The Pierre Auger Observatory: Results on Ultra-High Energy Cosmic Rays

The focus of this article is on recent results on ultra-high energy cosmic rays obtained with the Pierre Auger Observatory. The world's largest instrument of this type and its performance are described. The observations presented here include the energy spectrum, the primary particle composition, limits on the fluxes of photons and neutrinos and a discussion of the anisotropic distribution of the arrival directions of the most energetic particles. Finally, plans for the construction of a Northern Auger Observatory in Colorado, USA, are discussed.Comment: Proceedings of the International Workshop on Advances in Cosmic Ray Science, Waseda University, Shinjuku, Tokyo, Japan, March 2008; to be published in the Journal of the Physical Society of Japan (JPSJ) supplemen

Description of Atmospheric Conditions at the Pierre Auger Observatory Using Meteorological Measurements and Models

Atmospheric conditions at the site of a cosmic ray observatory must be known well for reconstructing observed extensive air showers, especially when measured using the fluorescence technique. For the Pierre Auger Observatory, a sophisticated network of atmospheric monitoring devices has been conceived. Part of this monitoring was a weather balloon program to measure atmospheric state variables above the Observatory. To use the data in reconstructions of air showers, monthly models have been constructed. Scheduled balloon launches were abandoned and replaced with launches triggered by high-energetic air showers as part of a rapid monitoring system. Currently, the balloon launch program is halted and atmospheric data from numerical weather prediction models are used. A description of the balloon measurements, the monthly models as well as the data from the numerical weather prediction are presented

An Analytical Model for the Triaxial Collapse of Cosmological Perturbations

We present an analytical model for the non-spherical collapse of overdense regions out of a Gaussian random field of initial cosmological perturbations. The collapsing region is treated as an ellipsoid of constant density, acted upon by the quadrupole tidal shear from the surrounding matter. The dynamics of the ellipsoid is set by the ellipsoid self-gravity and the external quadrupole shear. Both forces are linear in the coordinates and therefore maintain homogeneity of the ellipsoid at all times. The amplitude of the external shear is evolved into the non-linear regime in thin spherical shells that are allowed to move only radially according to the mass interior to them. We describe how the initial conditions can be drawn in the appropriate correlated way from a random field of initial density perturbations. By considering many random realizations of the initial conditions, we calculate the distribution of shapes and angular momenta acquired by objects through the coupling of their quadrupole moment to the tidal shear. The average value of the spin parameter, 0.04, is found to be only weakly dependent on the system mass, the mean cosmological density, or the initial power spectrum of perturbations, in agreement with N-body simulations. For the cold dark matter power spectrum, most objects evolve from a quasi-spherical initial state to a pancake or filament and then to complete virialization. Low-spin objects tend to be more spherical. The evolution history of shapes is primarily induced by the external shear and not by the initial triaxiality of the objects. The statistical distribution of the triaxial shapes of collapsing regions can be used to test cosmological models against galaxy surveys on large scales.Comment: 42 pages, Tex, followed by 10 uuencoded figure

A Hierarchical Bayesian Model of Pitch Framing

Since the advent of high-resolution pitch tracking data (PITCHf/x), many in the sabermetrics community have attempted to quantify a Major League Baseball catcher's ability to "frame" a pitch (i.e. increase the chance that a pitch is called as a strike). Especially in the last three years, there has been an explosion of interest in the "art of pitch framing" in the popular press as well as signs that teams are considering framing when making roster decisions. We introduce a Bayesian hierarchical model to estimate each umpire's probability of calling a strike, adjusting for pitch participants, pitch location, and contextual information like the count. Using our model, we can estimate each catcher's effect on an umpire's chance of calling a strike.We are then able to translate these estimated effects into average runs saved across a season. We also introduce a new metric, analogous to Jensen, Shirley, and Wyner's Spatially Aggregate Fielding Evaluation metric, which provides a more honest assessment of the impact of framing