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The Pierre Auger Collaboration,
J. Abraham,
P Abreu,
M Aglietta,
C Aguirre,
E. J. Ahn,
D. Allard,
I. Allekotte,
J Allen,
J. Alvarez-Muñiz, [......],
T Yamamoto,
P. Younk,
G. Yuan,
A. Yushkov,
E. Zas,
D Zavrtanik,
M. Zavrtanik,
I Zaw,
A. Zepeda,
M Ziolkowski
[show abstract]
[hide abstract]
ABSTRACT: Studies of the cosmic ray energy spectrum at the highest energies with the Pierre Auger Observatory. Comment: Submissions to the 31st International Cosmic Ray Conference
06/2009;
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The Pierre Auger Collaboration,
J. Abraham,
P Abreu,
M Aglietta,
C Aguirre,
E. J. Ahn,
D. Allard,
I. Allekotte,
J Allen,
J. Alvarez-Muñiz, [......],
T Yamamoto,
P. Younk,
G. Yuan,
A. Yushkov,
E. Zas,
D Zavrtanik,
M. Zavrtanik,
I Zaw,
A. Zepeda,
M Ziolkowski
[show abstract]
[hide abstract]
ABSTRACT: Studies of the composition of the highest energy cosmic rays with the Pierre Auger Observatory, including examination of hadronic physics effects on the structure of extensive air showers. Submissions to the 31st ICRC, Lodz, Poland (July 2009). Comment: Submissions to the 31st International Cosmic Ray Conference, Lodz, Poland (July 2009)
06/2009;
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The Pierre Auger Collaboration: J. Abraham,
P. Abreu,
M. Aglietta,
C. Aguirre,
E. J. Ahn,
D. Allard,
I. Allekotte,
J. Allen,
J. Alvarez-Muñiz,
M. Ambrosio, [......],
T. Yamamoto,
P. Younk,
G. Yuan,
A. Yushkov,
E. Zas,
D. Zavrtanik,
M. Zavrtanik,
I. Zaw,
A. Zepeda,
M. Ziolkowski
[show abstract]
[hide abstract]
ABSTRACT: Studies of the correlations of ultra-high energy cosmic ray directions
with extra-Galactic objects, of general anisotropy, of photons and
neutrinos, and of other astrophysical effects, with the Pierre Auger
Observatory. Contributions to the 31st ICRC, Lodz, Poland, July 2009.
05/2009;
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The Pierre Auger Collaboration: J. Abraham,
P. Abreu,
M. Aglietta,
C. Aguirre,
E. J. Ahn,
D. Allard,
I. Allekotte,
J. Allen,
J. Alvarez-Muñiz,
M. Ambrosio, [......],
T. Yamamoto,
P. Younk,
G. Yuan,
A. Yushkov,
E. Zas,
D. Zavrtanik,
M. Zavrtanik,
I. Zaw,
A. Zepeda,
M. Ziolkowski
[show abstract]
[hide abstract]
ABSTRACT: Reports on the atmospheric monitoring, calibration, and other operating
systems of the Pierre Auger Observatory. Contributions to the 31st
International Cosmic Ray Conference, Lodz, Poland, July 2009.
05/2009;
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The Pierre Auger Collaboration: J. Abraham,
P. Abreu,
M. Aglietta,
C. Aguirre,
E. J. Ahn,
D. Allard,
I. Allekotte,
J. Allen,
J. Alvarez-Muñiz,
M. Ambrosio, [......],
T. Yamamoto,
P. Younk,
G. Yuan,
A. Yushkov,
E. Zas,
D. Zavrtanik,
M. Zavrtanik,
I. Zaw,
A. Zepeda,
M. Ziolkowski
[show abstract]
[hide abstract]
ABSTRACT: Technical reports on operations and features of the Pierre Auger
Observatory, including ongoing and planned enhancements and the status
of the future northern hemisphere portion of the Observatory.
Contributions to the 31st International Cosmic Ray Conference, Lodz,
Poland, July 2009.
05/2009;
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J Abraham,
P Abreu,
M Aglietta,
C Aguirre,
D Allard,
I Allekotte,
J Allen,
P Allison,
J Alvarez-Muñiz,
M Ambrosio, [......],
H Wu,
B Wundheiler,
T Yamamoto,
P Younk,
E Zas,
D Zavrtanik,
M Zavrtanik,
I Zaw,
A Zepeda,
M Ziolkowski
[show abstract]
[hide abstract]
ABSTRACT: The energy spectrum of cosmic rays above 2.5 x 10;{18} eV, derived from 20,000 events recorded at the Pierre Auger Observatory, is described. The spectral index gamma of the particle flux, J proportional, variantE;{-gamma}, at energies between 4 x 10;{18} eV and 4 x 10;{19} eV is 2.69+/-0.02(stat)+/-0.06(syst), steepening to 4.2+/-0.4(stat)+/-0.06(syst) at higher energies. The hypothesis of a single power law is rejected with a significance greater than 6 standard deviations. The data are consistent with the prediction by Greisen and by Zatsepin and Kuz'min.
Physical Review Letters 09/2008; 101(6):061101. · 7.37 Impact Factor
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J Abraham,
P Abreu,
M Aglietta,
C Aguirre,
D Allard,
I Allekotte,
J Allen,
P Allison,
J Alvarez-Muñiz,
M Ambrosio, [......],
H Wu,
B Wundheiler,
T Yamamoto,
P Younk,
E Zas,
D Zavrtanik,
M Zavrtanik,
A Zech,
A Zepeda,
M Ziolkowski
[show abstract]
[hide abstract]
ABSTRACT: 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.
Physical Review Letters 05/2008; 100(21):211101. · 7.37 Impact Factor
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J. Abraham,
P. Abreu,
M. Aglietta,
C. Aguirre,
D. Allard,
I. Allekotte,
J. Allen,
P. Allison,
J. Alvarez-Muñiz,
M. Ambrosio, [......],
H. Wu,
B. Wundheiler,
T. Yamamoto,
P. Younk,
E. Zas,
D. Zavrtanik,
M. Zavrtanik,
A. Zech,
A. Zepeda,
M. Ziolkowski
[show abstract]
[hide abstract]
ABSTRACT: A method is developed to search for air showers initiated by photons using data recorded by the surface detector of the Auger Observatory. The approach is based on observables sensitive to the longitudinal shower development, the signal risetime and the curvature of the shower front. Applying this method to the data, upper limits on the flux of photons of 3.8×10-3, above , are derived, with corresponding limits on the fraction of photons being 2.0%, 5.1%, and 31% (all limits at 95% c.l.). These photon limits disfavor certain exotic models of sources of cosmic rays. The results also show that the approach adopted by the Auger Observatory to calibrate the shower energy is not strongly biased by a contamination from photons.
Astroparticle Physics 05/2008; 29(4):243-256. · 3.22 Impact Factor
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J. Abraham,
P. Abreu,
M. Aglietta,
C. Aguirre,
D. Allard,
I. Allekotte,
J. Allen,
P. Allison,
J. Alvarez-Muñiz,
M. Ambrosio, [......],
H. Wu,
B. Wundheiler,
T. Yamamoto,
P. Younk,
E. Zas,
D. Zavrtanik,
M. Zavrtanik,
A. Zech,
A. Zepeda,
M. Ziolkowski
[show abstract]
[hide abstract]
ABSTRACT: Data collected by the Pierre Auger Observatory provide evidence for anisotropy in the arrival directions of the cosmic rays with the highest-energies, which are correlated with the positions of relatively nearby active galactic nuclei (AGN) [Pierre Auger Collaboration, Science 318 (2007) 938]. The correlation has maximum significance for cosmic rays with energy greater than ∼6 × 1019 eV and AGN at a distance less than ∼75 Mpc. We have confirmed the anisotropy at a confidence level of more than 99% through a test with parameters specified a priori, using an independent data set. The observed correlation is compatible with the hypothesis that cosmic rays with the highest-energies originate from extra-galactic sources close enough so that their flux is not significantly attenuated by interaction with the cosmic background radiation (the Greisen–Zatsepin–Kuz’min effect). The angular scale of the correlation observed is a few degrees, which suggests a predominantly light composition unless the magnetic fields are very weak outside the thin disk of our galaxy. Our present data do not identify AGN as the sources of cosmic rays unambiguously, and other candidate sources which are distributed as nearby AGN are not ruled out. We discuss the prospect of unequivocal identification of individual sources of the highest-energy cosmic rays within a few years of continued operation of the Pierre Auger Observatory.
Astroparticle Physics 04/2008; 29(3):188-204. · 3.22 Impact Factor
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J Abraham,
P Abreu,
M Aglietta,
C Aguirre,
D Allard,
I Allekotte,
J Allen,
P Allison,
C Alvarez,
J Alvarez-Muñiz, [......],
J Xu,
T Yamamoto,
P Younk,
E Zas,
D Zavrtanik,
M Zavrtanik,
A Zech,
A Zepeda,
M Ziolkowski,
B Kégl
[show abstract]
[hide abstract]
ABSTRACT: Using data collected at the Pierre Auger Observatory during the past 3.7 years, we demonstrated a correlation between the arrival directions of cosmic rays with energy above 6 x 10(19) electron volts and the positions of active galactic nuclei (AGN) lying within approximately 75 megaparsecs. We rejected the hypothesis of an isotropic distribution of these cosmic rays with at least a 99% confidence level from a prescribed a priori test. The correlation we observed is compatible with the hypothesis that the highest-energy particles originate from nearby extragalactic sources whose flux has not been substantially reduced by interaction with the cosmic background radiation. AGN or objects having a similar spatial distribution are possible sources.
Science 12/2007; 318(5852):938-43. · 31.20 Impact Factor
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J. Abraham,
M. Aglietta,
C. Aguirre,
D. Allard,
I. Allekotte,
P. Allison,
C. Alvarez,
J. Alvarez-Muñiz,
M. Ambrosio,
L. Anchordoqui, [......],
J. Xu,
T. Yamamoto,
P. Younk,
E. Zas,
D. Zavrtanik,
M. Zavrtanik,
A. Zech,
A. Zepeda,
M. Zha,
M. Ziolkowski
[show abstract]
[hide abstract]
ABSTRACT: Data from the Pierre Auger Observatory are analyzed to search for anisotropies near the direction of the Galactic Centre at EeV energies. The exposure of the surface array in this part of the sky is already significantly larger than that of the fore-runner experiments. Our results do not support previous findings of localized excesses in the AGASA and SUGAR data. We set an upper bound on a point-like flux of cosmic rays arriving from the Galactic Centre which excludes several scenarios predicting sources of EeV neutrons from Sagittarius A. Also the events detected simultaneously by the surface and fluorescence detectors (the ‘hybrid’ data set), which have better pointing accuracy but are less numerous than those of the surface array alone, do not show any significant localized excess from this direction.
Astroparticle Physics 03/2007; 27(4):244-253. · 3.22 Impact Factor
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J. Abraham,
M. Aglietta,
C. Aguirre,
D. Allard,
I. Allekotte,
P. Allison,
C. Alvarez,
J. Alvarez-Muñiz,
M. Ambrosio,
L. Anchordoqui, [......],
J. Xu,
T. Yamamoto,
P. Younk,
E. Zas,
D. Zavrtanik,
M. Zavrtanik,
A. Zech,
A. Zepeda,
M. Zha,
M. Ziolkowski
[show abstract]
[hide abstract]
ABSTRACT: An upper limit of 16% (at 95% c.l.) is derived for the photon fraction in cosmic rays with energies greater than 1019 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.
Astroparticle Physics 03/2007; 27(2-3):155-168. · 3.22 Impact Factor
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P. Abreu,
M. Aglietta,
M. Ahlers,
E. J. Ahn,
I. F. M. Albuquerque,
D. Allard,
I. Allekotte,
J. Allen,
P. Allison,
A. Almela, [......],
A. Yushkov,
B. Zamorano,
E. Zas,
D. Zavrtanik,
M. Zavrtanik,
I. Zaw,
A. Zepeda,
Y. Zhu,
M. Zimbres Silva,
M. Ziolkowski
[show abstract]
[hide abstract]
ABSTRACT: The Surface Detector of the Pierre Auger Observatory is sensitive to neutrinos of all flavors above 0.1 EeV. These interact through charged and neutral currents in the atmosphere giving rise to extensive air showers. When interacting deeply in the atmosphere at nearly horizontal incidence, neutrinos can be distinguished from regular hadronic cosmic rays by the broad time structure of their shower signals in the water-Cherenkov detectors. In this paper we present for the first time an analysis based on down-going neutrinos. We describe the search procedure, the possible sources of background, the method to compute the exposure and the associated systematic uncertainties. No candidate neutrinos have been found in data collected from 1 January 2004 to 31 May 2010. Assuming an E-2 differential energy spectrum the limit on the single-flavor neutrino is E2dN/dE<1.74×10-7GeVcm-2s-1sr-1 at 90% C.L. in the energy range 1×1017eV<E<1×1020eV.
Phys. Rev. D. 01/1970; 84(12).
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Pierre Auger The,
J Collaboration,
Abraham,
P Abreu,
M Aglietta,
C Aguirre,
E J Ahn,
D Allard,
I Allekotte,
J Allen, [......],
D Monnier Ragaigne,
F Montanet,
B Morales,
C Morello,
J C Moreno,
C Morris,
M Mostafá,
C A Moura,
S Mueller,
M A Muller
J. Coppens Hojvat K.H. Kampert T. Karova R.M. Kieckhafer J. Kleinfeller R. Knapik J. Knapp J.L. Navarro P. Necesal C. Newman-Holmes P.T. Nhung J. Oehlschläger V.M. Olmos-Gilbaja J. Pallotta. 01/1927; 27(27).
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J. Abraham,
P. Abreu,
M. Aglietta,
C. Aguirre,
E.J. Ahn,
D. Allard,
I. Allekotte,
J. Allen,
P. Allison,
J. Alvarez-Muñiz, [......],
H. Wu,
B. Wundheiler,
P. Younk,
G. Yuan,
E. Zas,
D. Zavrtanik,
M. Zavrtanik,
I. Zaw,
A. Zepeda,
M. Ziolkowski
[show abstract]
[hide abstract]
ABSTRACT: From direct observations of the longitudinal development of ultra-high energy air showers performed with the Pierre Auger Observatory, upper limits of 3.8%, 2.4%, 3.5% and 11.7% (at 95% c.l.) are obtained on the fraction of cosmic-ray photons above 2, 3, 5 and 10 EeV , respectively. These are the first experimental limits on ultra-high energy photons at energies below 10 EeV. The results complement previous constraints on top–down models from array data and they reduce systematic uncertainties in the interpretation of shower data in terms of primary flux, nuclear composition and proton-air cross-section.
Astroparticle Physics.
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J. Abraham,
P. Abreu,
M. Aglietta,
C. Aguirre,
E.J. Ahn,
D. Allard,
I. Allekotte,
J. Allen,
P. Allison,
J. Alvarez-Muñiz, [......],
B. Wundheiler,
T. Yamamoto,
P. Younk,
G. Yuan,
E. Zas,
D. Zavrtanik,
M. Zavrtanik,
I. Zaw,
A. Zepeda,
M. Ziolkowski
[show abstract]
[hide abstract]
ABSTRACT: Atmospheric parameters, such as pressure (P), temperature (T) and density (ρ∝P/T), affect the development of extensive air showers initiated by energetic cosmic rays. We have studied the impact of atmospheric variations on extensive air showers by means of the surface detector of the Pierre Auger Observatory. The rate of events shows a ∼10% seasonal modulation and ∼2% diurnal one. We find that the observed behaviour is explained by a model including the effects associated with the variations of P and ρ. The former affects the longitudinal development of air showers while the latter influences the Molière radius and hence the lateral distribution of the shower particles. The model is validated with full simulations of extensive air showers using atmospheric profiles measured at the site of the Pierre Auger Observatory.
Astroparticle Physics.
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J. Abraham,
P. Abreu,
M. Aglietta,
E.J. Ahn,
D. Allard,
J. Allen,
J. Alvarez-Muñiz,
M. Ambrosio,
L. Anchordoqui,
S. Andringa, [......],
T. Yamamoto,
P. Younk,
G. Yuan,
A. Yushkov,
E. Zas,
D. Zavrtanik,
M. Zavrtanik,
I. Zaw,
A. Zepeda,
M. Ziolkowski
[show abstract]
[hide abstract]
ABSTRACT: We report a measurement of the flux of cosmic rays with unprecedented precision and statistics using the Pierre Auger Observatory. Based on fluorescence observations in coincidence with at least one surface detector we derive a spectrum for energies above 1018 eV. We also update the previously published energy spectrum obtained with the surface detector array. The two spectra are combined addressing the systematic uncertainties and, in particular, the influence of the energy resolution on the spectral shape. The spectrum can be described by a broken power law E−γ with index γ=3.3 below the ankle which is measured at log10(Eankle/eV)=18.6. Above the ankle the spectrum is described by a power law with index 2.6 followed by a flux suppression, above about log10(E/eV)=19.5, detected with high statistical significance.
Physics Letters B.
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J. Abraham,
P. Abreu,
M. Aglietta,
C. Aguirre,
E.J. Ahn,
D. Allard,
I. Allekotte,
J. Allen,
J. Alvarez-Muñiz,
M. Ambrosio, [......],
T. Yamamoto,
P. Younk,
G. Yuan,
A. Yushkov,
E. Zas,
D. Zavrtanik,
M. Zavrtanik,
I. Zaw,
A. Zepeda,
M. Ziolkowski
[show abstract]
[hide abstract]
ABSTRACT: The air fluorescence detector of the Pierre Auger Observatory is designed to perform calorimetric measurements of extensive air showers created by cosmic rays of above . To correct these measurements for the effects introduced by atmospheric fluctuations, the Observatory contains a group of monitoring instruments to record atmospheric conditions across the detector site, an area exceeding 3000 km2. The atmospheric data are used extensively in the reconstruction of air showers, and are particularly important for the correct determination of shower energies and the depths of shower maxima. This paper contains a summary of the molecular and aerosol conditions measured at the Pierre Auger Observatory since the start of regular operations in 2004, and includes a discussion of the impact of these measurements on air shower reconstructions. Between 1018 and , the systematic uncertainties due to all atmospheric effects increase from 4% to 8% in measurements of shower energy, and to in measurements of the shower maximum.
Astroparticle Physics. 33(2):108-129.
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D. Allard,
E. Armengaud,
J. Aublin,
T. Beau,
C. Berat,
P Billoir,
O. Blanch-Bigas,
C. Bonifazi,
M Boratav,
N.G. Busca, [......],
C. Wileman,
M. G. Winnick,
B. Wundheiler,
T Yamamoto,
P. Younk,
E. Zas,
D Zavrtanik,
M. Zavrtanik,
A. Zepeda,
M Ziolkowski
[show abstract]
[hide abstract]
ABSTRACT: The surface detector array of the Pierre Auger Observatory is sensitive to Earth-skimming tau-neutrinos $\nu_\tau$ that interact in the 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 is 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 $E_\nu^{2}~\mathrm{d}N_{\nu_\tau}/\mathrm{d}E_{\nu} < 1.3 \times 10^{-7}$ GeV cm$^{-2}$ s$^{-1}$ sr$^{-1}$ in the energy range $2\times10^{17} \mathrm{eV} < E_\nu < 2\times10^{19}$~eV.
Physical Review Letters.
