An upper limit to the photon fraction in cosmic rays above 1019eV from the Pierre Auger Observatory

Abstract

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.

Ultrahigh-energy cosmic-ray bounds on nonbirefringent modified Maxwell theory

“…The Pierre Auger Collaboration has published a table of 29 UHECR events with energies above 10 EeV ≡ 10 19 eV [16]. In addition, the atmospheric depth of the shower maximum, X max , was determined for all of these events.…”

“…We have also accounted for the increased missing-energy correction in case of a nuclear primary, that is, the energies given in Ref. [16] (which refer to photon primaries) were increased by 7 %, according to Ref. [39].…”

“…[16] for the definition of ∆ γ ]; (3) primary energy between 10 and 30 EeV. The first (and most selective) criterion aims at rejecting heavier nuclei.…”

“…[13,14]). In this article, we obtain even better bounds for all nine nonbirefringent parameters from selected UHECR events recorded by the Pierre Auger Observatory [15] over the period January 2004 to February 2006 [16].…”

Measurement of the aerosol phase function at the Pierre Auger Observatory

“…While still under construction, scientific data taking began in 2004, and first results have been published [1,2,3].…”