The analog signal processing board for the HEAT telescopes

Abstract The aim of the Pierre Auger Observatory is to measure with high statistics the flux, the arrival directions and the mass composition of cosmic rays at the highest energies. Since 2009, the Auger Collaboration has added three new High Elevation Auger Telescopes (HEAT) along with a new 25 km 2 infill array in the field of view of the new telescopes. These enhancements have lowered the energy threshold of the Observatory by about an order of magnitude. In combination with the existing telescopes in Coihueco the vertical field of view is extended to about 60°, allowing the measurement of nearby air showers arising from primaries with energies as low as 2×10 17 eV. In this paper we describe the new front-end analog board developed to process the signals generated by the photomultipliers of the HEAT telescopes. Eighty analog boards have been produced, fully characterized and tested. The main characteristics of the electronic circuits and the circuit parameters are illustrated

The arcade project

The Atmospheric Research for Climate and Astroparticle Detection (ARCADE) project aims to a better comprehension of the limits of applicability, systematics and possible enhancements of the typical techniques used for the measurement of the aerosol attenuation profiles of UV light in cosmic rays and gamma rays experiments. Aerosols are indeed the most variable component in the atmosphere on a short time scale, and experiments based on the detection of the UV light in atmosphere need a continuous monitoring of the aerosol stratification to obtain a reliable evaluation of the properties of the primary particles. The ARCADE project is measuring the aerosol attenuation of UV light due to aerosols with multiple techniques and instruments simultaneously on the same air mass. For this purpose, a Raman + elastic Lidar with a laser source at 355 nm has been built and is currently taking data in Lamar, Colorado together with the Atmospheric Monitoring Telescope (AMT) to detect UV light at a distance of 40 km from the Lidar laser source. The system has been installed on site in 2014 and data were taken every month during moonless nights for one year. A full simulation of the AMT system has been developed. The setup and simulation of the system, together with the AMT calibration system and first collected data are shown

Highlights from the Pierre Auger Observatory

The Pierre Auger Observatory is the world's largest cosmic ray observatory. Our current exposure reaches nearly 40,000 km$^2$ str and provides us with an unprecedented quality data set. The performance and stability of the detectors and their enhancements are described. Data analyses have led to a number of major breakthroughs. Among these we discuss the energy spectrum and the searches for large-scale anisotropies. We present analyses of our X$_{max}$ data and show how it can be interpreted in terms of mass composition. We also describe some new analyses that extract mass sensitive parameters from the 100% duty cycle SD data. A coherent interpretation of all these recent results opens new directions. The consequences regarding the cosmic ray composition and the properties of UHECR sources are briefly discussed.Comment: 9 pages, 12 figures, talk given at the 33rd International Cosmic Ray Conference, Rio de Janeiro 201

A search for point sources of EeV photons

Measurements of air showers made using the hybrid technique developed with the fluorescence and surface detectors of the Pierre Auger Observatory allow a sensitive search for point sources of EeV photons anywhere in the exposed sky. A multivariate analysis reduces the background of hadronic cosmic rays. The search is sensitive to a declination band from -85{\deg} to +20{\deg}, in an energy range from 10^17.3 eV to 10^18.5 eV. No photon point source has been detected. An upper limit on the photon flux has been derived for every direction. The mean value of the energy flux limit that results from this, assuming a photon spectral index of -2, is 0.06 eV cm^-2 s^-1, and no celestial direction exceeds 0.25 eV cm^-2 s^-1. These upper limits constrain scenarios in which EeV cosmic ray protons are emitted by non-transient sources in the Galaxy.Comment: 28 pages, 10 figures, accepted for publication in The Astrophysical Journa

Reconstruction of inclined air showers detected with the Pierre Auger Observatory

We describe the method devised to reconstruct inclined cosmic-ray air showers with zenith angles greater than $60^\circ$ detected with the surface array of the Pierre Auger Observatory. The measured signals at the ground level are fitted to muon density distributions predicted with atmospheric cascade models to obtain the relative shower size as an overall normalization parameter. The method is evaluated using simulated showers to test its performance. The energy of the cosmic rays is calibrated using a sub-sample of events reconstructed with both the fluorescence and surface array techniques. The reconstruction method described here provides the basis of complementary analyses including an independent measurement of the energy spectrum of ultra-high energy cosmic rays using very inclined events collected by the Pierre Auger Observatory.Comment: 27 pages, 19 figures, accepted for publication in Journal of Cosmology and Astroparticle Physics (JCAP

The Pierre Auger Observatory: Contributions to the 34th International Cosmic Ray Conference (ICRC 2015)

Contributions of the Pierre Auger Collaboration to the 34th International Cosmic Ray Conference, 30 July - 6 August 2015, The Hague, The NetherlandsComment: 24 proceedings, the 34th International Cosmic Ray Conference, 30 July - 6 August 2015, The Hague, The Netherlands; will appear in PoS(ICRC2015

Measurement of the cosmic ray spectrum above 4×10184{\times}10^{18} eV using inclined events detected with the Pierre Auger Observatory

A measurement of the cosmic-ray spectrum for energies exceeding $4{\times}10^{18}$ eV is presented, which is based on the analysis of showers with zenith angles greater than $60^{\circ}$ detected with the Pierre Auger Observatory between 1 January 2004 and 31 December 2013. The measured spectrum confirms a flux suppression at the highest energies. Above $5.3{\times}10^{18}$ eV, the "ankle", the flux can be described by a power law $E^{-\gamma}$ with index $\gamma=2.70 \pm 0.02 \,\text{(stat)} \pm 0.1\,\text{(sys)}$ followed by a smooth suppression region. For the energy ($E_\text{s}$) at which the spectral flux has fallen to one-half of its extrapolated value in the absence of suppression, we find $E_\text{s}=(5.12\pm0.25\,\text{(stat)}^{+1.0}_{-1.2}\,\text{(sys)}){\times}10^{19}$ eV.Comment: Replaced with published version. Added journal reference and DO