The Optical System for the Large Size Telescope of the Cherenkov Telescope Array

The Large Size Telescope (LST) of the Cherenkov Telescope Array (CTA) is designed to achieve a threshold energy of 20 GeV. The LST optics is composed of one parabolic primary mirror 23 m in diameter and 28 m focal length. The reflector dish is segmented in 198 hexagonal, 1.51 m flat to flat mirrors. The total effective reflective area, taking into account the shadow of the mechanical structure, is about 368 m$^2$. The mirrors have a sandwich structure consisting of a glass sheet of 2.7 mm thickness, aluminum honeycomb of 60 mm thickness, and another glass sheet on the rear, and have a total weight about 47 kg. The mirror surface is produced using a sputtering deposition technique to apply a 5-layer coating, and the mirrors reach a reflectivity of $\sim$94% at peak. The mirror facets are actively aligned during operations by an active mirror control system, using actuators, CMOS cameras and a reference laser. Each mirror facet carries a CMOS camera, which measures the position of the light spot of the optical axis reference laser on the target of the telescope camera. The two actuators and the universal joint of each mirror facet are respectively fixed to three neighboring joints of the dish space frame, via specially designed interface plate.Comment: In Proceedings of the 34th International Cosmic Ray Conference (ICRC2015), The Hague, The Netherlands. All CTA contributions at arXiv:1508.0589

Search for Anisotropy of Ultra-High Energy Cosmic Rays with the Telescope Array Experiment

We study the anisotropy of Ultra-High Energy Cosmic Ray (UHECR) events collected by the Telescope Array (TA) detector in the first 40 months of operation. Following earlier studies, we examine event sets with energy thresholds of 10 EeV, 40 EeV, and 57 EeV. We find that the distributions of the events in right ascension and declination are compatible with an isotropic distribution in all three sets. We then compare with previously reported clustering of the UHECR events at small angular scales. No significant clustering is found in the TA data. We then check the events with E>57 EeV for correlations with nearby active galactic nuclei. No significant correlation is found. Finally, we examine all three sets for correlations with the large-scale structure of the Universe. We find that the two higher-energy sets are compatible with both an isotropic distribution and the hypothesis that UHECR sources follow the matter distribution of the Universe (the LSS hypothesis), while the event set with E>10 EeV is compatible with isotropy and is not compatible with the LSS hypothesis at 95% CL unless large deflection angles are also assumed. We show that accounting for UHECR deflections in a realistic model of the Galactic magnetic field can make this set compatible with the LSS hypothesis.Comment: 10 pages, 9 figure

The Cherenkov Telescope Array Large Size Telescope

The two arrays of the Very High Energy gamma-ray observatory Cherenkov Telescope Array (CTA) will include four Large Size Telescopes (LSTs) each with a 23 m diameter dish and 28 m focal distance. These telescopes will enable CTA to achieve a low-energy threshold of 20 GeV, which is critical for important studies in astrophysics, astroparticle physics and cosmology. This work presents the key specifications and performance of the current LST design in the light of the CTA scientific objectives.Comment: 4 pages, 5 figures, In Proceedings of the 33rd International Cosmic Ray Conference (ICRC2013), Rio de Janeiro (Brazil). All CTA contributions at arXiv:1307.223

Mirror development for the Cherenkov Telescope Array

The Cherenkov Telescope Array (CTA) is a planned observatory for very-high energy gamma-ray astronomy. It will consist of several tens of telescopes of different sizes, with a total mirror area of up to 10,000 square meters. Most mirrors of current installations are either polished glass mirrors or diamond-turned aluminium mirrors, both labour intensive technologies. For CTA, several new technologies for a fast and cost-efficient production of light-weight and reliable mirror substrates have been developed and industrial pre-production has started for most of them. In addition, new or improved aluminium-based and dielectric surface coatings have been developed to increase the reflectance over the lifetime of the mirrors compared to those of current Cherenkov telescope instruments.Fil: Forster, A.. Max-Planck-Institut fur Kernphysik; AlemaniaFil: Armstrong, T.. Durham University; Reino UnidoFil: Baba, H.. Ibaraki University; JapónFil: Bähr, J.. No especifíca;Fil: Bonardi, A.. Universitat Tübingen; AlemaniaFil: Bonnoli, G.. Osservatorio Astronomico di Brera; ItaliaFil: Brun, P.. No especifíca;Fil: Canestrari, R.. Osservatorio Astronomico di Brera; ItaliaFil: Chadwick, P.. Durham University; Reino UnidoFil: Chikawa, M.. University of Tokyo; JapónFil: Carton, P.-H.. Centre de Saclay; FranciaFil: De Souza, V.. Universidade de Sao Paulo; BrasilFil: Dipold, J.. Universidade de Sao Paulo; BrasilFil: Doro, M.. Università di Padova; ItaliaFil: Durand, D.. No especifíca;Fil: Dyrda, M.. Polish Academy of Sciences; ArgentinaFil: Giro, E.. Osservatorio Astronomico di Padova; ItaliaFil: Glicenstein, J.-F.. No especifíca;Fil: Hanabata, Y.. Kinki University; JapónFil: Hayashida, M.. University of Tokyo; JapónFil: Hrabovski, M.. No especifíca;Fil: Jeanney, C.. Centre de Saclay; FranciaFil: Kagaya, M.. Ibaraki University; JapónFil: Katagiri, H.. Ibaraki University; JapónFil: Lessio, L.. Osservatorio Astronomico di Padova; ItaliaFil: Mandat, D.. Institute of Physics of the Academy of Sciences of the Czech Republic; República ChecaFil: Mariotti, M.. Università di Padova; ItaliaFil: Medina, Maria Clementina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: Yoshida, T.. Ibaraki University; Japón33rd International Cosmic Ray ConferenceRío de JaneiroBrasilBrazilian Physical Societ

Charged-Particle Multiplicities in Charged-Current Neutrino-- and Anti-Neutrino--Nucleus Interactions

The CHORUS experiment, designed to search for $\nu_{\mu}\to\nu_{\tau}$ oscillations, consists of a nuclear emulsion target and electronic detectors. In this paper, results on the production of charged particles in a small sample of charged-current neutrino-- and anti-neutrino--nucleus interactions at high energy are presented. For each event, the emission angle and the ionization features of the charged particles produced in the interaction are recorded, while the standard kinematic variables are reconstructed using the electronic detectors. The average multiplicities for charged tracks, the pseudo-rapidity distributions, the dispersion in the multiplicity of charged particles and the KNO scaling are studied in different kinematical regions. A study of quasi-elastic topologies performed for the first time in nuclear emulsions is also reported. The results are presented in a form suitable for use in the validation of Monte Carlo generators of neutrino--nucleus interactions.Comment: 17 pages, 5 figure

Leading order analysis of neutrino induced dimuon events in the CHORUS experiment

We present a leading order QCD analysis of a sample of neutrino induced charged-current events with two muons in the final state originating in the lead-scintillating fibre calorimeter of the CHORUS detector. The results are based on a sample of 8910 neutrino and 430 antineutrino induced opposite-sign dimuon events collected during the exposure of the detector to the CERN Wide Band Neutrino Beam between 1995 and 1998. % with $E_{\mu 1},E_{\mu 2} > 5$ GeV and $Q^2 > 3$ GeV$^2$ collected %between 1995 and 1998. The analysis yields a value of the charm quark mass of \mc = (1.26\pm 0.16 \pm 0.09) \GeVcc and a value of the ratio of the strange to non-strange sea in the nucleon of $\kappa = 0.33 \pm 0.05 \pm 0.05$, improving the results obtained in similar analyses by previous experiments.Comment: Submitted to Nuclear Physics

Associated Charm Production in Neutrino-Nucleus Interactions

In this paper a search for associated charm production both in neutral and charged current $\nu$-nucleus interactions is presented. The improvement of automatic scanning systems in the {CHORUS} experiment allows an efficient search to be performed in emulsion for short-lived particles. Hence a search for rare processes, like the associated charm production, becomes possible through the observation of the double charm-decay topology with a very low background. About 130,000 $\nu$ interactions located in the emulsion target have been analysed. Three events with two charm decays have been observed in the neutral-current sample with an estimated background of 0.18$\pm$0.05. The relative rate of the associated charm cross-section in deep inelastic $\nu$ interactions, $\sigma(c\bar{c}\nu)/\sigma_\mathrm{NC}^\mathrm{DIS}= (3.62^{+2.95}_{-2.42}({stat})\pm 0.54({syst}))\times 10^{-3}$ has been measured. One event with two charm decays has been observed in charged-current $\nu_\mu$ interactions with an estimated background of 0.18$\pm$0.06 and the upper limit on associated charm production in charged-current interactions at 90% C.L. has been found to be $\sigma (c\bar{c} \mu^-)/\sigma_\mathrm{CC} < 9.69 \times 10^{-4}$.Comment: 10 pages, 4 figure