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1.
Indications of anisotropy at large angular scales in the arrival directions of cosmic rays detected at the Pierre Auger Observatory
Marko Zavrtanik, Danilo Zavrtanik, Lili Yang, Serguei Vorobiov, Darko Veberič, Marta Trini, Samo Stanič, Ahmed Saleh, Gašper Kukec Mezek, Andrej Filipčič, Imen Al Samarai, 2015, published scientific conference contribution

Abstract: The large-scale distribution of arrival directions of high-energy cosmic rays carries major clues to understanding their origin. The Pierre Auger Collaboration have implemented different analyses to search for dipolar and quadrupolar anisotropies in different energy ranges spanning four orders of magnitude. A common phase ≈270◦ of the first harmonic modulation in right-ascension was found in adjacent energy intervals below 1 EeV, and another common phase ≈100◦ above 4 EeV. A constancy of phase measurements in ordered energy intervals originating from a genuine anisotropy is expected to appear with a smaller number of events than those needed to achieve significant amplitudes. This led us to design a prescribed test aimed at establishing whether this consistency in phases is real at 99% CL. The test required a total independent exposure of 21,000 km2 sr yr. We report on the status of this prescription. We also report the results of the search for a dipole anisotropy for cosmic rays with energies above 4 EeV using events with zenith angles between 60◦ and 80◦. Compared to previous analyses of events with zenith angles smaller than 60◦, this extension increases the size of the data set by 30%, and enlarges the fraction of exposed sky from 71% to 85%. The largest departure from isotropy is found in the energy range above 8 EeV, with an amplitude for the first harmonic in right ascension r1 = (4.4 ± 1.0) × 10[sup]−2, that has a chance probability P(≥ r1) = 6.4×10[sup]−5, reinforcing the hint previously reported with vertical events alone.
Found in: ključnih besedah
Summary of found: ...The large-scale distribution of arrival directions of high- energy cosmic rays carries major clues to understanding...
Keywords: high-energy cosmic rays large-scale distribution anisotropy studies Pierre Auger Observatory
Published: 02.03.2016; Views: 2991; Downloads: 186
.pdf Fulltext (862,90 KB)

2.
Large-Scale Distribution of Arrival Directions of Cosmic Rays Detected at the Pierre Auger Observatory and the Telescope Array above 10[sup]19 eV
Marko Zavrtanik, Danilo Zavrtanik, Lili Yang, Serguei Vorobiov, Darko Veberič, Marta Trini, Samo Stanič, Ahmed Saleh, Gašper Kukec Mezek, Andrej Filipčič, Olivier Deligny, 2015, published scientific conference contribution

Abstract: The large-scale distribution of arrival directions of high-energy cosmic rays is a key observable in attempts to understanding their origin. The dipole and quadrupole moments are of special interest in revealing potential anisotropies. An unambiguous measurement of these moments as well as of the full set of spherical harmonic coefficients requires full-sky coverage. This can be achieved by combining data from observatories located in both the northern and southern hemispheres. To this end, a joint analysis using data recorded at the Pierre Auger Observatory and the Telescope Array above 10[sup]19 eV has been performed. Thanks to the full-sky coverage, the measurement of the dipole moment reported in this study does not rely on any assumption on the underlying flux of cosmic rays. As well, the resolution on the quadrupole and higher order moments is the best ever obtained. The resulting multipolar expansion of the flux of cosmic rays allows a series of anisotropy searches to be performed, and in particular to report on the first angular power spectrum of cosmic rays. This allows a comprehensive description of the angular distribution of cosmic rays above 10[sup]19 eV.
Found in: ključnih besedah
Summary of found: ...The large-scale distribution of arrival directions of high- energy cosmic rays is a key observable in...
Keywords: Pierre Auger Observatory, Telescope Array, high-energy cosmic rays, large-scale anisotropies, angular power spectrum
Published: 08.03.2016; Views: 2642; Downloads: 138
.pdf Fulltext (462,61 KB)

3.
4.
Supergalactic Structure of Energy-Angle Correlations
P. Sokolsky, J. P. Lundquist, 2020, published scientific conference contribution

Abstract: Evidence for the supergalactic structure of multiplets (energy-angle correlations) has previously been shown using ultra-high energy cosmic ray (UHECR) data from Telescope Array (TA) with energies above 10^19 eV. The supergalactic deflection hypothesis (that UHECR sources and intervening magnetic fields are correlated) is measured by the all-sky behavior of the strength of intermediate-scale correlations. The multiplets are measured in spherical surface wedge bins of the field-of-view to account for uniform and random magnetic fields. The structure found is consistent with the previously published energy spectrum anisotropy results of TA and toy-model simulations of a supergalactic magnetic sheet. The 7 year data post-trial significance of this feature appearing by chance, on an isotropic sky, was found by Monte Carlo simulation to be ∼4σ. The analysis has now been applied to 10 years of data.
Found in: ključnih besedah
Summary of found: ...by the all-sky behavior of the strength of intermediate- scale correlations. The multiplets are measured in spherical...
Keywords: Cosmic rays, UHECR, energy spectrum, magnetic deflection, large-scale structure, supergalactic, multiplets
Published: 27.04.2020; Views: 975; Downloads: 40
.pdf Fulltext (1,66 MB)

5.
Supergalactic Structure of Multiplets with the Telescope Array Surface Detector
P. Sokolsky, J. P. Lundquist, 2019, published scientific conference contribution

Abstract: Evidence of supergalactic structure of multiplets has been found for ultra-high energy cosmic rays (UHECR) with energies above 10^19 eV using 7 years of data from the Telescope Array (TA) surface detector. The tested hypothesis is that UHECR sources, and intervening magnetic fields, may be correlated with the supergalactic plane, as it is a fit to the average matter density within the GZK horizon. This structure is measured by the average behavior of the strength of intermediate-scale correlations between event energy and position (multiplets). These multiplets are measured in wedge-like shapes on the spherical surface of the fieldof-view to account for uniform and random magnetic fields. The evident structure found is consistent with toy-model simulations of a supergalactic magnetic sheet and the previously published Hot/Coldspot results of TA. The post-trial probability of this feature appearing by chance, on an isotropic sky, is found by Monte Carlo simulation to be ~4.5σ.
Found in: ključnih besedah
Summary of found: ...of multiplets has been found for ultra-high energy cosmic rays (UHECR) with energies above 10^19... ...the average behavior of the strength of intermediate- scale correlations between event energy and position (multiplets)....
Keywords: UHECR, cosmic rays, energy spectrum, anisotropy, large-scale structure, magnetic deflection
Published: 28.04.2020; Views: 1072; Downloads: 68
.pdf Fulltext (1,38 MB)

6.
7.
Large-scale anisotropies above 0.03 EeV measured by the Pierre Auger Observatory
Lukas Zehrer, Marko Zavrtanik, Danilo Zavrtanik, Lili Yang, Serguei Vorobiov, Marta Trini, Samo Stanič, Gašper Kukec Mezek, Andrej Filipčič, Esteban Roulet, 2019, published scientific conference contribution

Found in: ključnih besedah
Summary of found: ...ultra-high energy cosmic rays (UHECRs), Pierre Auger Observatory, UHECR...
Keywords: ultra-high energy cosmic rays (UHECRs), Pierre Auger Observatory, UHECR arrival directions, large-scale anisotropies
Published: 24.07.2020; Views: 925; Downloads: 31
.pdf Fulltext (894,55 KB)

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