arXiv subjects

G. Bourlis

Publications and source records attributed to G. Bourlis.

9 recordsLinked to original sources

arXiv2020

Angular reconstruction of high energy air showers using the radio signal spectrum

The Hellenic Open University extensive air shower array (also known as Astroneu array) is a small scale hybrid detection system operating in an area with high levels of electromagnetic noise from anthropogenic activity. In the present study we report the latest results of the data analysis concerning the estimation of the shower direction using the spectrum of the RF system. In a recent layout of the array, 4 RF antennas were operating receiving a common trigger from an autonomous detection station of 3 particle detectors. The directions estimated with the RF system are in very good agreement with the corresponding estimations using the particle detectors demonstrating that a single antenna has the potential for reconstructing the shower axis angular direction.

physics.ins-det↗

arXiv2017

Intrinsic limits on resolutions in muon- and electron-neutrino charged-current events in the KM3NeT/ORCA detector

Studying atmospheric neutrino oscillations in the few-GeV range with a multimegaton detector promises to determine the neutrino mass hierarchy. This is the main science goal pursued by the future KM3NeT/ORCA water Cherenkov detector in the Mediterranean Sea. In this paper, the processes that limit the obtainable resolution in both energy and direction in charged-current neutrino events in the ORCA detector are investigated. These processes include the composition of the hadronic fragmentation products, the subsequent particle propagation and the photon-sampling fraction of the detector. GEANT simulations of neutrino interactions in seawater produced by GENIE are used to study the effects in the 1 - 20 GeV range. It is found that fluctuations in the hadronic cascade in conjunction with the variation of the inelasticity y are most detrimental to the resolutions. The effect of limited photon sampling in the detector is of significantly less importance. These results will therefore also be applicable to similar detectors/media, such as those in ice.

physics.ins-det↗

arXiv2017

Hellenic Open University Reconstruction & Simulation (HOURS) software package: User Guide & short reference of Event Generation, Cherenkov photon production and Optical Module simulation

In this document the simulation part of the Hellenic Open University Reconstruction & Simulation (HOURS) software package is described in detail. HOURS can be used for the generation, simulation, pattern recognition and reconstruction of high energy neutrino produced events in a very large volume neutrino telescope. The objective is to provide as accurate as possible a representation of event properties in a wide range of neutrino telescope configurations and medium optical properties. Moreover, HOURS contains software for the simulation and reconstruction of Extensive Air Showers (EAS) using the HEllenic LYceum Cosmic Observatories Network (HELYCON) scintillation counters. Using the information offered by the simulation/reconstruction of any EAS, and by considering the showers' energetic muons that penetrate the sea to the depth of the neutrino telescope, it is possible to study the joint performance of the neutrino and EAS detectors for physics or calibration purposes. HOURS has been used extensively for the optimization, development of calibration techniques and performance evaluation of the planned Mediterranean neutrino telescope, KM3NeT (km 3 Neutrino Telescope). The results of these studies have been published to various international scientific journals. The code and further information may be found on the HOURS web page: http://physicslab.eap.gr/EN/Simulation_software.html .

astro-ph.IM↗

arXiv2016

Letter of Intent for KM3NeT 2.0

The main objectives of the KM3NeT Collaboration are i) the discovery and subsequent observation of high-energy neutrino sources in the Universe and ii) the determination of the mass hierarchy of neutrinos. These objectives are strongly motivated by two recent important discoveries, namely: 1) The high-energy astrophysical neutrino signal reported by IceCube and 2) the sizable contribution of electron neutrinos to the third neutrino mass eigenstate as reported by Daya Bay, Reno and others. To meet these objectives, the KM3NeT Collaboration plans to build a new Research Infrastructure consisting of a network of deep-sea neutrino telescopes in the Mediterranean Sea. A phased and distributed implementation is pursued which maximises the access to regional funds, the availability of human resources and the synergetic opportunities for the earth and sea sciences community. Three suitable deep-sea sites are identified, namely off-shore Toulon (France), Capo Passero (Italy) and Pylos (Greece). The infrastructure will consist of three so-called building blocks. A building block comprises 115 strings, each string comprises 18 optical modules and each optical module comprises 31 photo-multiplier tubes. Each building block thus constitutes a 3-dimensional array of photo sensors that can be used to detect the Cherenkov light produced by relativistic particles emerging from neutrino interactions. Two building blocks will be configured to fully explore the IceCube signal with different methodology, improved resolution and complementary field of view, including the Galactic plane. One building block will be configured to precisely measure atmospheric neutrino oscillations.

astro-ph.IM↗

arXiv2015

The prototype detection unit of the KM3NeT detector

A prototype detection unit of the KM3NeT deep-sea neutrino telescope has been installed at 3500m depth 80km offshore the Italian coast. KM3NeT in its final configuration will contain several hundreds of detection units. Each detection unit is a mechanical structure anchored to the sea floor, held vertical by a submerged buoy and supporting optical modules for the detection of Cherenkov light emitted by charged secondary particles emerging from neutrino interactions. This prototype string implements three optical modules with 31 photomultiplier tubes each. These optical modules were developed by the KM3NeT Collaboration to enhance the detection capability of neutrino interactions. The prototype detection unit was operated since its deployment in May 2014 until its decommissioning in July 2015. Reconstruction of the particle trajectories from the data requires a nanosecond accuracy in the time calibration. A procedure for relative time calibration of the photomultiplier tubes contained in each optical module is described. This procedure is based on the measured coincidences produced in the sea by the 40K background light and can easily be expanded to a detector with several thousands of optical modules. The time offsets between the different optical modules are obtained using LED nanobeacons mounted inside them. A set of data corresponding to 600 hours of livetime was analysed. The results show good agreement with Monte Carlo simulations of the expected optical background and the signal from atmospheric muons. An almost background-free sample of muons was selected by filtering the time correlated signals on all the three optical modules. The zenith angle of the selected muons was reconstructed with a precision of about 3°.

astro-ph.IM↗

arXiv2014

Deep sea tests of a prototype of the KM3NeT digital optical module

The first prototype of a photo-detection unit of the future KM3NeT neutrino telescope has been deployed in the deep waters of the Mediterranean Sea. This digital optical module has a novel design with a very large photocathode area segmented by the use of 31 three inch photomultiplier tubes. It has been integrated in the ANTARES detector for in-situ testing and validation. This paper reports on the first months of data taking and rate measurements. The analysis results highlight the capabilities of the new module design in terms of background suppression and signal recognition. The directionality of the optical module enables the recognition of multiple Cherenkov photons from the same $^{40}$K decay and the localization bioluminescent activity in the neighbourhood. The single unit can cleanly identify atmospheric muons and provide sensitivity to the muon arrival directions.

astro-ph.IM↗

arXiv2011

Use of floating surface detector stations for the calibration of a deep-sea neutrino telescope

We propose the operation of floating Extensive Air Shower (EAS) detector stations in coincidence with the KM3NeT Mediterranean deep-sea neutrino telescope to determine the absolute position and orientation of the underwater detector and to investigate possible systematic angular errors. We evaluate the accuracy of the proposed calibration strategies using a detailed simulation of the EAS and KM3NeT detectors.

astro-ph.IM↗

arXiv2011

Calibration and Optimization of a Very Large Volume Neutrino Telescope using Extensive Air Showers

We report on a simulation study of the calibration potential offered by floating Extensive Air Shower (EAS) detector stations (HELYCON), operating in coincidence with the KM3NeT Mediterranean deep-sea neutrino telescope. We describe strategies in order to investigate for possible systematic errors in reconstructing the direction of energetic muons as well as to determine the absolute position of the underwater detector.

astro-ph.IM↗

arXiv2009

Probing eV-scale axions with CAST

We have searched for solar axions or other pseudoscalar particles that couple to two photons by using the CERN Axion Solar Telescope (CAST) setup. Whereas we previously have reported results from CAST with evacuated magnet bores (Phase I), setting limits on lower mass axions, here we report results from CAST where the magnet bores were filled with \hefour gas (Phase II) of variable pressure. The introduction of gas generated a refractive photon mass $m_γ$, thereby achieving the maximum possible conversion rate for those axion masses \ma that match $m_γ$. With 160 different pressure settings we have scanned \ma up to about 0.4 eV, taking approximately 2 h of data for each setting. From the absence of excess X-rays when the magnet was pointing to the Sun, we set a typical upper limit on the axion-photon coupling of $\gag\lesssim 2.17\times 10^{-10} {\rm GeV}^{-1}$ at 95% CL for $\ma \lesssim 0.4$ eV, the exact result depending on the pressure setting. The excluded parameter range covers realistic axion models with a Peccei-Quinn scale in the neighborhood of $f_{\rm a}\sim10^{7}$ GeV. Currently in the second part of CAST Phase II, we are searching for axions with masses up to about 1.2 eV using \hethree as a buffer gas.

hep-ex↗