The Pierre Auger Observatory

One of the foremost issues in astrophysics today is that of the origin of the ultra high energy cosmic rays. The Pierre Auger Observatory (PAO), currently under construction in the Province of Mendoza, Argentina, is a broadly based international effort to make a high statistic study of the upper-end of the cosmic ray spectrum. The PAO is the first experiment designed to work in a hybrid detection mode. It consists of an array of 1600 particle detectors spread over 3000 km2 and four fluorescence telescopes placed on the boundaries of the surface array. The concept of the experiment as well as the current status and future prospects are presented.Facultad de Ciencias Exacta

The Pierre Auger Observatory

One of the foremost issues in astrophysics today is that of the origin of the ultra high energy cosmic rays. The Pierre Auger Observatory (PAO), currently under construction in the Province of Mendoza, Argentina, is a broadly based international effort to make a high statistic study of the upper-end of the cosmic ray spectrum. The PAO is the first experiment designed to work in a hybrid detection mode. It consists of an array of 1600 particle detectors spread over 3000 km2 and four fluorescence telescopes placed on the boundaries of the surface array. The concept of the experiment as well as the current status and future prospects are presented.Facultad de Ciencias Exacta

Depth of maximum of air-shower profiles at the Pierre Auger Observatory : II. Composition implications

Using the data taken at the Pierre Auger Observatory between December 2004 and December 2012, we have examined the implications of the distributions of depths of atmospheric shower maximum (Xmax), using a hybrid technique, for composition and hadronic interaction models. We do this by fitting the distributions with predictions from a variety of hadronic interaction models for variations in the composition of the primary cosmic rays and examining the quality of the fit. Regardless of what interaction model is assumed, we find that our data are not well described by a mix of protons and iron nuclei over most of the energy range. Acceptable fits can be obtained when intermediate masses are included, and when this is done consistent results for the proton and iron-nuclei contributions can be found using the available models. We observe a strong energy dependence of the resulting proton fractions, and find no support from any of the models for a significant contribution from iron nuclei. However, we also observe a significant disagreement between the models with respect to the relative contributions of the intermediate components.La lista completa de autores que integran el documento puede consultarse en el archivo.Facultad de Ciencias Exacta

Depth of maximum of air-shower profiles at the Pierre Auger Observatory : II. Composition implications

Using the data taken at the Pierre Auger Observatory between December 2004 and December 2012, we have examined the implications of the distributions of depths of atmospheric shower maximum (Xmax), using a hybrid technique, for composition and hadronic interaction models. We do this by fitting the distributions with predictions from a variety of hadronic interaction models for variations in the composition of the primary cosmic rays and examining the quality of the fit. Regardless of what interaction model is assumed, we find that our data are not well described by a mix of protons and iron nuclei over most of the energy range. Acceptable fits can be obtained when intermediate masses are included, and when this is done consistent results for the proton and iron-nuclei contributions can be found using the available models. We observe a strong energy dependence of the resulting proton fractions, and find no support from any of the models for a significant contribution from iron nuclei. However, we also observe a significant disagreement between the models with respect to the relative contributions of the intermediate components.La lista completa de autores que integran el documento puede consultarse en el archivo.Facultad de Ciencias Exacta

The Pierre Auger Observatory

One of the foremost issues in astrophysics today is that of the origin of the ultra high energy cosmic rays. The Pierre Auger Observatory (PAO), currently under construction in the Province of Mendoza, Argentina, is a broadly based international effort to make a high statistic study of the upper-end of the cosmic ray spectrum. The PAO is the first experiment designed to work in a hybrid detection mode. It consists of an array of 1600 particle detectors spread over 3000 km2 and four fluorescence telescopes placed on the boundaries of the surface array. The concept of the experiment as well as the current status and future prospects are presented.Facultad de Ciencias Exacta

Spectral Calibration of the Fluorescence Telescopes of the Pierre Auger Observatory

We present a novel method to measure precisely the relative spectral response of the fluorescence telescopes of the Pierre Auger Observatory. We used a portable light source based on a xenon flasher and a monochromator to measure the relative spectral efficiencies of eight telescopes in steps of 5 nm from 280 nm to 440 nm. Each point in a scan had approximately 2 nm FWHM out of the monochromator. Different sets of telescopes in the observatory have different optical components, and the eight telescopes measured represent two each of the four combinations of components represented in the observatory. We made an end-to-end measurement of the response from different combinations of optical components, and the monochromator setup allowed for more precise and complete measurements than our previous multi-wavelength calibrations. We find an overall uncertainty in the calibration of the spectral response of most of the telescopes of 1.5% for all wavelengths; the six oldest telescopes have larger overall uncertainties of about 2.2%. We also report changes in physics measurables due to the change in calibration, which are generally small.Peer Reviewe

Probing heavy dark matter decays with multi-messenger astrophysical data

We set conservative constraints on decaying dark matter particles with masses spanning a very wide range ($10^4-10^{16}$ GeV). For this we use multimessenger observations of cosmic-ray (CR) protons/antiprotons, electrons/positrons, neutrinos/antineutrinos and gamma rays. Focusing on decays into the $\bar{b}b$ channel, we simulate the spectra of dark matter yields by using the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi equations and the $\texttt{Pythia}$ package. We then propagate the CRs of dark matter origin till Earth by using the state-of-the-art numerical frameworks $\texttt{CRPropa}$, $\texttt{GALPROP}$ and $\texttt{HelMod}$ for the solution of the CR transport equation in the extragalactic, Galactic region and the heliosphere, respectively. Conservative limits are obtained by requiring that the predicted dark matter spectra at Earth be less than the observed CR spectra. Overall, we exclude dark matter lifetimes of $10^{28}$ s or shorter for all the masses investigated in this work. The most stringent constraints reach $10^{30}$ s for very heavy dark matter particles with masses in the range $10^{11}-10^{14}$ GeV.Comment: 22 pages, 10 figures, V2: Minor changes to match JCAP published versio

Guaranteed- and high-precision evaluation of the Lambert W function

Solutions to a wide variety of transcendental equations can be expressed in terms of the Lambert W function. The W function, also occurring frequently in many branches of science, is a non-elementary but now standard mathematical function implemented in all major technical computing systems. In this work, we analyze an efficient logarithmic recursion with quadratic convergence rate to approximate its two real branches, W 0 and W -1 . We propose suitable starting values that ensure monotone convergence on the whole domain of definition of both branches. Then, we provide a priori, simple, explicit and uniform estimates on the convergence speed, which enable guaranteed, high-precision approximations of W 0 and W -1 at any point