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112. Constraints on the diffuse photon flux with energies above 10^18 eV using the surface detector of the Telescope Array experimentR.U. Abbasi, Jon Paul Lundquist, 2018, original scientific article Abstract: We present the results of the search for ultra-high-energy photons with nine years of data from the Telescope Array surface detector. A multivariate classifier is built upon 16 reconstructed parameters of the extensive air shower. These parameters are related to the curvature and the width of the shower front, the steepness of the lateral distribution function, and the timing parameters of the waveforms sensitive to the shower muon content. A total number of two photon candidates found in the search is fully compatible with the expected background. The 95% CL limits on the diffuse flux of the photons with energies greater than 10^18.0, 10^18.5, 10^19.0, 10^19.5 and 10^20.0 eV are set at the level of 0.067, 0.012, 0.0036, 0.0013, correspondingly.
Keywords: Ultra-high-energy photons, Telescope array experiment, Extensive air showers
Published in RUNG: 30.04.2020; Views: 2950; Downloads: 0
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113. TA Anisotropy SummaryK. Kawata, Jon Paul Lundquist, 2019, published scientific conference contribution Abstract: The Telescope Array (TA) is the largest ultra-high-energy cosmic-ray (UHECR) detector in the northern hemisphere. It consists of an array of 507 surface detectors (SD) covering a total 700 km^2 and three fluorescence detector stations overlooking the SD array. In this proceedings, we summarize recent results on the search for directional anisotropy of UHECRs using the latest dataset collected by the TA SD array. We obtained hints of the anisotropy of the UHECRs in the northern sky from the various analyses.
Keywords: cosmic radiation, UHE detector, fluorescence detector, surface, Telescope Array Experiment, anisotropy, experimental results
Published in RUNG: 28.04.2020; Views: 2950; Downloads: 78
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114. Covering the celestial sphere at ultra-high energies: Full-sky cosmic-ray maps beyond the ankle and the flux suppressionJ. Biteau, Jon Paul Lundquist, 2019, published scientific conference contribution Abstract: Despite deflections by Galactic and extragalactic magnetic fields, the distribution of ultra-high energy cosmic rays (UHECRs) over the celestial sphere remains a most promising observable for the identification of their sources. Thanks to a large number of detected events over the past years, a large-scale anisotropy at energies above 8 EeV has been identified, and there are also indications from the Telescope Array and Pierre Auger Collaborations of deviations from isotropy at intermediate angular scales (about 20 degrees) at the highest energies. In this contribution, we map the flux of UHECRs over the full sky at energies beyond each of two major features in the UHECR spectrum – the ankle and the flux suppression, and we derive limits for anisotropy on different angular scales in the two energy regimes. In particular, full-sky coverage enables constraints on low-order multipole moments without assumptions about the strength of higher-order multipoles. Following previous efforts from the two Collaborations, we build full-sky maps accounting for the relative exposure of the arrays and differences in the energy normalizations. The procedure relies on cross-calibrating the UHECR fluxes reconstructed in the declination band around the celestial equator covered by both observatories. We present full-sky maps at energies above ~10 EeV and ~50 EeV, using the largest datasets shared across UHECR collaborations to date. We report on anisotropy searches exploiting full-sky coverage and discuss possible constraints on the distribution of UHECR sources.
Keywords: UHECR, cosmic rays, anisotropy, Telescope Array, Pierre Auger Observatory
Published in RUNG: 28.04.2020; Views: 2587; Downloads: 82
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115. Indications of Proton-Dominated Cosmic-Ray Composition above 1.6 EeVR.U. Abbasi, Jon Paul Lundquist, 2010, original scientific article Abstract: We report studies of ultrahigh-energy cosmic-ray composition via analysis of depth of air shower maximum (Xmax), for air shower events collected by the High-Resolution Fly’s Eye (HiRes) observatory. The HiRes data are consistent with a constant elongation rate d⟨Xmax⟩/d[log(E)] of 47.9 ± 6.0 (stat) ± 3.2 (syst) g/cm^2/decade for energies between 1.6 and 63 EeV, and are consistent with a predominantly protonic composition of cosmic rays when interpreted via the QGSJET01 and QGSJET-II high-energy hadronic interaction models. These measurements constrain models in which the galactic-to-extragalactic transition is the cause of the energy spectrum ankle at 4×10^18 eV.
Keywords: Cosmic rays, Energy spectrum, Telescope Array, Hybrid, Ultra high energy
Published in RUNG: 27.04.2020; Views: 2733; Downloads: 0
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116. The hybrid energy spectrum of Telescope Array’s Middle Drum Detector and surface arrayR.U. Abbasi, Jon Paul Lundquist, 2015, original scientific article Abstract: The Telescope Array experiment studies ultra high energy cosmic rays using a hybrid detector. Fluorescence telescopes measure the longitudinal development of the extensive air shower generated when a primary cosmic ray particle interacts with the atmosphere. Meanwhile, scintillator detectors measure the lateral distribution of secondary shower particles that hit the ground. The Middle Drum (MD) fluorescence telescope station consists of 14 telescopes from the High Resolution Fly’s Eye (HiRes) experiment, providing a direct link back to the HiRes measurements. Using the scintillator detector data in conjunction with the telescope data improves the geometrical reconstruction of the showers significantly, and hence, provides a more accurate reconstruction of the energy of the primary particle. The Middle Drum hybrid spectrum is presented and compared to that measured by the Middle Drum station in monocular mode. Further, the hybrid data establishes a link between the Middle Drum data and the surface array. A comparison between the Middle Drum hybrid energy spectrum and scintillator Surface Detector (SD) spectrum is also shown.
Keywords: Cosmic rays, Energy spectrum, Telescope Array, Hybrid, Ultra high energy
Published in RUNG: 27.04.2020; Views: 2688; Downloads: 0
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117. Study of Ultra-High Energy Cosmic Ray composition using Telescope Array’s Middle Drum detector and surface array in hybrid modeR.U. Abbasi, Jon Paul Lundquist, 2015, original scientific article Abstract: Previous measurements of the composition of Ultra-High Energy Cosmic Rays (UHECRs) made by the High Resolution Fly’s Eye (HiRes) and Pierre Auger Observatory (PAO) are seemingly contradictory, but utilize different detection methods, as HiRes was a stereo detector and PAO is a hybrid detector. The five year Telescope Array (TA) Middle Drum hybrid composition measurement is similar in some, but not all, respects in methodology to PAO, and good agreement is evident between data and a light, largely protonic, composition when comparing the measurements to predictions obtained with the QGSJetII-03 and QGSJet-01c models. These models are also in agreement with previous HiRes stereo measurements, confirming the equivalence of the stereo and hybrid methods. The data is incompatible with a pure iron composition, for all models examined, over the available range of energies. The elongation rate and mean values of are in good agreement with Pierre Auger Observatory data. This analysis is presented using two methods: data cuts using simple geometrical variables and a new pattern recognition technique.
Keywords: Ultra-High Energy Cosmic Rays, Cosmic ray composition, Atmospheric fluorescence, Extensive air shower array, Hybrid, Telescope Array
Published in RUNG: 24.04.2020; Views: 2989; Downloads: 0
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118. Raman LIDARs and atmospheric calibration along the line-of-sight of the Cherenkov Telescope ArraySamo Stanič, Longlong Wang, Marko Zavrtanik, 2019, published scientific conference contribution Abstract: The Cherenkov Telescope Array (CTA) is the next generation ground-based observatory for
gamma-ray astronomy at very-high energies. Employing more than 100 (north and south sites)
Imaging Atmospheric Cherenkov Telescopes in the northern and southern hemispheres, it was
designed to reach unprecedented sensitivity and energy resolution. Understanding and correcting
for systematic biases on the absolute energy scale and instrument response functions will be a cru-
cial issue for the performance of CTA. The Montpellier group and the Spanish/Italian/Slovenian
collaboration are currently building two Raman LIDAR prototypes for the online atmospheric cal-
ibration along the line-of-sight of the CTA. Requirements for such a solution include the ability
to characterize aerosol extinction at two wavelengths to distances up to 30 km with an accuracy
better than 5%, within exposure time scales of about a minute, steering capabilities and close
interaction with the CTA array control and data acquisition system as well as other auxiliary in-
struments. Our Raman LIDARs have design features that make them different from those used
in atmospheric science and are characterized by large collecting mirrors (∼2.5 m 2 ), liquid light-
guides that collect the light at the focal plane and transport it to the readout system, reduced
acquisition time and highly precise Raman spectrometers. The Raman LIDARs will participate in
a cross-calibration and characterization campaign of the atmosphere at the CTA North site at La
Palma, together with other site characterization instruments. After a one-year test period there, an
in-depth evaluation of the solutions adopted by the two projects will lead to a final Raman LIDAR
design proposal for both CTA sites.
Keywords: Raman lidar atmospheric calibration Cherenkov Telescope Array
Published in RUNG: 29.08.2019; Views: 3434; Downloads: 102
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119. Monte Carlo studies for the optimisation of the Cherenkov Telescope Array layoutA. Acharyya, Samo Stanič, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, 2019, original scientific article Keywords: very-high energy gamma-ray astronomy, Cherenkov Telescope Array, array layout optimisation, Monte Carlo studies
Published in RUNG: 18.04.2019; Views: 3085; Downloads: 0
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120. Testing the agreement between the Xmax distributions measured by the Pierre Auger and Telescope Array ObservatoriesV. De Souza, Andrej Filipčič, Gašper Kukec Mezek, Ahmed Saleh, Samo Stanič, Marta Trini, Darko Veberič, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, 2017, published scientific conference contribution Keywords: Xmax distributions, Pierre Auger Observatory, Telescope Array
Published in RUNG: 19.02.2018; Views: 3775; Downloads: 179
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