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. (C) 2009 Elsevier B.V. All rights reserved.

Atmospheric effects on extensive air showers observed with the surface detector of the Pierre Auger observatory

Atmospheric parameters, Such as pressure (P), temperature (T) and density (rho proportional to P/T), affect the development of extensive air showers initiated by energetic cosmic rays. We have Studied the impact of atmospheric variations on extensive air showers by means of the surface detector of the Pierre Auger Observatory. The rate of events shows a similar to 10% seasonal modulation and similar to 2% diurnal one. We find that the observed behaviour is explained by a model including the effects associated with the variations of P and rho. The former affects the longitudinal development of air showers while the latter influences the Moliere radius and hence the lateral distribution of the shower particles. The model is validated with full simulations of extensive air showers using atmospheric profiles measured at the site of the Pierre Auger Observatory. (C) 2009 Elsevier B.V. All rights reserved.

Upper limit on the cosmic-ray photon fraction at EeV energies from the Pierre Auger Observatory

From direct observations of the longitudinal development of ultra-high energy air showers performed with the Pierre Auger Observatory, upper limits of 3.8%, 2.4%, 3.5% and 11.7% (at 95% c.l.) are obtained on the fraction of cosmic-ray photons above 2, 3, 5 and 10 EeV (1 EeV equivalent to 10(18) eV), respectively. These are the first experimental limits on ultra-high energy photons at energies below 10 EeV. The results complement previous constraints on top-down models from array data and they reduce systematic uncertainties in the interpretation of shower data in terms of primary flux, nuclear composition and proton-air cross-section. (C) 2009 Elsevier B.V. All rights reserved.

Anisotropy and chemical composition of ultra-high energy cosmic rays using arrival directions measured by the Pierre Auger Observatory

The Pierre Auger Collaboration has reported. evidence for anisotropy in the distribution of arrival directions of the cosmic rays with energies E > E(th) = 5.5 x 10(19) eV. These show a correlation with the distribution of nearby extragalactic objects, including an apparent excess around the direction of Centaurus A. If the particles responsible for these excesses at E > E(th) are heavy nuclei with charge Z, the proton component of the sources should lead to excesses in the same regions at energies E/Z. We here report the lack of anisotropies in these directions at energies above E(th)/Z (for illustrative values of Z = 6, 13, 26). If the anisotropies above E(th) are due to nuclei with charge Z, and under reasonable assumptions about the acceleration process, these observations imply stringent constraints on the allowed proton fraction at the lower energies.

Search for first harmonic modulation in the right ascension distribution of cosmic rays detected at the Pierre Auger Observatory

We present the results of searches for dipolar-type anisotropies in different energy ranges above 2.5 x 10(17) eV with the surface detector array of the Pierre Auger Observatory, reporting on both the phase and the amplitude measurements of the first harmonic modulation in the right-ascension distribution. Upper limits on the amplitudes are obtained, which provide the most stringent bounds at present, being below 2% at 99% C.L. for EeV energies. We also compare our results to those of previous experiments as well as with some theoretical expectations. (C) 2011 Elsevier B.V. All rights reserved.

The Pierre Auger Observatory scaler mode for the study of solar activity modulation of galactic cosmic rays

Since data-taking began in January 2004, the Pierre Auger Observatory has been recording the count rates of low energy secondary cosmic ray particles for the self-calibration of the ground detectors of its surface detector array. After correcting for atmospheric effects, modulations of galactic cosmic rays due to solar activity and transient events are observed. Temporal variations related with the activity of the heliosphere can be determined with high accuracy due to the high total count rates. In this study, the available data are presented together with an analysis focused on the observation of Forbush decreases, where a strong correlation with neutron monitor data is found.

The exposure of the hybrid detector of the Pierre Auger Observatory

The Pierre Auger Observatory is a detector for ultra-high energy cosmic rays. It consists of a surface array to measure secondary particles at ground level and a fluorescence detector to measure the development of air showers in the atmosphere above the array. The ""hybrid"" detection mode combines the information from the two subsystems. We describe the determination of the hybrid exposure for events observed by the fluorescence telescopes in coincidence with at least one water-Cherenkov detector of the surface array. A detailed knowledge of the time dependence of the detection operations is crucial for an accurate evaluation of the exposure. We discuss the relevance of monitoring data collected during operations, such as the status of the fluorescence detector, background light and atmospheric conditions, that are used in both simulation and reconstruction. (C) 2010 Elsevier B.V. All rights reserved.

The fluorescence detector of the Pierre Auger Observatory

The Pierre Auger Observatory is a hybrid detector for ultra-high energy cosmic rays. It combines a surface array to measure secondary particles at ground level together with a fluorescence detector to measure the development of air showers in the atmosphere above the array. The fluorescence detector comprises 24 large telescopes specialized for measuring the nitrogen fluorescence caused by charged particles of cosmic ray air showers. In this paper we describe the components of the fluorescence detector including its optical system, the design of the camera, the electronics, and the systems for relative and absolute calibration. We also discuss the operation and the monitoring of the detector. Finally, we evaluate the detector performance and precision of shower reconstructions. (C) 2010 Elsevier B.V All rights reserved.

Measurement of the energy spectrum of cosmic rays above 10(18) eV using the Pierre Auger Observatory

We report a measurement of the flux of cosmic rays with unprecedented precision and Statistics using the Pierre Auger Observatory Based on fluorescence observations in coincidence with at least one Surface detector we derive a spectrum for energies above 10(18) eV We also update the previously published energy spectrum obtained with the surface detector array The two spectra are combined addressing the systematic uncertainties and, in particular. the influence of the energy resolution on the spectral shape The spectrum can be described by a broken power law E(-gamma) with index gamma = 3 3 below the ankle which is measured at log(10)(E(ankle)/eV) = 18 6 Above the ankle the spectrum is described by a power law with index 2 6 followed by a flux suppression, above about log(10)(E/eV) = 19 5, detected with high statistical significance (C) 2010 Elsevier B V All rights reserved

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 perforin calorimetric measurements of extensive air showers created by Cosmic rays of above 10(18) 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, ail area exceeding 3000 km(2). 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 oil air shower reconstructions. Between 10(18) and 10(20) 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. (C) 2010 Elsevier B.V. All rights reserved.

Estudio intertextual en dos cuentos de Borges : Pierre Menard, autor del Quijote y La biblioteca de Babel

This studyfocuses on the theory of intertextuality and on the most important approachesof Julia Kristeva, Gerard Genette and Ronald Barthestothis theory. It also examines the intertextual relationships in twoworksof Jorge Luis Borges:Pierre Menard, author of the Quixoteand The library of Babel. This studyconcludes that intertextual relations and issues are very often used in the works of Jorge Luis Borges. Analysis of histwoworks has shown the most obvious indicators of intertextuality such as allusions, quotations and references.

The sociology of Pierre Bourdieu and researching education policy

Bourdieu did not write anything explicitly about education policy. Despite this neglect, we agree with van Zanten that his theoretical concepts and methodological approaches can contribute to researching and understanding educational policy in the context of globalisation and the economising of it. In applying Bourdieu's theory and methodology to research in education policy, we focus on developing his work to understand what we call 'cross-field effects' and for exploring the emergence of a 'global education policy field'. These concepts are derived from some of our recent research concerning globalisation and mediatisation of education policy. The paper considers three separate issues. The first deals with Bourdieu' s primary 'thinking tools', namely practice, habitus,capitals and fields and their application to policy studies. The second and third sections consider two additions to Bourdieu's thinking tools, as a way to reconceptualise the functioning of policy if considered as a social field. More specifically, the second section develops an argument around cross-field effects, as a way to group together, research and describe policy effects. The third section develops an argument about an emergent global education policy field, and considers ways that such a field affects national education policy fields.

Pierre Hadot (1922-2010)

Pierre Hadot, classical philosopher and historian of philosophy, is best known for his conception of ancient philosophy as a bios or way of life (manière de vivre). His work has been widely influential in classical studies and on thinkers, including Michel Foucault. According to Hadot, twentieth- and twenty-first-century academic philosophy has largely lost sight of its ancient origin in a set of spiritual practices that range from forms of dialogue, via species of meditative reflection, to theoretical contemplation. These philosophical practices, as well as the philosophical discourses the different ancient schools developed in conjunction with them, aimed primarily to form, rather than only to inform, the philosophical student. The goal of the ancient philosophies, Hadot argued, was to cultivate a specific, constant attitude toward existence, by way of the rational comprehension of the nature of humanity and its place in the cosmos. This cultivation required, specifically, that students learn to combat their passions and the illusory evaluative beliefs instilled by their passions, habits, and upbringing. To cultivate philosophical discourse or writing without connection to such a transformed ethical comportment was, for the ancients, to be as a rhetorician or a sophist, not a philosopher. However, according to Hadot, with the advent of the Christian era and the eventual outlawing, in 529 C.E., of the ancient philosophical schools, philosophy conceived of as a bios largely disappeared from the West. Its spiritual practices were integrated into, and adapted by, forms of Christian monasticism. The philosophers’ dialectical techniques and metaphysical views were integrated into, and subordinated, first to revealed theology and then, later, to the modern natural sciences. However, Hadot maintained that the conception of philosophy as a bios has never completely disappeared from the West, resurfacing in Montaigne, Rousseau, Goethe, Thoreau, Nietzsche, and Schopenhauer, and even in the works of Descartes, Spinoza, Kant, and Heidegger.

Hadot’s conception of ancient philosophy and his historical narrative of its disappearance in the West have provoked both praise and criticism. Hadot received a host of letters from students around the world telling him that his works had changed their lives, perhaps the most fitting tribute given the nature of Hadot’s meta-philosophical claims. Unlike many of his European contemporaries, Hadot’s work is characterized by lucid, restrained prose; clarity of argument; the near-complete absence of recondite jargon; and a gentle, if sometimes self-depreciating, humor. While Hadot was an admirer of Nietzsche and Heidegger, and committed to a kind of philosophical recasting of the history of Western ideas, Hadot’s work lacks any eschatological sense of the end of philosophy, humanism, or the West. Late in life, Hadot would report that this was because he was animated by the sense that philosophy, as conceived and practiced in the ancient schools, remains possible for men and women of his era: “from 1970 on, I have felt very strongly that it was Epicureanism and Stoicism which could nourish the spiritual life of men and women of our times, as well as my own” (PWL 280).