Correlation of the highest-energy cosmic rays with the positions of nearby active galactic nuclei

Data collected by the Pierre Auger Observatory provide evidence for anisotropy in the arrival directions of the cosmic rays with the highest-energies, which are correlated with the positions of relatively nearby active galactic nuclei (AGN) [Pierre Auger Collaboration, Science 318 (2007) 938]. The correlation has maximum significance for cosmic rays with energy greater than similar to 6 x 10(19) eV and AGN at a distance less than similar to 75 Mpc. We have confirmed the anisotropy at a confidence level of more than 99% through a test with parameters specified a priori, using an independent data set. The observed correlation is compatible with the hypothesis that cosmic rays with the highest-energies originate from extra-galactic sources close enough so that their flux is not significantly attenuated by interaction with the cosmic background radiation (the Greisen-Zatsepin-Kuz`min effect). The angular scale of the correlation observed is a few degrees, which suggests a predominantly light composition unless the magnetic fields are very weak outside the thin disk of our galaxy. Our present data do not identify AGN as the sources of cosmic rays unambiguously, and other candidate sources which are distributed as nearby AGN are not ruled out. We discuss the prospect of unequivocal identification of individual sources of the highest-energy cosmic rays within a few years of continued operation of the Pierre Auger Observatory. (C) 2008 Elsevier B.V. All rights reserved.

Advanced functionality for radio analysis in the Offline software framework of the Pierre Auger Observatory

The advent of the Auger Engineering Radio Array (AERA) necessitates the development of a powerful framework for the analysis of radio measurements of cosmic ray air showers. As AERA performs ""radio-hybrid"" measurements of air shower radio emission in coincidence with the surface particle detectors and fluorescence telescopes of the Pierre Auger Observatory, the radio analysis functionality had to be incorporated in the existing hybrid analysis solutions for fluorescence and surface detector data. This goal has been achieved in a natural way by extending the existing Auger Offline software framework with radio functionality. In this article, we lay out the design, highlights and features of the radio extension implemented in the Auger Offline framework. Its functionality has achieved a high degree of sophistication and offers advanced features such as vectorial reconstruction of the electric field, advanced signal processing algorithms, a transparent and efficient handling of FFTs, a very detailed simulation of detector effects, and the read-in of multiple data formats including data from various radio simulation codes. The source code of this radio functionality can be made available to interested parties on request. (C) 2011 Elsevier B.V. All rights reserved.

Photoproduction of J/psi and of high mass e(+)e(-) in ultra-peripheral Au plus Au collisions at root s(NN)=200 GeV

We present the first measurement of photoproduction of J/psi and of two-photon production of high-mass e(+)e(-) pairs in electromagnetic (or ultra-peripheral) nucleus-nucleus interactions, using Au + Au data at root s(NN) = 200 GeV. The events are tagged with forward neutrons emitted following Coulomb excitation of one or both Au* nuclei. The event sample consists of 28 events with m(e+e-) > 2 GeV/c(2) with zero like-sign background. The measured cross sections at midrapidity of d sigma/dy (J/psi + Xn, y = 0) = 76 +/- 33 (stat) +/- 11 (syst) pb and d(2)sigma /dm dy (e(+) e(-) + Xn, y = 0) = 86 +/- 23(stat) +/- 16(syst) mu b/ (GeV/c(2)) for m(e+e-) epsilon vertical bar 2.0, 2.8 vertical bar GeV/c(2) have been compared and found to be consistent with models for photoproduction of J/psi and QED based calculations of two-photon production of e(+)e(-) pairs. (C) 2009 Elsevier B.V. All rights reserved.

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.

Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter

Data collected by the Pierre Auger Observatory through 31 August 2007 showed evidence for anisotropy in the arrival directions of cosmic rays above the Greisen-Zatsepin-Kuz`min energy threshold, 6 x 10(19) eV. The anisotropy was measured by the fraction of arrival directions that are less than 3.1 degrees from the position of an active galactic nucleus within 75 Mpc (using the Veron-Cetty and Veron 12th catalog). An updated measurement of this fraction is reported here using the arrival directions of cosmic rays recorded above the same energy threshold through 31 December 2009. The number of arrival directions has increased from 27 to 69, allowing a more precise measurement. The correlating fraction is (38(-6)(+7))%, compared with 21% expected for isotropic cosmic rays. This is down from the early estimate of (69-(+11)(13))%. The enlarged set of arrival directions is examined also in relation to other populations of nearby extragalactic objects: galaxies in the 2 Microns All Sky Survey and active galactic nuclei detected in hard X-rays by the Swift Burst Alert Telescope. A celestial region around the position of the radiogalaxy Cen A has the largest excess of arrival directions relative to isotropic expectations. The 2-point autocorrelation function is shown for the enlarged set of arrival directions and compared to the isotropic expectation. (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.

Análise de necessidades de inglês para fins específicos em um curso de graduação em turismo

This study presents the results of a survey conducted in the area of English for Specific Purposes (ESP) in order to identify (1) the learning needs of students in a course in Tourism, their desires and lacks, at a federal university, with respect to use of English; (2) the needs of the present situation of teachers and the coordinator of that course as to the language; (3) the needs of the target situation of professionals (graduates) and companies with respect to this language. This research is a case study (STAKE, 1998; YIN, 2009) and was used for data collection, instruments such as questionnaires, semi-structured interviews, and document on the Tourism Course. To this end, it was adopted the theoretical basis for the constructs of English for Specific Purposes (ESP) Inglês para Fins Específicos (IFE) in Brazil, also known as Inglês Instrumental, whose foundation is based on the work by Hutchinson and Waters (1987), Robinson (1991), Dudley-Evans and St. John (1998), Celani, Deyes, Holmes, Scott (2006), among others, since this work is devoted to a specific area, Tourism. Results show that students opined the ability to prioritize reading and speaking into the classroom. Professionals reported that the latter is an indispensable tool for entering the labor market, yet they feel unprepared and need to attend English language courses in private language schools. The testimony of company executives also point to this deficiency. Finally, the present situation of teachers reveals that, while advocating the use of English in the classroom, this is not because students prefer their mother tongue. There is also an evident lack of needs analysis. Eventually, the coordinator said that there is some uncertainty as to the methodology, content and language skills worked, and the lack of interaction among teachers of English. It was concluded, therefore, it is important to conduct a needs analysis so that one can redesign a course that meets the different contextual needs: students, teachers, coordination, represented by the institutional needs, and the labor market