36324839
Searches for clustering in the time integrated skymap of the ANTARES neutrino telescope
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.
119249031
Measurement of the atmospheric muon flux with the NEMO Phase-1 detector
Abstract The NEMO Collaboration installed and operated an underwater detector including prototypes of the critical elements of a possible underwater km 3 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 km 3 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.
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.
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.
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.
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.
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.
122074650
A study of the response of thin-oxide MSGCs to minimum ionising particles and low energy X-rays
Abstract Charged particle tracking at LHC requires detector elements with low occupancy and high space and time resolution coupled with sufficient radiation hardness to survive in the harsh environment. We report on progress in the development of MSGCs with thin silicon dioxide substrates and present results of experimental measurements of performance using minimum ionising particle and X-ray beams. The data show that these devices match the performance requirements needed for LHC-type tracking systems.
120592230
A multiterm Boltzmann analysis of drift velocity, diffusion, gain and magnetic-field effects in argon-methane-water-vapour mixtures
Abstract The effect of adding water vapour to argon-methane mixtures used in TPC-type detectors is investigated using the exact multiterm Boltzmann expansion. The transverse and longitudinal diffusion coefficients and the drift velocity are calculated with an accuracy of ± 3, ± 2 and ± 1% respectively. The calculations are extended into the avalanche region and compared to avalanche gain measurements. The effect of misalignment of the electric and magnetic fields on the drift direction is also investigated.
109752350
Operation of thin effective substrate microstrip gas avalanche chambers
Recent advances in Multiwire Proportional Chambers have resulted in the Microstrip Gas Avalanche Chambers (MSGC's). This paper describes recent measurements of the performance of such chambers, fabricated on a Si substrate, in test beam conditions.