arXiv subjects

Pierre Auger Collaboration

Publications and source records attributed to Pierre Auger Collaboration.

24 records · Page 2Linked to original sources

arXiv2006

An upper limit to the photon fraction in cosmic rays above 10^19 eV from the Pierre Auger Observatory

An upper limit of 16% (at 95% c.l.) is derived for the photon fraction in cosmic rays with energies greater than 10^19 eV, based on observations of the depth of shower maximum performed with the hybrid detector of the Pierre Auger Observatory. This is the first such limit on photons obtained by observing the fluorescence light profile of air showers. This upper limit confirms and improves on previous results from the Haverah Park and AGASA surface arrays. Additional data recorded with the Auger surface detectors for a subset of the event sample, support the conclusion that a photon origin of the observed events is not favored.

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arXiv2006

Anisotropy studies around the galactic center

We present the first results for anisotropy searches around the galactic center at EeV energies using data from the Pierre Auger Observatory. Our analysis, based on a substantially larger data set, do not support previous claim of anisotropy found in this region by the AGASA and Sugar experiment. Furthermore we place un upper limit on a possible point like source located at the galactic center which exclude several scenarios predicting neutron sources in this location.

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arXiv2006

Extracting first science measurements from the southern detector of the Pierre Auger observatory

The world's largest cosmic-ray detector is nearing completion in the remote Pampas of Argentina. This instrument measures extensive air-showers with energies from ${10^{18}-10^{20}}$ eV and beyond. A surface detector array of area 3000 ${km^2}$ records the lateral distribution of charged particles at ground level. A fluorescence detector overlooking the surface detector records the longitudinal light profiles of showers in the atmosphere to make a calorimetric energy measurement. A ``test beam'' for the fluorescence detector is generated by a calibrated laser near the array center. This talk will focus on detector characterizations essential to the first science results that have been reported from the observatory. Plans to construct a larger instrument in the northern hemisphere will also be outlined.

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arXiv2005

Optical Relative Calibration and Stability Monitoring for the Auger Fluorescence Detector

The stability of the fluorescence telescopes of the Pierre Auger Observatory is monitored with the optical relative calibration setup. Optical fibers distribute light pulses to three different diffuser groups within the optical system. The total charge per pulse is measured for each pixel and compared with reference calibration measurements. This allows monitoring the short and long term stability with respect of the relative timing between pixels and the relative gain for each pixel. The designs of the LED calibration unit (LCU) and of the Xenon flash lamp used for relative calibration, are described and their capabilities to monitor the stability of the telescope performances are studied. We report the analysis of relative calibration data recorded during 2004. Fluctuations in the relative calibration constants provide a measure of the stability of the FD.

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arXiv2005

Quality studies of the data taking conditions for the Auger Fluorescence Detector

As more than half of the Fluorescence Detector (FD) of the Auger Observatory is completed, data taking is becoming a routine job. It is then necessary to follow strict procedures to assure the quality of the data. An overview of the data taking methods is given. The nature of the FD background signal is due to the night sky brightness (stars and planet faint light, moonlight, twilight, airglow, zodiacal and artificial light) and to the electronic background (photomultiplier and electronic noise). The analysis of the fluctuations in the FADC signal (variance analysis), directly proportional to the background mean light level, performed for each night of data taking is used to monitor the FD background signal. The data quality is analysed using different techniques, described in detail. Examples of trigger rates, number of stereo events, dead time due to moonlight, weather or hardware problems are given. The analysis comprises several months of data taking, giving an overview of the FD capabilities, performance and allowing a systematic study of data and their correlation with the environment.

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arXiv2005

Statistical and systematic uncertainties in the event reconstruction and S(1000) determination by the Pierre Auger surface detector

We discuss the statistical and systematic uncertainties in the event reconstruction (core location, and determination of S(1000), i.e., the signal at a distance of 1000 m from the shower core) by the Pierre Auger surface detector for showers with zenith angle less than 60 degrees. The method is based on a maximum likelihood method where the reference lateral distribution function is obtained through the experimental data. We also discuss S(1000) as primary energy estimator.

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