110 research outputs found
Neutrino-induced showers in the ANTARES deep-sea telescope
No full textReconstruction of neutrino-induced showers, initiated by neutral-current interactions, can extend the sensitivity of the ANTARES detector to all neutrino flavors. A major challenge in reconstructing showers is their selection from an overwhelming background of down-going atmospheric muons. We have developed a shower selection strategy in order to select up-going showers with high efficiency and purity. We have tuned the selection strategy on Monte-Carlo simulations containing the proper amount of background and atmospheric neutrino-induced showers. The obtained results indicate an efficiency of 21% with a purity better than 90% for the shower selection. We applied the selection strategy to ANTARES experimental data and observed a satisfactory performance of the discriminating variables. (C) 2012 Elsevier B.V. All rights reserved
Performance of photo-sensors for KM3NeT
No full text<p>The future deep-sea neutrino telescope of multi cubic-km size, KM3NeT, has been designed for an efficient search for high energy neutrinos originating from galactic and extragalactic sources. The detection principle relies on the measurement of Cherenkov light emitted from relativistic charged secondary particles caused by the interaction of neutrinos with matter inside or surrounding the active detection volume. In order to provide a homogeneous photon acceptance and to reduce the environmental background by local coincidences between neighbouring photo sensors, a digital optical module (DOM) containing an array of 31 3-in, diameter photomultiplier tubes (PMTs) has been designed. Optimum performance requires sensitivity to single-photo electrons, high collection efficiency at low dark noise, homogeneous photo-cathode response and excellent timing properties. We have studied the response to single photo electrons of a newly developed 3-in. diameter PMT from ET Enterprises Ltd. A 2D-scanning system with a picosecond laser illuminating various positions on the photo-cathode surface was employed to study the timing and homogeneity of the PMT. Results of these investigations indicate good photo-cathode homogeneity, low dark noise on the sub-kHz level, and an average transit-time spread below 2 ns. Simulations indicate a significantly improved signal-to-background ratio in the multi-PMT DOM as compared to a triplet of optical modules each housing a single 10-in. PMT. (C) 2012 Elsevier B.V. All rights reserved.</p>
Multi-PMT optical module for the KM3NeT neutrino telescope
No full textThe future cubic kilometre scale neutrino telescope KM3NeT will employ a novel type of a Digital Optical Module (DOM), developed during the recent FP6 Design Study. A pressure-resistant glass sphere hosts 31 photomultiplier tubes (PMTs) of 3-in, diameter, together with all the electronics for high-voltage generation and signal readout. The optical module forms a complete stand-alone detector that. is connected to the outside world via a single optical fibre and two copper conductors providing electrical power. The advantages of using multiple small PMTs in the same DOM are the higher quantum efficiency (>30% expected), smaller transit time spread, better two-photon separation capability and directional sensitivity. Moreover, a longer operating lifetime is expected than for large PMTs due to the accumulation of less charge on the anode. In addition, small PMTs are insensitive to the Earth's magnetic field and do not require mu-metal shielding. In order to maximise the detector sensitivity, each PMT will be surrounded by an expansion cone collecting photons that would normally miss the photocathode. Such an expansion cone consists of an aluminium ring filled with silicone gel. An increase in the overall sensitivity, integrated over all angles of incidence, was estimated to be about 27%. Monte-Carlo simulations have shown that a detector configuration with multi-PMT DOMs requires three times less OMs to achieve the same performance as conventional OMs hosting 10-in. PMTs. Prototype DOMs are currently being built by the KM3NeT consortium. (C) 2011 Elsevier B.V. All rights reserved
Photo-sensors for a Multi-PMT optical module in KM3NeT
No full textA deep-sea Neutrino Telescope of at least 1 km(3) size (KM3NeT) is being designed to search for high-energy (1-1000 TeV) neutrinos originating from galactic and extragalactic sources. The detection principle exploits the measurement of Cherenkov light emitted by charged particles resulting from neutrino interactions in the matter surrounding the telescope. An optical module containing an array of 31 3-in, diameter photomultiplier tubes is a promising alternative to an optical module containing one 10-in, diameter phototube. The single photo-electron response of 3-in. diameter phototubes (Photonis XP53B20 and ETEL 9822B) has been investigated. Phototube characteristics such as the collection efficiency, transit-time spread and peak-to-valley ratio were determined at various positions across the photocathode surface in a remote-controlled 2D scanning system. Results of these investigations are reported and the perspectives to employ the investigated phototube types in the Multi-PMT optical module of the future KM3NeT detector are discussed. (C) 2010 Elsevier B.V. All rights reserved
The multi-PMT optical module for KM3NeT
No full textIn the future neutrino telescope KM3NeT a novel type of optical module (OM) will be employed to optimize the sensitivity to Cherenkov photons and maximize the environmental background suppression. The multiPMT OM, a pressure-resistant glass sphere containing 31 photomultiplier tubes (PMTs) of 3-in. diameter, has been developed and prototyped including electronics for high-voltage generation, signal digitization and optical signal transmission. Monte-Carlo simulations show that a multi-PMT OM configuration requires three times less OMs to achieve the same performance as conventional OMs hosting 10-in. PMTs. (C) 2012 Elsevier B.V. All rights reserved
Evidence for a mixed mass composition at the ‘ankle’ in the cosmic-ray spectrum
No full textWe report a first measurement for ultrahigh energy cosmic rays of the correlation between the depth of shower maximum and the signal in the water Cherenkov stations of air-showers registered simultaneously by the fluorescence and the surface detectors of the Pierre Auger Observatory. Such a correlation measurement is a unique feature of a hybrid air-shower observatory with sensitivity to both the electromagnetic and muonic components. It allows an accurate determination of the spread of primary masses in the cosmic-ray flux. Up till now, constraints on the spread of primary masses have been dominated by systematic uncertainties. The present correlation measurement is not affected by systematics in the measurement of the depth of shower maximum or the signal in the water Cherenkov stations. The analysis relies on general characteristics of air showers and is thus robust also with respect to uncertainties in hadronic event generators. The observed correlation in the energy range around the ‘ankle’ at lg(E/eV)=18.5–19.0lg(E/eV)=18.5–19.0 differs significantly from expectations for pure primary cosmic-ray compositions. A light composition made up of proton and helium only is equally inconsistent with observations. The data are explained well by a mixed composition including nuclei with mass A>4A>4. Scenarios such as the proton dip model, with almost pure compositions, are thus disfavored as the sole explanation of the ultrahigh-energy cosmic-ray flux at Earth
The IceCube Neutrino Observatory, the Pierre Auger Observatory and the Telescope Array: Joint Contribution to the 34th International Cosmic Ray Conference (ICRC 2015)
No full textWe have conducted three searches for correlations between ultra-high energy cosmic rays detected by the Telescope Array and the Pierre Auger Observatory, and high-energy neutrino candidate events from IceCube. Two cross-correlation analyses with UHECRs are done: one with 39 cascades from the IceCube `high-energy starting events' sample and the other with 16 high-energy `track events'. The angular separation between the arrival directions of neutrinos and UHECRs is scanned over. The same events are also used in a separate search using a maximum likelihood approach, after the neutrino arrival directions are stacked. To estimate the significance we assume UHECR magnetic deflections to be inversely proportional to their energy, with values , and at 100 EeV to allow for the uncertainties on the magnetic field strength and UHECR charge. A similar analysis is performed on stacked UHECR arrival directions and the IceCube sample of through-going muon track events which were optimized for neutrino point-source searches
Measurement of the circular polarization in radio emission from extensive air showers confirms emission mechanisms
No full textContains fulltext :
162184pub.pdf (Publisher’s version ) (Open Access)
Contains fulltext :
162184.pdf (Author’s version preprint ) (Open Access)7 p
- …
