21. Performance of the Cherenkov Telescope ArrayMarko Zavrtanik, Danilo Zavrtanik, Gabrijela Zaharijas, Lili Yang, Serguei Vorobiov, Samo Stanič, Gašper Kukec Mezek, Christopher Eckner, G. Maier, 2017, published scientific conference contribution Found in: ključnih besedah
Summary of found: ...CTA,
Monte Carlo simulations,
gamma rays...
Keywords: CTA, Monte Carlo simulations, gamma rays
Published: 16.02.2018; Views: 1228; Downloads: 85
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28. Search for point sources of ultra-high-energy photons with the Telescope Array surface detectorJ. P. Lundquist, R.U. Abbasi, 2020, original scientific article Abstract: The surface detector (SD) of the Telescope Array (TA) experiment allows us to detect indirectly photons with energies of the order of 10^18 eV and higher, and to separate photons from the cosmic ray background. In this paper, we present the results of a blind search for point sources of ultra-high-energy (UHE) photons in the Northern sky using the TA SD data. The photon-induced extensive air showers are separated from the hadron-induced extensive air shower background by means of a multivariate classifier based upon 16 parameters that characterize the air shower events. No significant evidence for the photon point sources is found. The upper limits are set on the flux of photons from each particular direction in the sky within the TA field of view, according to the experiment’s angular resolution for photons. The average 95 per cent confidence level upper-limits for the point-source flux of photons with energies greater than 10^18, 10^18.5, 10^19, 10^19.5 and 10^20 eV are 0.094, 0.029, 0.010, 0.0073 and 0.0058 km−2yr−1, respectively. For energies higher than 10^18.5 eV, the photon point-source limits are set for the first time. Numerical results for each given direction in each energy range are provided as a supplement to this paper.
Found in: ključnih besedah
Summary of found: ...methods: data analysis, cosmic rays, gamma-rays: general...
Keywords: methods: data analysis, cosmic rays, gamma-rays: general
Published: 29.04.2020; Views: 652; Downloads: 0
Fulltext (1,05 MB) |
29. Gamma Ray Showers Observed at Ground Level in Coincidence With Downward Lightning LeadersJ. P. Lundquist, R.U. Abbasi, 2018, original scientific article Abstract: Bursts of gamma ray showers have been observed in coincidence with downward propagating negative leaders in lightning flashes by the Telescope Array Surface Detector (TASD). The TASD is a 700‐km^2 cosmic ray observatory located in southwestern Utah, USA. In data collected between 2014 and 2016, correlated observations showing the structure and temporal development of three shower‐producing flashes were obtained with a 3‐D lightning mapping array, and electric field change measurements were obtained for an additional seven flashes, in both cases colocated with the TASD. National Lightning Detection Network information was also used throughout. The showers arrived in a sequence of 2–5 short‐duration (≤10 μs) bursts over time intervals of several hundred microseconds and originated at an altitude of ≃3–5 km above ground level during the first 1–2 ms of downward negative leader breakdown at the beginning of cloud‐to‐ground lightning flashes. The shower footprints, associated waveforms and the effect of atmospheric propagation indicate that the showers consist primarily of downward‐beamed gamma radiation. This has been supported by GEANT simulation studies, which indicate primary source fluxes of ≃10^12–10^14 photons for 16° half‐angle beams. We conclude that the showers are terrestrial gamma ray flashes, similar to those observed by satellites, but that the ground‐based observations are more representative of the temporal source activity and are also more sensitive than satellite observations, which detect only the most powerful terrestrial gamma ray flashes.
Found in: ključnih besedah
Summary of found: ...gamma rays, lightning, gamma ray bursts, surface detector...
Keywords: gamma rays, lightning, gamma ray bursts, surface detector
Published: 30.04.2020; Views: 786; Downloads: 0
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