observed number of events is found compatible with the background expectation. Assuming an E-2 flux spectrum, a 90% c.l. upper limit on the diffuse nu(mu) flux of E-2 Phi(90%) = 5.3 x 10(-8) GeV cm(-2) s(-1) sr(-1) in the energy range 20 TeV-2.5 PeV is obtained. Other signal models with different energy spectra are also tested and some rejected. (C) 2010 Elsevier B.V. All rights reserved.

The latest results and the activities towards the construction of a km3 Cherenkov neutrino detector carried out by the NEMO Collaboration are described. Long-term exploration of a 3500 m deep-sea site close to the Sicilian coast has shown that it is optimal for the installation of the detector. The NEMO Phase-1 project has validated several technologies proposed for the construction of the km3 detector on a test site at 2000 m depth. The new infrastructure on the candidate Capo Passero site set up as part of the Phase-2 project will provide the possibility to test detector components at 3500 m depth.

An algorithm is presented, that provides a fast and robust reconstruction of neutrino induced upward-going muons and a discrimination of these events from downward-going atmospheric muon background in data collected by the ANTARES neutrino telescope. The algorithm consists of a hit merging and hit selection procedure followed by fitting steps for a track hypothesis and a point-like light source. It is particularly well-suited for real time applications such as online monitoring and fast triggering of optical follow-up observations for multi-messenger studies. The performance of the algorithm is evaluated with Monte Carlo simulations and various distributions are compared with that obtained in ANTARES data.

An Acoustic Doppler Current Profiler (ADCP) was moored at the deep-sea site of the ANTARES neutrino telescope near Toulon, France, thus providing a unique opportunity to compare high-resolution acoustic and optical observations between 70 and 170m above the sea bed at 2475m. The ADCP measured downward vertical currents of magnitudes up to 0.03ms−1 in late winter and early spring 2006. In the same period, observations were made of enhanced levels of acoustic reflection, interpreted as suspended particles including zooplankton, by a factor of about 10 and of horizontal currents reaching 0.35ms−1. These observations coincided with high light levels detected by the telescope, interpreted as increased bioluminescence. During winter 2006 deep dense-water formation occurred in the Ligurian subbasin, thus providing a possible explanation for these observations. However, the 10–20 days quasi-periodic episodes of high levels of acoustic reflection, light and large vertical currents continuing into the summer are not direct evidence of this process. It is hypothesized that the main process allowing for suspended material to be moved vertically later in the year is local advection, linked with topographic boundary current instabilities along the rim of the ‘Northern Current’.

The NEMO Collaboration installed and operated an underwater detector including prototypes of the critical elements of a possible underwater km3 neutrino telescope: a four-floor tower (called Mini-Tower) and a Junction Box. The detector was developed to test some of the main systems of the km3 detector, including the data transmission, the power distribution, the timing calibration and the acoustic positioning systems as well as to verify the capabilities of a single tridimensional detection structure to reconstruct muon tracks. We present results of the analysis of the data collected with the NEMO Mini-Tower. The position of photomultiplier tubes (PMTs) is determined through the acoustic position system. Signals detected with PMTs are used to reconstruct the tracks of atmospheric muons. The angular distribution of atmospheric muons was measured and results compared to Monte Carlo simulations.

ANTARES is a high-energy neutrino telescope installed in the Mediterranean Sea at a depth of 2475 m. It consists of a three-dimensional array of optical modules, each containing a large photomultiplier tube. A total of 2700 front-end ASICs named analogue ring samplers (ARS) process the phototube signals, measure their arrival time, amplitude and shape as well as perform monitoring and calibration tasks. The ARS chip processes the analogue signals from the optical modules and converts information into digital data. All the information is transmitted to shore through further multiplexing electronics and an optical link. This paper describes the performance of the ARS chip; results from the functionality and characterization tests in the laboratory are summarized and the long-term performance in the apparatus is illustrated.

The ANTARES high energy neutrino telescope is a three-dimensional array of about 900 photomultipliers distributed over 12 mooring lines installed in the Mediterranean Sea. Between February and November 2007 it acquired data in a 5-line configuration. The zenith angular distribution of the atmospheric muon flux and the associated depth-intensity relation are measured and compared with previous measurements and Monte Carlo expectations. An evaluation of the systematic effects due to uncertainties on environmental and detector parameters is presented.

Abstract. An Acoustic Doppler Current Profiler (ADCP) moored at the deep-sea ANTARES neutrino telescope site near Toulon, France, measured downward vertical currents of amplitudes up to 0.03 m s−1 in spring 2006. The currents were accompanied by enhanced levels of acoustic reflection by a factor of about 10 and by horizontal currents reaching 0.35 m s−1. These observations coincided with high levels of bioluminescence detected by the telescope. Although during winter 2006 deep dense-water formation occurred in this area, episodes of high levels of suspended particles and large vertical currents continuing into the summer are not direct evidence of this process. It is hypothesized that the main process allowing for particles to be moved across the entire water column (2500 m) within a few days, is local convection, triggered by small-mesoscale phenomena, such as meanders including a bipolar vortex, linked with boundary current instabilities.

The selection of the photomultiplier plays a crucial role in the R&D activity related to a large-scale underwater neutrino telescope. This paper illustrates the main procedures and facilities used to characterize the performances of 72 large area photomultipliers, Hamamatsu model R7081 sel. The voltage to achieve a gain of 5×107, dark count rate and single photoelectron time and charge properties of the overall response were measured with a properly attenuated 410 nm pulsed laser. A dedicated study of the spurious pulses was also performed. The results prove that the photomultipliers comply with the general requirements imposed by the project.

A new method for the measurement of the muon flux in the deep-sea ANTARES neutrino telescope and its dependence on the depth is presented. The method is based on the observation of coincidence signals in adjacent storeys of the detector. This yields an energy threshold of about 4GeV. The main sources of optical background are the decay of 40K and the bioluminescence in the sea water. The 40K background is used to calibrate the efficiency of the photo-multiplier tubes.

In this paper we report on the data recorded with the first Antares detector line. The line was deployed on the 14th of February 2006 and was connected to the readout two weeks later. Environmental data for one and a half years of running are shown. Measurements of atmospheric muons from data taken from selected runs during the first six months of operation are presented. Performance figures in terms of time residuals and angular resolution are given. Finally the angular distribution of atmospheric muons is presented and from this the depth profile of the muon intensity is derived.

The latest results and the activities towards the realization of a km3 Cherenkov neutrino detector carried out by the NEMO Collaboration are described. The realization of a Phase-1 project has validated all relevant technologies proposed for the realization of the km3 detector on a test site at 2000m depth. The realization of a new infrastructure on the candidate Capo Passero site (for Phase-2 project) will provide the possibility to test detector components at 3500m depth.

The thesis main topic is the determination of the vertical component of the atmospheric muon flux as a function of the sea depth at the ANTARES site. ANTARES is a Cherenkov neutrino telescope placed at 2500m depth in the Mediterranean Sea at 40 km from the southern cost of France. In order to retrieve back the physical flux from the experimental data a deconvolution algorithm has been perform which takes into consideration the trigger inefficiensies and the reconstruction errors on the zenith angle. The obtained results are in good agreement with other ANTARES indipendent analysis.

The production of high-energy neutrinos is possible in several types of astrophysical sources. The detection of such neutrinos would yield information complementary to that provided by photons and charged particles. This paper presents results from a point source analysis using data taken during 2007 with the five-line partial configuration of the ANTARES neutrino telescope. This search was performed using a binned and an unbinned method. Results are presented both for a list of candidate sources and an all-sky scan. No evidence for any statistically significant ‖ Corresponding author: zornoza@ific.uv.es Search for cosmic neutrino point sources with the 5-line ANTARES telescope 3 neutrino excess has been found. The corresponding upper limits on the cosmic neutrino flux have been determined. Assuming an E spectrum for the sources and for the energy range 3 – 400 TeV, the upper limits at 90% C.L. are E2dφνμ/dE ∼ 3−10×10 −10 TeV cm s, obtained for declinations between −90◦ and 15◦. PACS numbers: 95.55.Vj, 95.85.Ry Search for cosmic neutrino point sources with the 5-line ANTARES telescope 4

The status of the activities towards the realization of a km3 Cherenkov neutrino detector carried out by the NEMO Collaboration is described. The realization of a Phase-1 project, which is under way, will validate the proposed technologies for the realization of the km3 detector on a Test Site at 2000 m depth. The realization of a new infrastructure on the candidate site (Phase-2 project) will provide the possibility to test detector components at 3500 m depth.

The NEMO collaboration proposes to build an underwater neutrino telescope located South-East off the Sicily coast. This paper describes the concepts underlying the communication link design going over the whole data acquisition and transport from the front-end electronics to the module sending data on-shore through a fiber optic link which relies on Dense Wavelength Division Multiplexing. An on-shore board, plugged into a PC, extracts and distributes data both to first-level trigger and control systems. Underwater apparatus monitoring and controls are guaranteed by oceanographic instruments and dedicated sensors, whose data are packed and sent back to shore using the same optical link. The communication is fully bidirectional, allowing transmission of timing and control commands. The architecture described here provides a complete real-time data transport layer between the onshore laboratory and the underwater detector. During winter 2006 a first prototype of the apparatus has been deployed: calibration results from the currently working system are here reported.

Neutrino telescopes will open, in the next years, new opportunities in observational high energy astrophysics. For these experiments, atmospheric muons from primary cosmic ray interactions in the atmosphere play an important role, because they provide the most abundant source of events for calibration and test. On the other side, they represent the major background source. In this paper a fast Monte Carlo generator (called MUPAGE) of bundles of atmospheric muons for underwater/ice neutrino telescopes is presented. MUPAGE is based on parametric formulas [APP25(2006)1] obtained from a full Monte Carlo simulation of cosmic ray showers generating muons in bundle, which are propagated down to 5 km w.e. It produces the event kinematics on the surface of a user-defined virtual cylinder, surrounding the detector. The multiplicity of the muons in the bundle, the muon spatial distribution and energy spectrum are simulated according to a specific model of primary cosmic ray flux, with constraints from measurements of the muon flux with underground experiments. As an example of the application, the result of the generation of events on a cylindrical surface of 3 km^2 at a depth of 2450 m of water is presented.