Browsing by Autor "Jeff Allen"

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A study of the effect of molecular and aerosol conditions in the atmosphere on air fluorescence measurements at the Pierre Auger Observatory
(Elsevier BV, 2010) J. Abraham; P. Abreu; M. Aglietta; C. Aguirre; E. J. Ahn; D. Allard; I. Allekotte; Jeff Allen; Jaime Álvarez-Muñiz; M. Ambrosio
Correlation of the highest-energy cosmic rays with the positions of nearby active galactic nuclei
(Elsevier BV, 2008) J. Abraham; P. Abreu; M. Aglietta; C. Aguirre; D. Allard; I. Allekotte; Jeff Allen; P. Allison; Jaime Álvarez-Muñiz; M. Ambrosio
Limit on the diffuse flux of ultrahigh energy tau neutrinos with the surface detector of the Pierre Auger Observatory
(American Physical Society, 2009) J. Abraham; P. Abreu; M. Aglietta; C. Aguirre; E. J. Ahn; D. Allard; I. Allekotte; Jeff Allen; P. Allison; Jaime Álvarez-Muñiz
Data collected at the Pierre Auger Observatory are used to establish an upper limit on the diffuse flux of tau neutrinos in the cosmic radiation. Earth-skimming ${\ensuremath{\nu}}_{\ensuremath{\tau}}$ may interact in the Earth's crust and produce a $\ensuremath{\tau}$ lepton by means of charged-current interactions. The $\ensuremath{\tau}$ lepton may emerge from the Earth and decay in the atmosphere to produce a nearly horizontal shower with a typical signature, a persistent electromagnetic component even at very large atmospheric depths. The search procedure to select events induced by $\ensuremath{\tau}$ decays against the background of normal showers induced by cosmic rays is described. The method used to compute the exposure for a detector continuously growing with time is detailed. Systematic uncertainties in the exposure from the detector, the analysis, and the involved physics are discussed. No $\ensuremath{\tau}$ neutrino candidates have been found. For neutrinos in the energy range $2\ifmmode\times\else\texttimes\fi{}{10}^{17}\text{ }\text{ }\mathrm{eV}<{E}_{\ensuremath{\nu}}<2\ifmmode\times\else\texttimes\fi{}{10}^{19}\text{ }\text{ }\mathrm{eV}$, assuming a diffuse spectrum of the form ${E}_{\ensuremath{\nu}}^{\ensuremath{-}2}$, data collected between 1 January 2004 and 30 April 2008 yield a 90% confidence-level upper limit of ${E}_{\ensuremath{\nu}}^{2}d{N}_{{\ensuremath{\nu}}_{\ensuremath{\tau}}}/d{E}_{\ensuremath{\nu}}<9\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}\text{ }\text{ }\mathrm{GeV}\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}2}\text{ }{\mathrm{s}}^{\ensuremath{-}1}\text{ }\text{ }{\mathrm{sr}}^{\ensuremath{-}1}$.
The fluorescence detector of the Pierre Auger Observatory
(Elsevier BV, 2010) J. Abraham; P. Abreu; M. Aglietta; C. Aguirre; E. J. Ahn; D. Allard; I. Allekotte; Jeff Allen; P. Allison; Jaime Álvarez-Muñiz
Upper Limit on the Diffuse Flux of Ultrahigh Energy Tau Neutrinos from the Pierre Auger Observatory
(American Physical Society, 2008) J. Abraham; P. Abreu; M. Aglietta; C. Aguirre; D. Allard; I. Allekotte; Jeff Allen; P. Allison; Jaime Álvarez-Muñiz; M. Ambrosio
The surface detector array of the Pierre Auger Observatory is sensitive to Earth-skimming tau neutrinos that interact in Earth's crust. Tau leptons from nu(tau) charged-current interactions can emerge and decay in the atmosphere to produce a nearly horizontal shower with a significant electromagnetic component. The data collected between 1 January 2004 and 31 August 2007 are used to place an upper limit on the diffuse flux of nu(tau) at EeV energies. Assuming an E(nu)(-2) differential energy spectrum the limit set at 90% C.L. is E(nu)(2)dN(nu)(tau)/dE(nu)<1.3 x 10(-7) GeV cm(-2) s(-1) sr(-1) in the energy range 2 x 10(17) eV< E(nu)< 2 x 10(19) eV.