120573311
Underwater acoustic positioning system for the SMO and KM3NeT - Italia projects
In the underwater neutrino telescopes, the positions of the Cherenkov light sensors and their movements must be known with an accuracy of few tens of centimetres. In this work, the activities of the SMO and KM3NeT-Italia teams for the development of an acoustic positioning system for KM3NeT-Italia project are presented. The KM3NeT-Italia project foresees the construction, within two years, of 8 towers in the view of the several km3-scale neutrino telescope KM3NeT.
55753733
Measurement of the atmospheric muon depth intensity relation with the NEMO Phase-2 tower
Abstract The results of the analysis of the data collected with the NEMO Phase-2 tower, deployed at 3500 m depth about 80 km off-shore Capo Passero (Italy), are presented. Cerenkov photons detected with the photomultipliers tubes were used to reconstruct the tracks of atmospheric muons. Their zenith-angle distribution was measured and the results compared with Monte Carlo simulations. An evaluation of the systematic effects due to uncertainties on environmental and detector parameters is also included. The associated depth intensity relation was evaluated and compared with previous measurements and theoretical predictions. With the present analysis, the muon depth intensity relation has been measured up to 13 km of water equivalent.
120966174
The NEMO project: A status report
Abstract The latest results and the activities towards the construction of a km 3 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 km 3 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.
119288035
Constraining the neutrino emission of gravitationally lensed Flat-Spectrum Radio Quasars with ANTARES data
This paper proposes to exploit gravitational lensing effects to improve the sensitivity of neutrino telescopes to the intrinsic neutrino emission of distant blazar populations. This strategy is illustrated with a search for cosmic neutrinos in the direction of four distant and gravitationally lensed Flat-Spectrum Radio Quasars. The magnification factor is estimated for each system assuming a singular isothermal profile for the lens. Based on data collected from 2007 to 2012 by the ANTARES neutrino telescope, the strongest constraint is obtained from the lensed quasar B0218+357, providing a limit on the total neutrino luminosity of this source of 1.08 x 10(46) erg s(-1) This limit is about one order of magnitude lower than those previously obtained in the ANTARES standard point source searches with non-lensed Flat-Spectrum Radio Quasars.
110859812
The Central Logic Board and its auxiliary boards for the optical module of the KM3Net detector
The KM3Net neutrino telescope will be composed of many optical modules, each of them containing 31 (3") photomultipliers, connected to a Central Logic Board. The Central Logic Board integrates Time to Digital Converters that measure Time over Threshold of the photomultipliers signals while White Rabbit is used for the optical modules time synchronization. Auxiliary boards have also been designed and built in order to test and extend the performance of the Central Logic Board. The Central Logic Board, as well as the auxiliary boards, will be presented by focusing on the design consideration, prototyping issues and tests.
118473267
A parameterisation of the flux and energy spectrum of single and multiple muons in the deep water or ice
Abstract Atmospheric muons play an important role in underwater/ice neutrino detectors. A parameterisation of the flux of single and multiple muon events, of their lateral distribution and energy spectrum is presented. The kinematics parameters were modelled starting from a full Monte Carlo simulation of the interaction of primary cosmic rays with atmospheric nuclei. The parametric formulas are valid for a vertical depth of 1.5–5 km w.e. and up to 85 ∘ for the zenith angle, and can be used as input for a fast simulation of atmospheric muons in underwater/ice detectors.
120330344
High accuracy measurements of drift time in the streamer mode
Abstract A nitrogen laser focused to a 50 μm spot diameter with a minimum ionising energy deposit was used to scan a streamer tube. Results were obtained for the drift velocity and the spatial resolution. The resolution averaged, σ = ±25 μ m over the total drift length of 8 mm at atmospheric pressure. The charge multiplication region was also observed and could be separated into two regions, a region of low charge multiplication with increased drift velocity and an avalanche region with constant drift time.
121746448
A comparison of the charge division and timing difference techniques in streamer mode
Abstract Resolutions of σ = ±3 mm and non-linearities of less than 5 mm have been measured over 99% of the length of 4 m streamer tubes by timing difference. In comparison charge division measurements give σ = ±1.4 mm at the centre of the tube decreasing to ±3mm at the ends of the tube, with non-linearities less than 5 mm. Both measurements were obtained with 35 m of coaxial cable between the detector and the active electronics.
53630528
Simulation of VUV electroluminescence in micropattern gaseous detectors: the case of GEM and MHSP
Electroluminescence produced during avalanche development in gaseous avalanche detectors is a useful information for triggering, calorimetry and tracking in gaseous detectors. Noble gases present high electroluminescence yields, emitting mainly in the VUV region. The photons can provide signal readout if appropriate photosensors are used. Micropattern gaseous detectors are good candidates for signal amplification in high background and/or low rate experiments due to their high electroluminescence yields and radiopurity. In this work, the VUV light responses of the Gas Electron Multiplier and of the Micro-Hole & Strip Plate, working with pure xenon, are simulated and studied in detail using a new and versatile C++ toolkit. It is shown that the solid angle subtended by a photosensor placed below the microstructures depends on the operating conditions. The obtained absolute EL yields, determined for different gas pressures and as functions of the applied voltage, are compared with those determined experimentally.
121379615
Characterisation of an inhomogeneously irradiated microstrip detector using a fine spot infrared laser
Abstract A prototype silicon microstrip detector with p-strip read-out on oxygen enriched n-type substrate has been non-homogeneously irradiated using a 24 GeV/ c proton beam at the CERN-PS accelerator. The detector has a semicircular shape with radial strip geometry. The peak fluence received by the detector was 4.6×10 14  p/cm 2 though the non-uniform nature of the exposure left part of the detector unirradiated. The inhomogeneous irradiation introduced a damage profile in the detector approximating to that expected in the inner LHC region. High-irradiation gradients are important to study as they can modify the electric field within the silicon. Of special interest are changes in the component of the electric field parallel to the strip plane but perpendicular to the strips, which could lead to systematic shifts in the reconstructed cluster position. If these (flux and position dependent) shifts are sufficiently large they could contribute to degrading the spatial resolution of the detector. In order to quantify these effects, a precision narrow focus light spot from an infrared laser was used to investigate the charge collection properties of the sensor. Particular attention was devoted to the regions where a high gradient of the fluence will have introduced a large gradient in the effective local space charge. The results reported below place limits on the ‘distortions’ due to non-uniform irradiation.
122363641
Observation of kaonic hydrogen atom X-rays
Abstract A special liquid-hydrogen target has been used with a stopping kaon beam in order to search for the X-rays from kaonic hydrogen atoms. A peak at 6.52 ± 0.06 keV, consistent with the unshifted energy of 2p-1s X-rays from K − −p atoms, has been observed with a yield of about 0.1%. The energy shift would imply rather small values for the real K − −p scattering length at threshold.