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11.
The Cosmic Ray Energy Spectrum between 2 PeV and 2 EeV Observed with the TALE Detector in Monocular Mode
J. P. Lundquist, R.U. Abbasi, 2018, izvirni znanstveni članek

Opis: We report on a measurement of the cosmic ray energy spectrum by the Telescope Array Low-Energy Extension (TALE) air fluorescence detector (FD). The TALE air FD is also sensitive to the Cherenkov light produced by shower particles. Low-energy cosmic rays, in the PeV energy range, are detectable by TALE as Cherenkov events. Using these events, we measure the energy spectrum from a low energy of ~2 PeV to an energy greater than 100 PeV. Above 100 PeV, TALE can detect cosmic rays using air fluorescence. This allows for the extension of the measurement to energies greater than a few EeV. In this paper, we describe the detector, explain the technique, and present results from a measurement of the spectrum using ~1000 hr of observation. The observed spectrum shows a clear steepening near 10^17.1 eV, along with an ankle-like structure at 10^16.2 eV. These features present important constraints on the origin of galactic cosmic rays and on propagation models. The feature at 10^17.1 eV may also mark the end of the galactic cosmic ray flux and the start of the transition to extragalactic sources.
Najdeno v: ključnih besedah
Povzetek najdenega: ...light produced by shower particles. Low-energy cosmic rays, in the PeV energy range, are detectable... ...astroparticle physics, cosmic rays, UHECR, energy spectrum...
Ključne besede: astroparticle physics, cosmic rays, UHECR, energy spectrum
Objavljeno: 30.04.2020; Ogledov: 440; Prenosov: 0
.pdf Polno besedilo (4,40 MB)

12.
Study of muons from ultrahigh energy cosmic ray air showers measured with the Telescope Array experiment
J. P. Lundquist, R.U. Abbasi, 2018, izvirni znanstveni članek

Opis: One of the uncertainties in the interpretation of ultrahigh energy cosmic ray data comes from the hadronic interaction models used for air shower Monte Carlo (MC) simulations. The number of muons observed at the ground from ultrahigh energy cosmic ray–induced air showers is expected to depend upon the hadronic interaction model. One may therefore test the hadronic interaction models by comparing the measured number of muons with the MC prediction. In this paper, we present the results of studies of muon densities in ultrahigh energy extensive air showers obtained by analyzing the signal of surface detector stations which should have high muon purity. The muon purity of a station will depend on both the inclination of the shower and the relative position of the station. In seven years’ data from the Telescope Array experiment, we find that the number of particles observed for signals with an expected muon purity of ∼65% at a lateral distance of 2000 m from the shower core is 1.72± 0.10(stat)±0.37(syst) times larger than the MC prediction value using the QGSJET II-03 model for proton-induced showers. A similar effect is also seen in comparisons with other hadronic models such as QGSJET II-04, which shows a 1.67±0.10±0.36 excess. We also studied the dependence of these excesses on lateral distances and found a slower decrease of the lateral distribution of muons in the data as compared to the MC, causing larger discrepancy at larger lateral distances.
Najdeno v: ključnih besedah
Povzetek najdenega: ...UHECR, cosmic rays, muons, particle physics...
Ključne besede: UHECR, cosmic rays, muons, particle physics
Objavljeno: 30.04.2020; Ogledov: 421; Prenosov: 0
.pdf Polno besedilo (2,16 MB)

13.
Search for correlations between the arrival directions of IceCube neutrino events and ultrahigh-energy cosmic rays detected by the Pierre Auger Observatory and the Telescope Array
J. P. Lundquist, M. G. Aartsen, 2016, izvirni znanstveni članek

Opis: This paper presents the results of different searches for correlations between very high-energy neutrino candidates detected by IceCube and the highest-energy cosmic rays measured by the Pierre Auger Observatory and the Telescope Array. We first consider samples of cascade neutrino events and of high-energy neutrino-induced muon tracks, which provided evidence for a neutrino flux of astrophysical origin, and study their cross-correlation with the ultrahigh-energy cosmic ray (UHECR) samples as a function of angular separation. We also study their possible directional correlations using a likelihood method stacking the neutrino arrival directions and adopting different assumptions on the size of the UHECR magnetic deflections. Finally, we perform another likelihood analysis stacking the UHECR directions and using a sample of through-going muon tracks optimized for neutrino point-source searches with sub-degree angular resolution. No indications of correlations at discovery level are obtained for any of the searches performed. The smallest of the p-values comes from the search for correlation between UHECRs with IceCube high-energy cascades, a result that should continue to be monitored.
Najdeno v: ključnih besedah
Povzetek najdenega: ...UHECR, cosmic rays, neutrinos, multi-messenger physics, anisotropy...
Ključne besede: UHECR, cosmic rays, neutrinos, multi-messenger physics, anisotropy
Objavljeno: 30.04.2020; Ogledov: 441; Prenosov: 0
.pdf Polno besedilo (2,49 MB)

14.
Correlations of the arrival directions of ultra-high energy cosmic ray with extragalactic objects as observed by the telescope array experiment
J. P. Lundquist, T. Abu-Zayyad, 2013, izvirni znanstveni članek

Opis: We search for correlations between the positions of extragalactic objects and the arrival directions of ultra-high energy cosmic rays (UHECRs) with primary energy E ≥ 40 EeV as observed by the surface detector array of the Telescope Array (TA) experiment during the first 40 months of operation. We examine several public astronomical object catalogs, including the Veron-Cetty and Veron catalog of active galactic nuclei. We count the number of TA events correlated with objects in each catalog as a function of three parameters: the maximum angular separation between a TA event and an object, the minimum energy of the events, and the maximum redshift of the objects. We determine the combination of these parameters that maximizes the correlations, and we calculate the probability of having the same levels of correlations from an isotropic distribution of UHECR arrival directions. No statistically significant correlations are found when penalties for scanning over the above parameters and for searching in several catalogs are taken into account.
Najdeno v: ključnih besedah
Povzetek najdenega: ...the arrival directions of ultra-high energy cosmic rays (UHECRs) with primary energy E ≥ 40... ...acceleration of particles, astroparticle physics, cosmic rays...
Ključne besede: acceleration of particles, astroparticle physics, cosmic rays
Objavljeno: 19.05.2020; Ogledov: 406; Prenosov: 25
.pdf Polno besedilo (779,07 KB)

15.
Search for anisotropy of ultrahigh energy cosmic rays with the Telescope Array experiment
J. P. Lundquist, T. Abu-Zayyad, 2012, izvirni znanstveni članek

Opis: We study the anisotropy of Ultra-High Energy Cosmic Ray (UHECR) events collected by the Telescope Array (TA) detector in the first 40 months of operation. Following earlier studies, we examine event sets with energy thresholds of 10 EeV, 40 EeV, and 57 EeV. We find that the distributions of the events in right ascension and declination are compatible with an isotropic distribution in all three sets. We then compare with previously reported clustering of the UHECR events at small angular scales. No significant clustering is found in the TA data. We then check the events with E > 57 EeV for correlations with nearby active galactic nuclei. No significant correlation is found. Finally, we examine all three sets for correlations with the large-scale structure (LSS) of the universe. We find that the two higher-energy sets are compatible with both an isotropic distribution and the hypothesis that UHECR sources follow the matter distribution of the universe (the LSS hypothesis), while the event set with E > 10 EeV is compatible with isotropy and is not compatible with the LSS hypothesis at 95% CL unless large deflection angles are also assumed. We show that accounting for UHECR deflections in a realistic model of the Galactic magnetic field can make this set compatible with the LSS hypothesis.
Najdeno v: ključnih besedah
Povzetek najdenega: ...acceleration of particles, astroparticle physics, cosmic rays, magnetic fields, methods: statistical, relativistic...
Ključne besede: acceleration of particles, astroparticle physics, cosmic rays, magnetic fields, methods: statistical, relativistic processes
Objavljeno: 19.05.2020; Ogledov: 399; Prenosov: 0
.pdf Polno besedilo (1,04 MB)

16.
Evidence for a Supergalactic Structure of Magnetic Deflection Multiplets of Ultra-High Energy Cosmic Rays
J. P. Lundquist, R. Abbasi, 2020, izvirni znanstveni članek

Opis: Evidence for a large-scale supergalactic cosmic ray multiplet (arrival directions correlated with energy) structure is reported for ultra-high energy cosmic ray (UHECR) energies above 10^19 eV using seven years of data from the Telescope Array (TA) surface detector and updated to 10 years. Previous energy-position correlation studies have made assumptions regarding magnetic field shapes and strength, and UHECR composition. Here the assumption tested is that, since the supergalactic plane is a fit to the average matter density of the local Large Scale Structure (LSS), UHECR sources and intervening extragalactic magnetic fields are correlated with this plane. This supergalactic deflection hypothesis is tested by the entire field-of-view (FOV) behavior of the strength of intermediate-scale energy-angle correlations. These multiplets are measured in spherical cap section bins (wedges) of the FOV to account for coherent and random magnetic fields. The structure found is consistent with supergalactic deflection, the previously published energy spectrum anisotropy results of TA (the hotspot and coldspot), and toy-model simulations of a supergalactic magnetic sheet. The seven year data post-trial significance of this supergalactic structure of multiplets appearing by chance, on an isotropic sky, is found by Monte Carlo simulation to be 4.19σ. The ten years of data post-trial significance is 4.09σ. Furthermore, the starburst galaxy M82 is shown to be a possible source of the TA Hotspot, and an estimate of the supergalactic magnetic field using UHECR measurements is presented.
Najdeno v: ključnih besedah
Povzetek najdenega: ...astroparticle physics, cosmic rays, UHECR, supergalactic plane, multiplets, magnetic...
Ključne besede: astroparticle physics, cosmic rays, UHECR, supergalactic plane, multiplets, magnetic deflection, large-scale structure of universe
Objavljeno: 19.05.2020; Ogledov: 338; Prenosov: 0
.pdf Polno besedilo (4,40 MB)

17.
Constraining dark matter particle properties with Fermi-LAT and the Cherenkov Telescope Array
Christopher Eckner, 2020, doktorska disertacija

Najdeno v: ključnih besedah
Povzetek najdenega: ...dark matter, astroparticle physics, high-energy gamma-ray astronomy, cosmic rays, Imaging Atmospheric Cherenkov Telescope, Cherenkov Telescope...
Ključne besede: dark matter, astroparticle physics, high-energy gamma-ray astronomy, cosmic rays, Imaging Atmospheric Cherenkov Telescope, Cherenkov Telescope Array, Fermi Large Area Telescope
Objavljeno: 29.09.2020; Ogledov: 304; Prenosov: 13
.pdf Polno besedilo (68,77 MB)

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