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21.
Telescope Array Hot/Coldspot Study – Intermediate Scale Anisotropy
J. P. 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 20Found in: osebi
Keywords: cosmic rays, energy spectrum, anisotropy, magnetic deflection
Published: 28.04.2020; Views: 1479; Downloads: 0
.pdf Fulltext (2,25 MB)

22.
Updated Results on the UHECR Hotspot Observed by the Telescope Array Experiment
J. P. Lundquist, K. Kawata, 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.
Found in: osebi
Keywords: UHECR, cosmic rays, anisotropy
Published: 28.04.2020; Views: 1322; Downloads: 49
.pdf Fulltext (934,91 KB)

23.
Track Reconstruction for ISS-CREAM Resulting in Improved Energy and Charge Resolutions
J. P. 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.
Found in: osebi
Keywords: cosmic rays, high energy, detectors, track fitting
Published: 28.04.2020; Views: 1548; Downloads: 53
.pdf Fulltext (481,98 KB)

24.
TA Anisotropy Summary
J. P. Lundquist, K. Kawata, 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.
Found in: osebi
Keywords: cosmic radiation, UHE detector, fluorescence detector, surface, Telescope Array Experiment, anisotropy, experimental results
Published: 28.04.2020; Views: 1567; Downloads: 51
.pdf Fulltext (1,88 MB)

25.
Covering the celestial sphere at ultra-high energies: Full-sky cosmic-ray maps beyond the ankle and the flux suppression
J. P. Lundquist, J. Biteau, 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.
Found in: osebi
Keywords: UHECR, cosmic rays, anisotropy, Telescope Array, Pierre Auger Observatory
Published: 28.04.2020; Views: 1422; Downloads: 53
.pdf Fulltext (4,92 MB)

26.
Evidence of Intermediate-Scale Energy Spectrum Anisotropy of Cosmic Rays E>10^19.2 eV with the Telescope Array Surface Detector
J. P. 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).
Found in: osebi
Keywords: UHECR, cosmic rays, energy spectrum, anisotropy
Published: 29.04.2020; Views: 1461; Downloads: 55
.pdf Fulltext (408,40 KB)

27.
Telescope Array Composition Summary
J. P. Lundquist, W. Hanlon, 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.
Found in: osebi
Keywords: UHECR, Cosmic rays, composition
Published: 29.04.2020; Views: 1299; Downloads: 51
.pdf Fulltext (499,33 KB)

28.
Telescope Array anisotropy summary
J. P. Lundquist, M. Fukushima, 2018, published scientific conference contribution

Abstract: The Telescope Array has accumulated the largest UHECR data set in the Northern hemisphere. We make use of these data to search for large- and small-scale anisotropy of UHECR arrival directions. At small angular scales, we report an update on searches for clustering of events and on correlations with various classes of putative sources. At large angular scales, we revisit, with the new data and with new tests, the localized excess of events known as the TA “hot spot”. We review some other studies of the arrival directions and corresponding implications for the nature of UHECR sources.
Found in: osebi
Keywords: UHECR, cosmic rays, anisotropy
Published: 29.04.2020; Views: 1344; Downloads: 55
.pdf Fulltext (581,87 KB)

29.
A systematic uncertainty on the energy scale of the Telescope Array fluorescence detectors
J. P. Lundquist, T. Fujii, 2018, published scientific conference contribution

Abstract: The Telescope Array experiment (TA) is the largest cosmic-ray detector in the northern hemi-sphere and consists of a surface detector (SD) array, plus three fluorescence detector (FD) stations overlooking the SD. The large field-of-view of an FD allows for reconstruction of the air-shower development in the atmosphere by imaging ultra-violet fluorescence light from atmospheric nitrogen excited by UHECRs. In estimation of the primary energy it is necessary to add to the calorimetric energy observed by the FD a “missing energy”, meaning the fraction of the primary energy that is not deposited by charged particles in the air. We report on the measurement of the missing energy from observed data collected by the TA FD and TA SD, independently of Monte Carlo simulations, using a technique pioneered by the Pierre Auger Observatory. We also address the effect on the energy scale attributed to fluorescence yield parameters.
Found in: osebi
Keywords: UHECR, cosmic rays, energy spectrum
Published: 29.04.2020; Views: 1368; Downloads: 51
.pdf Fulltext (4,74 MB)

30.
Energy-position correlation anisotropy of ultra-high energy cosmic rays with Telescope Array Data
J. P. Lundquist, published scientific conference contribution abstract

Abstract: Indication of an 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 20Found in: osebi
Keywords: UHECR, energy spectrum, anisotropy, magnetic deflection
Published: 29.04.2020; Views: 1456; Downloads: 0
.pdf Fulltext (1,84 MB)

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