Search

The hybrid design of the Pierre Auger Observatory allows for the measurement of the properties of extensive air showers initiated by ultra-high energy cosmic rays with unprecedented precision. By using an array of prototype underground muon detectors, we have performed the first direct measurement, by the Auger Collaboration, of the muon content of air showers between 2 × 10¹⁷ and 2 × 10¹⁸ eV. We have studied the energy evolution of the attenuation-corrected muon density, and compared it to predictions from air shower simulations. The observed densities are found to be larger than those predicted by models. We quantify this discrepancy by combining the measurements from the muon detector with those from the Auger fluorescence detector at 1017.5 eV and 10¹⁸ eV. We find that, for the models to explain the data, an increase in the muon density of 38% ± 4%(12%) ± 21%18% for EPOS- LHC, and of 50%(53%) ± 4%(13%) ± 23%20% for QGSJetII- 04, is respectively needed., La lista completa de autores que integran el documento puede consultarse en el archivo., Facultad de Ciencias Exactas, Instituto de Física La Plata

We search for signals of magnetically-induced effects in the arrival directions of ultra-high-energy cosmic rays detected at the Pierre Auger Observatory. We apply two different methods. One is a search for sets of events that show a correlation between their arrival direction and the inverse of their energy, which would be expected if they come from the same point-like source, they have the same electric charge and their deflection is relatively small and coherent. We refer to these sets of events as "multiplets". The second method, called "thrust", is a principal axis analysis aimed to detect the elongated patterns in a region of interest. We study the sensitivity of both methods using a benchmark simulation and we apply them to data in two different searches. The first search is done assuming as source candidates a list of nearby active galactic nuclei and starburst galaxies. The second is an all-sky blind search. We report the results and we find no statistically significant features. We discuss the compatibility of these results with the indications on the mass composition inferred from data of the Pierre Auger Observatory., La lista completa de autores puede verse en el archivo asociado., Instituto de Física La Plata

En este trabajo se estudian las Redes Generativas Antagónicas (GANs) y sus aplicaciones a través de una extensa revisión de bibliografía teórica y de los últimos artículos científicos publicados sobre el tema. Se describen los modelos estadísticos generativos en contraposición con los discriminativos y se estudian las partes que componen las GANs, su entrena- miento y dificultades. Este trabajo contempla, además, la implementación de una Red Generativa Antagónica de Super-Resolución (SRGAN) mediante las librerías Keras y Tensorflow. Se utiliza para su entrenamiento el entorno Google Colaboratory, que permite la utilización de una GPU. En esta implementación se obtienen imágenes cualitativamente de alta calidad, que se pueden apreciar tanto utilizando como entrada imágenes del conjunto de prueba, como imágenes sin relación al conjunto de datos utilizado para entrenar la red., In this project, Adversarial Generative Neural Networks (GANs) and their applications are studied through an extensive review of theoretical literature and the latest scientific papers published. Generative statistical models are described in opposition to discriminatory models. The different blocks that componse a GAN are studied, as well as their training and the difficulties it involves. This project also contemplates the implementation of a Super-Resolution Adversarial Generative Network (SRGAN) presented in [1], using the libraries Keras and Tensorflow. The Google Colaboratory environment is used for training the GAN, since the platform allows the use of a GPU NVIDIA Tesla K80. In this implementation, qualitatively high quality images are obtained, which can be appreciated both using as inputimages of the test set and images unrelated to the data set used to train the network., Facultad de Informática

Neutrinos with energies above 10¹⁷ eV are detectable with the Surface Detector Array of the Pierre Auger Observatory. The identification is efficiently performed for neutrinos of all flavors interacting in the atmosphere at large zenith angles, as well as for Earth-skimming tau neutrinos with nearly tangential trajectories relative to the Earth. No neutrino candidates were found in similar to 14.7 years of data taken up to 31 August 2018. This leads to restrictive upper bounds on their flux. The 90% C.L. single-flavor limit to the diffuse flux of ultra-high-energy neutrinos with an E-nu(⁻²) spectrum in the energy range 1.0 x 10¹⁷ eV-2.5 x 10¹⁹ eV is E(²)dN(nu)/dE(nu), Instituto de Física La Plata

The determination of the primary energy of extensive air showers using the uorescence detection technique requires an estimation of the energy carried away by particles that do not deposit all their energy in the atmosphere. This estimation is typically made using Monte Carlo simulations and thus depends on the assumed primary particle mass and on model predictions for neutrino and muon production. In this work we present a new method to obtain the invisible energy from events detected by the Pierre Auger Observatory. The method uses measurements of the muon number at ground level, and it allows us to reduce signi cantly the systematic uncertainties related to the mass composition and the high energy hadronic interaction models, and consequently to improve the estimation of the energy scale of the Observatory., La nómina completa de autores puede verse en el archivo asociado al ítem., Facultad de Ciencias Exactas

With the Surface Detector array (SD) of the Pierre Auger Observatory we can detect neutrinos with energy between 10(¹⁷) eV and 10(²⁰) eV from point-like sources across the sky, from close to the Southern Celestial Pole up to 60° in declination, with peak sensitivities at declinations around ∼ 53° and ∼ +55°, and an unmatched sensitivity for arrival directions in the Northern hemisphere. A search has been performed for highly-inclined air showers induced by neutrinos of all flavours with no candidate events found in data taken between 1 Jan 2004 and 31 Aug 2018. Upper limits on the neutrino flux from point-like steady sources have been derived as a function of source declination. An unrivaled sensitivity is achieved in searches for transient sources with emission lasting over an hour or less, if they occur within the field of view corresponding to the zenith angle range between 60° and 95° where the SD of the Pierre Auger Observatory is most sensitive to neutrinos., Instituto de Física La Plata

The profile of the longitudinal development of showers produced by ultra-high energy cosmic rays carries information related to the interaction properties of the primary particles with atmospheric nuclei. In this work, we present the first measurement of the average shower profile in traversed atmospheric depth at the Pierre Auger Observatory. The shapes of profiles are well reproduced by the Gaisser-Hillas parametrization within the range studied, for E > 1017:8 eV. A detailed analysis of the systematic uncertainties is performed using 10 years of data and a full detector simulation. The average shape is quantified using two variables related to the width and asymmetry of the profile, and the results are compared with predictions of hadronic interaction models for different primary particles., La lista completa de autores puede verse en el archivo asociado., Instituto de Física La Plata

With the Auger Engineering Radio Array (AERA) of the Pierre Auger Observatory, we have observed the radio emission from 561 extensive air showers with zenith angles between 60 and 84 . In contrast to air showers with more vertical incidence, these inclined air showers illuminate large ground areas of several km2 with radio signals detectable in the 30 to 80MHz band. A comparison of the measured radio-signal amplitudes with Monte Carlo simulations of a subset of 50 events for which we reconstruct the energy using the Auger surface detector shows agreement within the uncertainties of the current analysis. As expected for forward-beamed radio emission undergoing no significant absorption or scattering in the atmosphere, the area illuminated by radio signals grows with the zenith angle of the air shower. Inclined air showers with EeV energies are thus measurable with sparse radio-antenna arrays with grid sizes of a km or more. This is particularly attractive as radio detection provides direct access to the energy in the electromagnetic cascade of an air shower, which in case of inclined air showers is not accessible by arrays of particle detectors on the ground., La lista completa de autores puede verse en el archivo asociado., Instituto de Física La Plata