41. 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: 2975; Downloads: 0
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42. Evidence of Intermediate-scale Energy Spectrum Anisotropy of Cosmic Rays E ≥ 10^19.2 eV with the Telescope Array Surface DetectorR.U. Abbasi, Jon Paul Lundquist, 2018, original scientific article Abstract: Evidence for an intermediate-scale energy spectrum anisotropy has been found in the arrival directions of ultra-high energy cosmic rays for energies greater than 10^19.2 eV in the northern hemisphere using 7 years of Telescope Array surface detector data. A relative energy distribution test is done comparing events inside oversampled spherical caps of equal exposure, to those outside, using the Poisson likelihood ratio. The center of maximum significance is at 9h16m, 45°, and has a deficit of events with energies 10^19.2 ≤ E < 10^19.75 eV and an excess for E ≥ 10^19.75 eV. The post-trial probability of this energy anisotropy, appearing by chance anywhere on an isotropic sky, is found by Monte Carlo simulation to be 9 × 10−5 (3.74σ global).
Keywords: astroparticle physics, cosmic rays, anisotropy, large-scale structure of universe
Published in RUNG: 24.04.2020; Views: 2972; Downloads: 196
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43. A Northern Sky Survey for Point-Like Sources of EeV Neutral Particles with the Telescope Array ExperimentR.U. Abbasi, Jon Paul Lundquist, 2015, original scientific article Abstract: We report on the search for steady point-like sources of neutral particles around 1018 eV between 2008 and 2013
May with the scintillator SD of the Telescope Array experiment. We found overall no significant point-like excess
above 0.5 EeV in the northern sky. Subsequently, we also searched for coincidence with the Fermi bright Galactic
sources. No significant coincidence was found within the statistical uncertainty. Hence, we set an upper limit on the
neutron flux that corresponds to an averaged flux of 0.07 km−2 yr−1 for E > 1EeV in the northern sky at the 95%
confidence level. This is the most stringent flux upper limit in a northern sky survey assuming point-like sources.
The upper limit at the 95% confidence level on the neutron flux from Cygnus X-3 is also set to 0.2 km−2 yr−1 for
E > 0.5 EeV. This is an order of magnitude lower than previous flux measurements.
Keywords: acceleration of particles, cosmic rays, surveys
Published in RUNG: 24.04.2020; Views: 3568; Downloads: 0
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44. Indications of Intermediate-Scale Anisotropy of Cosmic Rays with Energy Greater Than 57 EeV in the Northern Sky Measured with the Surface Detector of the Telescope Array ExperimentR.U. Abbasi, Jon Paul Lundquist, 2014, original scientific article Abstract: We have searched for intermediate-scale anisotropy in the arrival directions of ultrahigh-energy cosmic rays with energies above 57 EeV in the northern sky using data collected over a 5 year period by the surface detector of the Telescope Array experiment. We report on a cluster of events that we call the hotspot, found by oversampling using 20∘-radius circles. The hotspot has a Li-Ma statistical significance of 5.1σ, and is centered at R.A.=146.7∘, Dec.=43.2∘. The position of the hotspot is about 19∘ off of the supergalactic plane. The probability of a cluster of events of 5.1σ significance, appearing by chance in an isotropic cosmic-ray sky, is estimated to be 3.7×10−4 (3.4σ).
Keywords: acceleration of particles, cosmic rays, large-scale structure of universe, surveys
Published in RUNG: 24.04.2020; Views: 3022; Downloads: 0
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45. Report of the Working Group on the Composition of Ultra High Energy Cosmic RaysR. Abbasi, Andrej Filipčič, Ahmed Saleh, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2016, published scientific conference contribution Keywords: ultra-high energy cosmic rays (UHECR), UHECR mass composition, Pierre Auger Observatory, Telescope Array, cross-calibration studies
Published in RUNG: 17.11.2016; Views: 5239; Downloads: 0
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