H. Asorey

Measurement of the depth of maximum of extensive air showers above 10(18) eV

We describe the measurement of the depth of maximum, Xmax, of the longitudinal development of air showers induced by cosmic rays. Almost four thousand events above 10^18 eV observed by the fluorescence detector of the Pierre Auger Observatory in coincidence with at least one surface detector station are selected for the analysis. The average shower maximum was found to evolve with energy at a rate of (106 +35/-21) g/cm^2/decade below 10^(18.24 +/- 0.05) eV and (24 +/- 3) g/cm^2/decade above this energy. The measured shower-to-shower fluctuations decrease from about 55 to 26 g/cm^2. The interpretation of these results in terms of the cosmic ray mass composition is briefly discussed.

Trigger and aperture of the surface detector array of the Pierre Auger Observatory

The surface detector array of the Pierre Auger Observatory consists of 1600 water-Cherenkov detectors, for the study of extensive air showers (EAS) generated by ultra-high-energy cosmic rays. We describe the trigger hierarchy, from the identification of candidate showers at the level of a single detector, amongst a large background (mainly random single cosmic ray muons), up to the selection of real events and the rejection of random coincidences. Such trigger makes the surface detector array fully efficient for the detection of EAS with energy above 3 x 10(18) eV, for all zenith angles between 0 degrees and 60 degrees, independently of the position of the impact point and of the mass of the primary particle. In these range of energies and angles, the exposure of the surface array can be determined purely on the basis of the geometrical acceptance

A study of the effect of molecular and aerosol conditions in the atmosphere on air fluorescence measurements at the Pierre Auger Observatory

The air fluorescence detector of the Pierre Auger Observatory is designed to perform calorimetric measurements of extensive air showers created by cosmic rays of above 10 eV. To correct these measurements for the effects introduced by atmospheric fluctuations, the Observatory contains a group of monitoring instruments to record atmospheric conditions across the detector site, an area exceeding 3000 km. The atmospheric data are used extensively in the reconstruction of air showers, and are particularly important for the correct determination of shower energies and the depths of shower maxima. This paper contains a summary of the molecular and aerosol conditions measured at the Pierre Auger Observatory since the start of regular operations in 2004, and includes a discussion of the impact of these measurements on air shower reconstructions. Between 10 and 10 eV, the systematic uncertainties due to all atmospheric effects increase from 4% to 8% in measurements of shower energy, and 4 g cm 2 to 8 g cm 2 in measurements of the shower maximum. 2010 Elsevier B.V. All rights reserved.

Cosmic Rays Induced Background Radiation on Board of Commercial Flights

Abstract The aim of this work is to determine the total integrated flux of cosmic radiation which a commercial aircraft is exposed to along specific flight trajectories. To study the radiation background during a flight and its modulation by effects such as altitude, latitude, exposure time and transient magnetospheric events, we perform simulations based on Magnetocosmics and CORSIKA codes, the former designed to calculate the geomagnetic effects on cosmic rays propagation and the latter allows us to simulate the development of extended air showers in the atmosphere. In this first work, by considering the total flux of cosmic rays from 5 GeV to 1 PeV, we obtained the expected integrated flux of secondary particles on board of a commercial airplane during the Bogota-Buenos Aires trip by point-to-point numerical integration.

Implementing the De-thinning Method for High Energy Cosmic Rays Extensive Air Showers Simulations

Abstract To simulate the interaction of cosmic rays with the Earth atmosphere requires highly complex computational resources and several statistical techniques have been developed to simplify those calculations. It is common to implement the thinning algorithms to reduce the number of secondary particles by assigning weights to representative particles in the evolution of the cascade. However, since this is a compression method with information loss, it is required to recover the original flux of secondary particles without introducing artificial biases. In this work we present the preliminary results of our version of the de-thinning algorithm for the reconstruction of thinned simulations of extensive air showers initiated by cosmic rays and photons in the energy range 10 15 E / eV 10 17 .

Preliminary Results From the Latin American Giant Observatory Space Weather Simulation Chain

The Space Weather program of the Latin American Giant Observatory (LAGO) Collaboration was designed to study the variation of the flux of atmospheric secondary particles at ground level produced during the interaction of cosmic rays with the air. This work complements and expands the inference capabilities of the LAGO detection network to identify the influence of solar activity on the particle flux, at places having different geomagnetic rigidity cut-offs and atmospheric depths. This program is developed through a series of Monte Carlo sequential simulations to compute the intensity spectrum of the various components of the radiation field on the ground. A key feature of these calculations is that we performed detailed radiation transport computations as a function of incident direction, time, altitude, as well as latitude and longitude. Magnetic rigidity calculations and corrections for geomagnetic field activity are established by using the MAGNETOCOSMICS code, and the estimation of the flux of secondaries at ground level is implemented by using the CORSIKA code; thus we can examine the local peculiarities in the penumbral regions with a more realistic description of the atmospheric and geomagnetic response in these complex regions of the rigidity space. As an example of our calculation scheme, we report some result on the flux at ground level for two LAGO locations: Bucaramanga-Colombia and San Carlos de Bariloche-Argentina, for the geomagnetically active period of May 2005.

The LAGO Space Weather Program: Directional Geomagnetic Effects, Background Fluence Calculations and Multi-Spectral Data Anal

H. Asorey1,2,3, S. Dasso4,5, L.A. Núñez3,6, Y. Peréz6, C. Sarmiento-Cano∗3, M. Suárez-Durán†3, for The LAGO Collaboration7 1 Laboratorio Detección de Partículas y Radiación, Instituto Balseiro y Centro Atómico Bariloche, S.C. de Bariloche, Argentina. 2 Sede Andina, Universidad Nacional de Río Negro, S.C. de Bariloche, Argentina. 3 Escuela de Física, Universidad Industrial de Santander, Bucaramanga, Colombia. 4 Instituto de Astronomía y Física del Espacio (UBA-CONICET), Buenos Aires, Argentina. 5 Dept. de Ciencias de la Atmósfera y los Océanos and Dept. de Física, Universidad de Buenos Aires, Buenos Aires, Argentina. 6 Centro de Física Fundamental, Dept. de Física, Universidad de Los Andes, Mérida Venezuela 7 lagoproject.org, see the full list of members and institutions at lagoproject.org/collab.html e-mail: lago-pi@lagoproject.org

Analysis of Background Cosmic Ray Rate in the 2010-2012 Period from the LAGO-Chacaltaya Detectors

Bariloche, S.C. de Bariloche, Argentina. 2 Sede Andina, Universidad Nacional de Río Negro, S.C. de Bariloche, Argentina. 3 Escuela de Física, Universidad Industrial de Santander, Bucaramanga, Colombia. 4 Centro de Física Fundamental, Dept. de Física, Universidad de Los Andes, Mérida Venezuela 5 Instituto de Investigaciones Físicas, Universidad Mayor de San Andrés, La Paz, Bolivia 6 lagoproject.org, see the full list of members and institutions at lagoproject.org/collab.html

Astroparticle physics at the Eastern Colombia region

We present the emerging panorama of Astroparticle Physics at the Eastern Colombia region, and describe several ongoing projects, most of them related to the Latin American Giant Observatory (LAGO) Project. This research work is carried out at the Grupo de Investigaciones en Relatividad y Gravitacin of Universidad Industrial de Santander.