Bulletin of the American Physical Society
APS April Meeting 2019
Volume 64, Number 3
Saturday–Tuesday, April 13–16, 2019; Denver, Colorado
Session G08: Cosmic-ray Spectrum and Composition |
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Sponsoring Units: DAP Chair: Tonia Venters, NASA GSFC Room: Sheraton Governor's Square 10 |
Sunday, April 14, 2019 8:30AM - 8:42AM |
G08.00001: Recent results from the Pierre Auger Observatory Fred Sarazin Ultra-High Energy Cosmic-Rays (UHECRs - E>1018eV) lie at the very end of the cosmic-ray spectrum. Their nature and origin remain largely unknown, and their study is made difficult, in part because of the very low flux impinging on Earth's atmosphere. The leading UHECR experiment in the southern hemisphere is the Pierre Auger Observatory, located in the Mendoza province of Argentina. The Observatory consists of an array of 1660 water Cherenkov detectors spread over 3000 km2 and of a collection of 27 fluorescence telescopes located on its outskirt to study the properties of the extensive air showers induced by the UHECRs in the atmosphere. A selection of recent results obtained by the Observatory will be presented in this paper. |
Sunday, April 14, 2019 8:42AM - 8:54AM |
G08.00002: Energy Spectrum Measured by the Telescope Array Experiment Dmitri Ivanov, Dmitri Ivanov Telescope Array (TA) is the largest cosmic ray detector in the Northern hemisphere measuring cosmic rays of energies from 3 PeV to 100 EeV and higher. Combined TA energy spectrum consists of two parts: spectrum measured by the main TA surface detector array and the spectrum measured by the TA low energy extension detector (TALE). We present a combined TA and TALE spectrum, compare the result with other experiments, and discuss anisotropies seen in the TA spectrum at the highest energies. |
Sunday, April 14, 2019 8:54AM - 9:06AM |
G08.00003: The Cosmic Ray Energy Spectrum above 0.1 EeV measured by the Telescope Array and TALE Fluorescence Telescopes JiHee Kim The Telescope Array (TA), deployed in the desert of central Utah, is the largest hybrid cosmic ray detector in the Northern hemisphere. It was initially designed to observe ultra high energy cosmic rays with energies >1019 eV, TA has added an extension, known as the Telescope Array Low-energy Extension (TALE), to lower the experiment's energy threshold by installing high elevation angle telescopes and a dense graded array of surface detectors to the existing main array. It allows us to study cosmic rays in 1015.3-1018.3 eV energy range. The observatory now consists of 48 fluorescence telescopes and a graded array of 610 surface detectors spread over ~750 km2. The fluorescence telescopes observe the longitudinal development of an extensive air shower induced by a cosmic ray, by detecting the scintillation light as the shower develops. Meanwhile, the array of surface detectors measures the lateral distribution of particles reaching the Earth's surface. With TALE extension, the TA Middle Drum site has a field of view 114° in azimuth and 3-59° in elevation. In this work, I will present a measurement of energy spectrum in the energy range of 1017.2-1019.0 eV using fluorescence data collected by the TA and TALE telescopes. |
Sunday, April 14, 2019 9:06AM - 9:18AM |
G08.00004: Composition of Ultra High Energy Cosmic Rays observed by Telescope Array William Hanlon The composition of ultra high energy cosmic rays (UHECRs) with energies in excess of 1018 eV is still unclear over one hundred years after the Nobel prize winning discovery of cosmic rays by Victor Hess in 1912. Evolution of UHECR composition with energy provides important clues as to their origins and allows physicists to rule out theories about their sources, methods of acceleration, and modes of propagation. Questions about the origin of spectral features such as the ankle and the GZK cutoff will be answered by fully understanding the composition of UHECRs. Telescope Array (TA) utilizes hundreds of surface detectors (SDs) constructed with plastic scintillator and dozens of highly light sensitive fluorescence detectors (FDs) to record the passage of extensive air showers in the atmosphere caused by the collision of UHECR primaries and air molecules in the upper atmosphere. TA can measure UHECR mass in a statistical manner by recording energy and depth of air shower maximum, Xmax, for many air showers. TA has collected nine years of high quality Xmax data which will be presented. TA can measure composition through several different analyses, these methods will also be discussed including a new technique which does not record Xmax utilizing machine learning algorithms and SDs. |
Sunday, April 14, 2019 9:18AM - 9:30AM |
G08.00005: Constraints on UHECR sources and their environments, from fitting UHECR spectrum and composition, and neutrinos and gamma-rays. Marco S Muzio, Glennys R Farrar, Michael Unger We perform high-precision joint fitting of the Auger extragalactic spectrum and composition with IceCube astrophysical neutrino spectrum and upper limits, and Fermi-LAT extragalactic gamma-ray spectrum to constrain the properties of UHECR sources, the source environments, source evolution and distance to nearest source. At present, the largest source of uncertainty comes from LHC-tuned hadronic event generators, limiting the ability to derive decisive conclusions on all of the above topics. Nonetheless, we can obtain interesting constraints on UHECR, neutrino and gamma-ray sources. |
Sunday, April 14, 2019 9:30AM - 9:42AM |
G08.00006: SuperTIGER Abundances of Galactic Cosmic-Rays for the Charge Interval Z=41-56 Nathan Elliot Walsh On December 8, 2012 the SuperTIGER (Super Trans-Iron Galactic Element Recorder) instrument was launched from Williams Field, Antarctica on a long-duration balloon flight that lasted 55 days and maintained a mean altitude of 125,000 feet. SuperTIGER measured the relative abundances of Galactic cosmic-ray nuclei with high statistical precision and well resolved individual element peaks from Neon to Zirconium (charges Z=10-40). SuperTIGER also made exploratory measurements of the relative abundances up to Barium (Z=56). Although the statistics are low for elements heavier than Zirconium, we will show how the relative abundances of charges Z=41-56 compare to those reported by HEAO3-HNE during 1979-81. The relative abundances of elements Zirconium through Neodymium (Z=60) are of particular interest because they are likely formed both by supernova explosions and by binary neutron star mergers. A well resolved measurement of this range of elements can constrain the contributions to the Galactic cosmic-ray composition from both of these possible sources. |
Sunday, April 14, 2019 9:42AM - 9:54AM |
G08.00007: Three Years of CALET Ultra Heavy Cosmic Ray Observations Brian F Rauch, W Robert Binns The CALorimetric Electron Telescope (CALET) has been collecting data on the International Space Station (ISS) since shortly after its launch in August 2015. Its main calorimeter (CAL), designed to measure the fluxes of the highest energy cosmic-ray electrons, has also made excellent measurements of cosmic-ray (CR) nuclei and gamma rays. CAL has measured energy spectra as well as secondary to primary ratios of the more abundant CR nuclei through 26Fe, and it has the demonstrated dynamic range to measure CR nuclei from 1H to 40Zr. A high duty cycle (~90%) ultra-heavy cosmic-ray (UHCR) trigger provides an expanded geometric acceptance that is ~6× that for events fully contained by the CAL, which will collect in 5 years a UHCR data set with statistics comparable to that so far collected by the balloon-borne SuperTIGER instrument. Preliminary CALET results are in reasonable agreement with SuperTIGER relative abundances of even charge UHCR nuclei in a similar energy range, and both these measurements are complemented by the ~1/3 smaller lower-energy space-based ACE-CRIS measurements. Here we present the state of the analysis of ~3 years of this CALET UHCR data set and plans for future analysis steps. |
Sunday, April 14, 2019 9:54AM - 10:06AM |
G08.00008: Measurements of Nuclei Fluxes in Cosmic Rays with CALET Yosui Akaike The CALorimetric Electron Telescope (CALET) has been measuring high-energy cosmic rays on the International Space Station since October 2015. The scientific objectives addressed by the mission are the measurement of the electron spectrum in the TeV region as well as the measurement of nuclei fluxes from proton to iron in the range from a few tens of GeV to the PeV scale to investigate the details of their origin and propagation in the galaxy. The features of the instrument include excellent charge resolution based on the segmented scintillator paddles and scintillating fibers and very good energy resolution provided by its thick calorimeter. The details about the analysis procedure of nuclei measurements and preliminary results of energy spectra for nuclei upto 100 TeV and boron-to-carbon flux ratio with three years of operations will be presented. |
Sunday, April 14, 2019 10:06AM - 10:18AM |
G08.00009: Telescope Array 10 Year Fluorescence Detector Monocular Analysis Greg Furlich The Telescope Array (TA) cosmic ray observatory in Millard County, Utah has passed 10 years of fluorescence detector operation, collecting information on the highest energy particles in the universe interacting with Earth's atmosphere. With the increased statistics of over 10 years of data, TA is also working on reducing the systematic uncertainties of cosmic ray analyses. One such systematic uncertainty is the identification of data with good weather using the fluorescence detector's field-of-view snapshots in a Recurrent Convolution Neural Network (RCNN) classification model. TA is working to update the monocular energy spectrum with 10 years of data with a better understanding of these systematic errors. |
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