Bulletin of the American Physical Society
APS April Meeting 2018
Volume 63, Number 4
Saturday–Tuesday, April 14–17, 2018; Columbus, Ohio
Session H15: Ultra High Energy Cosmic Rays |
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Sponsoring Units: DAP Chair: Tracy Slatyer, MIT Room: B230-231 |
Sunday, April 15, 2018 10:45AM - 10:57AM |
H15.00001: Ultra High Energy Cosmic Ray Composition Observed by Telescope Array in Hybrid Mode William Hanlon The distribution of nuclear species is a fundamental parameter of models that describe the origin and propagation of ultra high energy cosmic rays (UHECRs), commonly referred to as UHECR composition. Composition affects the shape of the UHECR energy spectrum observed on Earth, limits the maximum distance of propagation due to interactions with the CMB, and provides information about the acceleration mechanisms of their sources. Due to the extremely low flux of cosmic rays with energies $> 10^{15}$ eV, direct measurement of composition is not practical. However, the properties of particle cascades caused by UHECRs interacting in the atmosphere are related to their mass, allowing us to indirectly measure composition using statistical inference. In this talk we will present recent results of $X_{\mathrm{max}}$ measurements by Telescope Array (TA), a very large cosmic ray observatory located in central Utah with a view of the northern hemisphere. Nearly nine years of hybrid $X_{\mathrm{max}}$ data are analyzed and compared to Monte Carlo simulations of UHECRs with energies exceeding $10^{18.2}$ eV. We also calculate and present distributions of $X_{\mathrm{max}}$ and test the compatibility of data with Monte Carlo simulations of four different chemical species. [Preview Abstract] |
Sunday, April 15, 2018 10:57AM - 11:09AM |
H15.00002: Measuring cosmic-ray composition at PeV energies with the IceCube Observatory James Bourbeau, Stefan Westerhoff While cosmic-ray composition has been precisely measured at lower energies, it is still not well known at energies above the knee in the all-particle cosmic-ray spectrum. We present initial measurements of the cosmic-ray composition spectrum at PeV energies using one year of data from the IceCube Observatory. With its surface array and underground muon detector, the IceCube Observatory is capable of simultaneously measuring the total energy of cosmic-ray air showers as well as their muon content, allowing for composition discrimination. [Preview Abstract] |
Sunday, April 15, 2018 11:09AM - 11:21AM |
H15.00003: The Cosmic Ray Energy Spectrum above 0.1 EeV measured by the Telescope Array and TALE Fluorescence Telescopes JiHee Kim The Telescope Array (TA) is the largest cosmic ray detector in the Northern hemisphere. It is deployed in the desert of central Utah. Initially designed to study ultra high energy cosmic rays with energies $>10^{18}$ eV, TA has added an extension to lower the experiment's energy threshold. Known as the Telescope Array Low-energy Extension (TALE), high elevation angle telescopes and a denser graded array of scintillation detectors were added to the main array, allowing us to lower the energy threshold to $\sim10^{15.5}$ eV. The observatory now consists of 48 telescopes and a graded array of 610 scintillators spread over $\sim$750 $\rm{km}^{2}$. The telescopes observe the longitudinal development of a cosmic ray induced extensive air shower by detecting the scintillation light emitted as the shower develops in the atmosphere. Meanwhile, the array of scintillator detectors samples the lateral distribution of particles reaching the Earth's surface. The northern telescope station has the greatest field of view and is closest to the most densely packed portion of the scintillator detector array, making it more sensitive to the low energy range of the spectrum. I will present the energy spectrum made by combining data from the main TA and TALE extension fluorescence telescopes. [Preview Abstract] |
Sunday, April 15, 2018 11:21AM - 11:33AM |
H15.00004: Measurement of the cosmic ray flux spectrum above 300 PeV with the Pierre Auger Observatory Alan Coleman The Pierre Auger Observatory observes the flux of cosmic rays over three decades in energy. This is possible by combining the measurements of a 1500 m and a 750 m surface detector arrays. The energy scale relies on the almost-calorimetric measurements of air showers performed with the fluorescence detector (FD) of the observatory. The precise measurement of the cosmic ray flux above 300 PeV is possible due to the recent improvement to the FD systematics and the increased exposure of the observatory (about 52000 km$^2$ sr yr). The spectrum is presented along with the recent measurements of the cosmic ray ankle and flux suppression. [Preview Abstract] |
Sunday, April 15, 2018 11:33AM - 11:45AM |
H15.00005: Anisotropy Results of the Telescope Array Experiment Dmitri Ivanov We report the results of ultra-high energy cosmic ray anisotropy in the Northern hemisphere obtained using data of the Telescope Array (TA) experiment. TA is located in the desert near Delta, UT, and it consists of a surface detector array of 507 plastic scintillation counters, effectively covering a \textasciitilde 700 km$^{\mathrm{2}}$ area on the ground, which is overlooked by 3 fluorescence detector stations. This work consists of two parts. First, we present the result of the search for EeV protons of Galactic origin in the TA data in 10$^{\mathrm{18.0}}$ to 10$^{\mathrm{18.5\thinspace }}$eV range and place an upper limit on the fraction of the Galactic protons in the TA spectrum. Then we report anisotropies above 10 EeV that are seen in the TA spectrum and in the TA event arrival directions on the sky. Discussion of the TA spectrum anisotropy and a local excess of events above 57 EeV near the direction of Ursa Major, called the ``TA Hot Spot'', will be given. We also compare the TA spectrum with the spectrum measured by the Pierre Auger Observatory in a declination band that is commonly seen by both experiments. [Preview Abstract] |
Sunday, April 15, 2018 11:45AM - 11:57AM |
H15.00006: Observing Ultra-High-Energy Cosmic Rays with a prototype of the Fluorescence detector Array of Single-pixel Telescopes John Farmer Fluorescence detector Array of Single-pixel Telescopes (FAST) is an R\&D project for the next generation of cosmic ray detectors; it addresses the need to instrument a huge area at a low cost to observe the most energetic Ultra-High-Energy Cosmic Rays (UHECRs). FAST features a compact design with four 200\,mm PMTs at the focal plane of a 1.6\,m segmented mirror with an automated DAQ system. As of 2018, we have assembled two iterative prototypes at the Black Rock Mesa site of the Telescope Array (TA) experiment in Utah, demonstrating stable remote operation under high background and stereo observations of UHECR events, artificial light sources, and ultraviolet laser shots. We discuss UHECR measurements and calibrations for these prototypes, compare with artificial traces generated by Monte Carlo and ray-tracing simulations, and discuss the possibility of using FAST to cross-calibrate the energy scales of the two largest UHECR observatories, the Telescope Array experiment and the Pierre Auger Observatory. [Preview Abstract] |
Sunday, April 15, 2018 11:57AM - 12:09PM |
H15.00007: Recent Results from the Auger@TA Cross-calibration Project Sean Quinn The Pierre Auger Observatory (Auger) and Telescope Array Project (TA) are hybrid cosmic ray observatories operating in the southern and northern hemisphere, respectively. In both experiments the majority of data are generated from the surface-detector (SD) array. Auger and TA have implemented different SD station designs, giving them different sensitivities to extensive air-shower components. We seek to understand and cross-validate these complementary detectors on a hardware level using an \textit{in-situ} approach where co-located SD stations observe the same air showers. We present the technical details for installing the detectors, data acquisition, and the analysis of signals for this first phase of the program, in operation for over one year. Integrated signals are directly compared between the SD stations, and also examined as a function of zenith angle. For a subsample of events we compare a suite of reconstructed air-shower parameters to geometrically equivalent simulations of our setup in the field. Characterizing and understanding any differences between data and simulation will be important for taking full advantage of future planned upgrades to both experiments, especially in the context of composition measurements. [Preview Abstract] |
Sunday, April 15, 2018 12:09PM - 12:21PM |
H15.00008: The Non-Imaging CHErenkov (NICHE) Array: A TA/TALE extension using Cherenkov radiation to measure Cosmic Ray Composition to sub-PeV energies Douglas Bergman, John Krizmanic, Tareq Abu-Zayyad, Yoshiki Tsunesada Co-sited with the Telescope Array (TA) Low Energy (TALE) extension, the Non-Imaging CHErenkov (NICHE) Array will measure the flux and nuclear composition evolution of cosmic rays (CRs) from below 1 PeV to 1 EeV in its eventual full deployment. NICHE will co-measure CR air showers with TA/TALE and will initially be deployed to observe events simultaneously with the TALE telescopes acting in imaging-Cherenkov mode, providing the first hybrid-Cherenkov (simultaneous imaging and non-imaging Cherenkov) measurements of CRs in the Knee region of the CR energy spectrum. NICHE uses easily deployable detectors to measure the amplitude and time-spread of the air-shower Cherenkov signal to achieve an event-by-event measurement of $X_{\rm max}$ and energy, each with excellent resolution. A prototype array of 15 first-generation detectors called j-NICHE has been deployed at the TA/TALE site. In this talk, the NICHE design, array performance, j-NICHE status and initial data analysis will be discussed. [Preview Abstract] |
Sunday, April 15, 2018 12:21PM - 12:33PM |
H15.00009: Diffuse Gamma-ray and Neutrino Constraints on UHECR sources, for realistic UHECR composition. Marco Muzio, Glennys Farrar, Michael Unger Using a method of tabulated fluxes we have produced high-resolution simulations of the diffuse photon fluxes produced in various CR source models. We show that a mixed-composition model, such as that of Unger, Farrar, and Anchordoqui (UFA, 2015), can fit both the Auger spectrum and composition evolution as well as respect Fermi-LAT limits on the diffuse photon flux. Moreover, we show these models do so without any need for the Earth to be located at a local overdensity of UHECR sources. We also show that Fermi-LAT data in combination with data from IceCube can be used to constrain source conditions in UFA scenarios. [Preview Abstract] |
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