Radiative Decay of a Long-Lived Particle and Big-Bang Nucleosynthesis

The effects of radiatively decaying, long-lived particles on big-bang nucleosynthesis (BBN) are discussed. If high-energy photons are emitted after BBN, they may change the abundances of the light elements through photodissociation processes, which may result in a significant discrepancy between the BBN theory and observation. We calculate the abundances of the light elements, including the effects of photodissociation induced by a radiatively decaying particle, but neglecting the hadronic branching ratio. Using these calculated abundances, we derive a constraint on such particles by comparing our theoretical results with observations. Taking into account the recent controversies regarding the observations of the light-element abundances, we derive constraints for various combinations of the measurements. We also discuss several models which predict such radiatively decaying particles, and we derive constraints on such models.Comment: Published version in Phys. Rev. D. Typos in figure captions correcte

Performance of the Pierre Auger Fluorescence Detector and Analysis of well recontructed events

The Pierre Auger Observatory is designed to elucidate the origin and nature of Ultra High Energy Cosmic Rays using a hybrid detection technique. A first run of data taking with a prototype version of both detectors (the so called Engineering Array) took place in 2001-2002, allowing the Collaboration to evaluate the performance of the two detector systems and to approach an analysis strategy. In this contribution, after a brief description of the system, we will report some results on the behavior of the Fluorescence Detector (FD) Prototype. Performance studies, such as measurements of noise, sensitivity and duty cycle, will be presented. We will illustrate a preliminary analysis of selected air showers. This analysis is performed using exclusively the information from the FD, and includes reconstruction of the shower geometry and of the longitudinal profil

A Study Of Very Inclined Showers In The Pierre Auger Observatory

The Engineering Array of the Auger Observatory has been running successfully since 2001 and inclined showers have been recorded from the start. We have analysed the events with zenith angle $>$ 70$^0$ recorded between May and November 2002. The different algorithms developed to analyze these showers are also discussed. An preliminary discussion of a reconstructed event having 20 detectors hit is presented. Inclined showers will be detected by the full Auger Observatory and they will allow significant enhancement of the array aperture. High energy events will be seen as spectacular events with 30 or 40 tanks triggered and they will provide alternative information on muon content in air showers

The Anisotropy Search Program For the Pierre Auger Observatory

The Pierre Auger Southern Observatory in Argentina has begun taking data as it is being developed up to a final enclosed area of 3000 square kilometres. A key aspect of the project is to provide information on the origin of the highest energy cosmic rays through understanding the arrival directions of those particles. To avoid claims of a spurious anisotropy detection because trials have not been properly accounted, the Auger Collaboration has agreed 'a priori' to the analysis prescription presented here. It specifies the following: 1. The accumulation time for the (future) data set to be analyzed. 2. The anisotropy 'targets', each assigned a chance probability level. 3. The analysis procedure for each trial. A positive result will be claimed for any target search only if its chance probability is less than its assigned level. The levels are chosen so that the total chance probability for one or more positive results is 0.001. Exploratory searches beyond this prescription will be encouraged, but the Auger Collaboration will not assign any confidence level to anisotropies that may be discovered that way. Any such discovery would identify a good target for a prescription to be used with a subsequent Auger data set

Calibration of the Pierre Auger fluorescence detector

The absolute calibration of an air fluorescence detector (FD) is an important element in correctly determining the energy of detected cosmic rays. The absolute calibration relates the flux of photons of a given wavelength at the detector aperture to the electronic signal recorded by the FD data acquisition system. For the Auger FDs, the primary absolute calibration method uses a diffusive surface which is placed in front of a telescope aperture to uniformly illuminate the telescope field of view with a known light signal. This single-wavelength measurement (375 nm) will be made at intervals of several months until the stability of the telescopes is determined. The relative wavelength dependence of the calibration is determined through independent measurements. The error in absolute calibration at a single wavelength is estimated to be less than 10%. Two other absolute calibration methods are used to provide an independent verification of the primary measurement. The stability of the calibration with time is monitored nightly by a relative calibration system. In this paper we will provide descriptions of the absolute and relative calibration methods used by the Auger air fluorescence observatory. Results from the calibration of the Auger Engineering Array telescopes will also be presented