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Sitarek J.,IFAE | Gaug M.,Autonomous University of Barcelona | Mazin D.,Max Planck Institute for Physics | Paoletti R.,University of Siena | Tescaro D.,Institute of Astrophysics of Canarias
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2013

Recently the readout of the MAGIC telescopes has been upgraded to a new system based on the Domino Ring Sampler version 4 chip. We present the analysis techniques and the signal extraction performance studies of this system. We study the behavior of the baseline, the noise, the cross-talk, the linearity and the time resolution. We investigate also the optimal signal extraction. In addition we show some of the analysis techniques specific to the readout based on the Domino Ring Sampler version 2 chip, previously used in the MAGIC II telescope. © 2013 Elsevier B.V.

Klepser S.,IFAE
Astroparticle Physics | Year: 2012

Astrophysical sources of TeV gamma rays are usually established by Cherenkov telescope observations. These counting type instruments have a field of view of few degrees in diameter and record large numbers of particle air showers via their Cherenkov radiation in the atmosphere. The showers are either induced by gamma rays or diffuse cosmic ray background. The commonly used test statistic to evaluate a possible gamma-ray excess is Li and Ma [6], Eq. (17), which can be applied to independent on- and off-source observations, or scenarios that can be approximated as such. This formula however is unsuitable if the data are taken in so-called "wobble" mode (pointing to several offset positions around the source), if at the same time the acceptance shape is irregular or even depends on operating parameters such as the pointing direction or telescope multiplicity. To provide a robust test statistic in such cases, this paper explores a possible generalization of the likelihood ratio concept on which the formula of Li and Ma is based. In doing so, the multi-pointing nature of the data and the typically known instrument point spread function are fully exploited to derive a new, semi-numerical test statistic. Due to its flexibility and robustness against systematic uncertainties, it is not only useful for detection purposes, but also for skymapping and source shape fitting. Simplified Monte Carlo simulations are presented to verify the results, and several applications and further generalizations of the concept are discussed.© 2012 Elsevier B.V. All rights reserved.

Mazini D.,IFAE
Nuovo Cimento della Societa Italiana di Fisica C | Year: 2012

Ground-based gamma-ray astronomy has had a major breakthrough with the impressive results obtained using systems of imaging atmospheric Cherenkov telescopes. Ground-based gamma-ray astronomy has a huge potential in astrophysics, particle physics and cosmology. CTA is an international initiative to build the next generation instrument, with a factor of 5-10 improvement in sensitivity in the 100 GeV to 10 TeV range and the extension to energies well below 100 GeV and above 100 TeV. CTA will consist of two arrays (one in the Northern hemisphere and one in the Southern hemisphere) for full sky coverage and will be operated as an open observatory. This paper briefly reports on the status and presents the major design concepts of CTA. © Società Italiana di Fisica.

Michela I.,IFAE
Proceedings of the 15th Lomonosov Conference on Elementary Particle Physics: Particle Physics at the Tercentenary of Mikhail Lomonosov | Year: 2013

The T2K experiment studies the phenomenon of neutrinos oscillations as they travel from the Japan Proton Accelerator Research Complex (J-PARC) in Tokai (Japan) to the Super-K detector in the Kamioka Mine, 295 Km away. The aim of the experiment is to measure the mixing angle θ13 using the νe appearance and to improve the atmospheric parameters from the νμ disappearance measurements. The neutrino beam created at J-PARC is monitored by the near detectors site located at 280m downstream of neutrino target. It is split in two parts: the on-axis INGRID detector and the main off-axis detectors ND280. In this article we will briefly describe the setup of near detectors and the analyses finalized in 2010 used as input to the T2K oscillation studies. © 2013 by World Scientific Publishing Co. Pte. Ltd.

Szanecki M.,University of Lodz | Bernlohr K.,Max Planck Institute for Nuclear Physics | Sobczynska D.,University of Lodz | Niedzwiecki A.,University of Lodz | And 2 more authors.
Astroparticle Physics | Year: 2013

We investigate the influence of the geomagnetic field (GF) on the Imaging Air Cherenkov Telescope technique for two northern (Tenerife and San Pedro Martir) and three southern (Salta, Leoncito and Namibia (the H.E.S.S.-site)) site candidates for Cherenkov Telescope Array (CTA) observatories. We use the CORSIKA and sim-telarray programs for Monte Carlo simulations of gamma ray showers, hadronic background and the telescope response. We focus here on gamma ray measurements in the low energy, sub-100 GeV, range. Therefore, we only consider the performance of arrays of several large telescopes. Neglecting the GF effect, we find (in agreement with previous studies) that such arrays have lower energy thresholds, and larger collection areas below 30 GeV, when located at higher altitudes. We point out, however, that in the considered ranges of altitudes and magnetic field intensities, 1800-3600 m a.s.l. and 0-40 μT, respectively, the GF effect has a similar magnitude to this altitude effect. We provide the trigger-level performance parameters of the observatory affected by the GF effect, in particular the collection areas, detection rates and the energy thresholds for all five locations, which information may be useful in the selection of sites for CTA. We also find simple scaling of these parameters with the magnetic field strength, which can be used to assess the magnitude of the GF effect for other sites; in this work we use them to estimate the performance parameters for five sites: South Africa-Beaufort West, USA-Yavapai Ranch, Namibia-Calapanzi, Chile-La Silla and India-Hanle. We roughly investigate the impact of the geophysical conditions on gamma/hadron separation procedures involving image shape and direction cuts. We note that the change of altitude has an opposite effect at the trigger and analysis levels, i.e. gains in triggering efficiency at higher altitudes are partially balanced by losses in the separation efficiency. In turn, a stronger GF spoils both the shape and the direction discrimination of gamma rays, thus its effects at the trigger and analysis levels add up resulting in a significant reduction of the observatory performance. Overall, our results indicate that the local GF strength at a site can be equally important as its altitude for the low-energy performance of CTA. © 2013 Elsevier B.V. All rights reserved.

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