231. Telescope Array Composition SummaryW. Hanlon, Jon Paul Lundquist, 2018, published scientific conference contribution Abstract: Ultra high energy cosmic ray (UHECR) chemical composition is
important to resolving questions about the locations of UHECR
sources and propagation models. Because composition can only be
deduced by a process of statistical inference via the observation of air shower maxima (Xmax), UHECR observatories with large data
collection rates must be employed to reduce statistical
fluctuations. Telescope Array (TA), the largest cosmic ray
observatory in the Northern Hemisphere, is designed to answer the
question of UHECR composition, as well as other important features
of cosmic ray flux, by combining a large array of over 500
scintillation surface detectors spread over 700 km^2, and three
fluorescence detector stations overlooking the array. With eight
years of data recorded, results of the measurements of UHECR
composition will be presented. UHECR composition is traditionally
measured by comparing the first and second moments of the
distributions of shower maxima, which evolves with energy, between
data and simulations. Reducing statistical fluctuations in the data
helps to distinguish between different primary elements in the
flux. In the current generation of cosmic ray observatories, UHECR
data sets are large enough, and statistical uncertainties are now
small enough, that we can safely distinguish between very light
primary source flux (i.e., protons) and heavy flux (i.e.,
iron). Reducing systematic uncertainties is also important though,
since large systematic shifts in air shower maxima will influence
the interpretation of the data when compared to models. TA therefore employs different methods of measuring Xmax, including stereo air fluorescence, air fluorescence-surface counter hybrid, and a new technique using only surface counters. Updated results of TA hybrid composition among the different methods are presented using up to eight years of data. Agreement among all TA hybrid composition results are shown as well as detailed systematic errors which can be further explored by comparing composition results of the different measurement methods. Comparison of TA Xmax data are
compared to different composition models as well. Keywords: UHECR, Cosmic rays, composition Published in RUNG: 29.04.2020; Views: 2554; Downloads: 83 Full text (499,33 KB) |
232. Evidence of Intermediate-Scale Energy Spectrum Anisotropy of Cosmic Rays E>10^19.2 eV with the Telescope Array Surface DetectorJon Paul Lundquist, published scientific conference contribution abstract Abstract: Evidence of an intermediate-scale energy spectrum anisotropy has been found in the arrival directions of ultra-high energy cosmic rays of energies above 10^19.2 eV in the northern hemisphere, using 7 years of Telescope Array (TA) surface detector (SD) 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 139 R.A., 45 Dec., and has a deficit of events with energies 10^19.210^19.75 eV. The post-trial probability of this energy anisotropy, appearing by chance anywhere on an isotropic sky, is found by Monte Carlo
(MC) simulation to be 9x10^-5 (3.74 σ_global). Keywords: UHECR, cosmic rays, energy spectrum, anisotropy Published in RUNG: 29.04.2020; Views: 2681; Downloads: 82 Link to file This document has many files! More... |
233. Evidence of Intermediate-Scale Energy Spectrum Anisotropy in the Northern Hemisphere from Telescope ArrayJon Paul Lundquist, 2018, published scientific conference contribution Abstract: Evidence of an energy dependent intermediate-scale anisotropy has been found in the arrival directions of ultra-high energy cosmic rays in the northern hemisphere, using 7 years of TA surface detector data. The previously reported ``hot spot" excess E ≥ 10^19.75 EeV is found to correspond to a deficit, or ``cold spot," of events for 10^19.2≤ E < 10^19.75 EeV. This feature suggests energy dependent magnetic deflection of cosmic-rays. The global post-trial significance of the energy spectrum deviation is found to be 3.74σ. Keywords: UHECR, cosmic rays, energy spectrum, anisotropy, magnetic deflection Published in RUNG: 28.04.2020; Views: 2802; Downloads: 79 Full text (4,87 MB) |
234. Telescope Array Hot/Coldspot Study – Intermediate Scale AnisotropyJon Paul Lundquist, published scientific conference contribution abstract Abstract: Indications of energy dependent intermediate scale anisotropy has been found in the arrival directions of ultra high energy cosmic rays with energies above 20 EeV in the northern hemisphere, using 7 years of TA surface detector data. The previously reported “hotspot‘” excess for E>57 EeV is found to correspond to a deficit, or “coldspot ”, of events for energies 2057 EeV has a Li Ma statistical significance of 4.62σ, and the deficit for energies 20Keywords: cosmic rays, energy spectrum, anisotropy, magnetic deflection Published in RUNG: 28.04.2020; Views: 2799; Downloads: 0 This document has many files! More... |
235. Updated Results on the UHECR Hotspot Observed by the Telescope Array ExperimentK. Kawata, Jon Paul Lundquist, 2019, published scientific conference contribution Abstract: The Telescope Array Experiment has observed an indication of intermediate-scale anisotropy in the UHECR arrival directions, called the Hotspot, with E>57 EeV around the Ursa Major using the first 5-year data during a period between May 2008 and May 2013 collected by the TA surface detector array. The chance probability of this hotspot in an isotropic cosmic-ray sky was calculated to be 3.4σ (post trial). In this paper, we will report on an update of this result using the 11-year data collected by the TA surface detectors with more than doubled exposure since the first publication. Keywords: UHECR, cosmic rays, anisotropy Published in RUNG: 28.04.2020; Views: 2547; Downloads: 80 Full text (934,91 KB) |
236. Track Reconstruction for ISS-CREAM Resulting in Improved Energy and Charge ResolutionsJon Paul Lundquist, 2019, published scientific conference contribution Abstract: Cosmic Ray Energetics And Mass for the International Space Station (ISS-CREAM) has taken 1.5 years of direct measurements of high-energy cosmic ray (HECR) particles for energies from 10^12 to 10^15 eV. HECR particle identification is significantly improved by tracking particle-detector interactions from the calorimeter (CAL) back to the Silicon Charge Detector (SCD) for charge determination. A track finding algorithm resistant to such issues as particle multiplicity, backscatter, and electronic noise will be outlined. Also, shown is the energy resolution improvement, and the resulting all particle spectrum, provided by ensuring good particle tracks. This allows ISSCREAM to investigate how the energy distributions evolve, for protons all the way to iron nuclei, and will provide important information for models of galactic sources and HECR propagation. Keywords: cosmic rays, high energy, detectors, track fitting Published in RUNG: 28.04.2020; Views: 2739; Downloads: 84 Full text (481,98 KB) |
237. 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: 2650; Downloads: 82 Full text (4,92 MB) |
238. Supergalactic Structure of Multiplets with the Telescope Array Surface DetectorJon Paul Lundquist, P. Sokolsky, 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. Keywords: UHECR, cosmic rays, energy spectrum, anisotropy, large-scale structure, magnetic deflection Published in RUNG: 28.04.2020; Views: 2860; Downloads: 151 Full text (1,38 MB) |
239. Improving Particle Identification with Resistant Track Finding for the ISS-CREAM CalorimeterJon Paul Lundquist, published scientific conference contribution abstract Abstract: Moving from Antarctic balloons to the International Space Station the Cosmic Ray Energetics And Mass detector (ISS-CREAM) has begun taking the highest energy direct measurements of cosmic ray (CR) particles ever attempted. ISS-CREAM will investigate how the energy distributions evolve, for protons all the way to iron nuclei, and will provide important information for models of galactic sources and CR propagation. The CR particle identification can be significantly improved by tracking particle-detector interactions from the calorimeter (for energy measurement) back to the Silicon Charge Detector for atomic number determination. A track finding algorithm resistant to such issues as particle multiplicity, backscatter, and noise is outlined. Keywords: cosmic rays, high energy, track finding Published in RUNG: 28.04.2020; Views: 2968; Downloads: 0 This document has many files! More... |
240. Supergalactic Structure of Energy-Angle CorrelationsJon Paul Lundquist, P. Sokolsky, 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. Keywords: Cosmic rays, UHECR, energy spectrum, magnetic deflection, large-scale structure, supergalactic, multiplets Published in RUNG: 27.04.2020; Views: 2739; Downloads: 85 Full text (1,66 MB) |