Bulletin of the American Physical Society
APS April Meeting 2016
Volume 61, Number 6
Saturday–Tuesday, April 16–19, 2016; Salt Lake City, Utah
Session U12: High and Ultra High Energy Cosmic Rays |
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Sponsoring Units: DAP Chair: John Belz, University of Utah Room: 250DE |
Monday, April 18, 2016 3:30PM - 3:42PM |
U12.00001: The Cosmic Rays Energy Spectrum observed by the TALE detector Tareq AbuZayyad We report on a cosmic ray energy spectrum measurement by the Telescope Array Low-Energy extension (TALE) fluorescence detector (FD). The TALE FD is an air fluorescence detector which is also sensitive to the Cerenkov light produced by shower particles. Low energy cosmic rays, in the PeV energy range, are detectable by TALE as "Cerenkov Events". Using these events, we measure the energy spectrum from a low energy of ~ 4 PeV to an energy greater than 100 PeV. Starting at around 100 PeV, TALE also observes showers by their fluorescence light; and above this energy fluorescence becomes the dominant light production mechanism by which most showers are observed. The event processing and reconstruction procedures are identical for both low and high energy regions. This allows for treating the Cherenkov events and Fluorescence events as a single data set and thus calculating a single cosmic rays energy spectrum based on this data set, which extends from an energy of ~ 4 PeV to above 1 EeV. In this talk, we will describe the detector, explain the technique, and present results from the measurement of the spectrum in this energy range by the Telescope Array experiment. [Preview Abstract] |
Monday, April 18, 2016 3:42PM - 3:54PM |
U12.00002: The Telescope Array RADAR (TARA) Project and the Search for the Radar Signature of Cosmic Ray Induced Extensive Air Showers. Steven Prohira The TARA (Telescope Array Radar) cosmic ray detector has been in operation since May 2013. It is the most ambitious effort to date to test an idea that originated in the 1940's: that ionization produced by cosmic ray extensive air showers should reflect electromagnetic radiation. The observation of this effect would open the possibility that remote-sensing radar technology could be used to detect and reconstruct extensive air showers, thus increasing the aperture available for the study of the highest-energy cosmic rays. TARA employs a bi-static radar configuration, consisting of a 25 kW, 5 MW ERP transmitter at 54.1 MHz broadcasting across the Telescope Array surface detector. 40 km distant, a set of log-periodic receiver antennas are read out by two independent data acquisition systems employing different techniques to select signals of the form expected for radar targets moving at close to the speed of light. In this talk, we describe the TARA detector and present the first quantitative limits on the radar cross-section of extensive air showers. [Preview Abstract] |
Monday, April 18, 2016 3:54PM - 4:06PM |
U12.00003: Composition of Ultra High Energy Cosmic Rays Observed by Telescope Array in Hybrid Mode William Hanlon The energy spectrum of cosmic rays exhibits several important features such as the knee ($E \sim 10^{15.5}$~eV), ankle ($E \sim 10^{18.7}$~eV), and high energy suppression ($E \sim 10^{19.8}$~eV). Cosmic ray chemical composition is the key to understanding their galactic and extragalactic sources as well as the origin of particle production and acceleration mechanisms. Energy dependent chemical composition is a fundamental input for models of cosmic ray sources and interstellar transport which may lead to competing explanations of the observed spectral features. Understanding composition will therefore allow one to distinguish between the different scenarios of cosmic ray origin, a decades old problem in astrophysics. In this talk we will describe measurements of ultra high energy cosmic ray composition performed by Telescope Array (TA) using $X_{\mathrm{max}}$ measured in extended air showers (EAS) simultaneously observed by the TA surface array and TA fluorescence stations (called hybrid mode). Showers with primary energies above $10^{18}$~eV will be considered. We will also discuss improved methods of comparing the measured composition to EAS models. [Preview Abstract] |
Monday, April 18, 2016 4:06PM - 4:18PM |
U12.00004: Telescope Array UHECR composition measurement via stereoscopic fluorescence observation Thomas Stroman, Douglas Bergman When entering Earth's atmosphere at ultra-high energies, cosmic rays (UHECRs) produce extensive air showers whose longitudinal development is influenced by the incident primary particle's mass. Each longitudinal shower profile reaches its maximum particle count at an atmospheric slant depth $X_{\rm max}$, and the distributions of observed $X_{\rm max}$ values can be compared to those predicted by detailed simulations of the air-shower physics and the detector; accurately simulated compositions that most closely resemble that found in nature will produce the best agreement between predicted and observed $X_{\rm max}$ distributions. This is the basis of composition measurement at the Telescope Array experiment, the largest and most sensitive UHECR detector in the northern hemisphere. At the perimeter of a large surface-detector array are three fluorescence telescope stations, whose overlapping apertures enable high-precision reconstruction of $X_{\rm max}$ from stereoscopic observation of air-shower longitudinal profiles. We present the distribution of $X_{\rm max}$ observed during eight years of operation, and from comparisons with several simulated combinations of composition and high-energy hadronic physics, we show that a low primary mass is favored at $E > 10^{18.2}$ eV. [Preview Abstract] |
Monday, April 18, 2016 4:18PM - 4:30PM |
U12.00005: Uncertainties in model predictions of Xmax Rasha Abbasi, Gordon Thomson Recent measurements at the LHC of the p-p total cross section have provided better constraints to the hadronic models used for cosmic ray air showers simulation. However, uncertainties due to extrapolations from accelerator data up to center of mass of 250 TeV ($3 \times 10^{19}$ eV in a cosmic ray’s lab frame) introduces significant uncertainties in predictions of the depth of shower maximum, called Xmax. In this work we estimate a lower limit on these uncertainties in $< \mathrm {Xmax} > $ among the modern models in use in the field. [Preview Abstract] |
Monday, April 18, 2016 4:30PM - 4:42PM |
U12.00006: Determining the Mass Composition of Cosmic Rays Using Shower Universality Andrea Biscoveanu, Miguel Mostafa The mass composition of ultra-high energy cosmic rays is an important parameter for understanding their origin. Using both fluorescence and surface detectors, The Pierre Auger Observatory measures the depth of shower maximum, $X_{\rm max}$, from which the mass of the primary particle can be inferred. The surface detector measurement of $X_{\rm max}$ is based on the principle of shower universality, and increases the number of cosmic rays by at least a factor of 10 with respect to the fluorescence detector measurement since it is not limited by the duty cycle of the fluorescence telescopes. We present an event-by-event comparison of the $X_{\rm max}$ measurements from both types of detectors for energies above $10^{18.8}$~eV, and a preliminary anisotropy study discriminating by the mass of the primary particle calculated using universality. [Preview Abstract] |
Monday, April 18, 2016 4:42PM - 4:54PM |
U12.00007: NICHE: Using Cherenkov radiation to extend Telescope Array to sub-PeV energies. Douglas Bergman, John Krizmanic, Yoshiki Tsunesada, Tareq Abu-Zayyad, John Belz, Gordon Thomson 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. NICHE will be co-sited with the Telescope Array (TA) Low Energy (TALE) extension, and will observe events simultaneously with the TALE telescopes acting in imaging-Cherenkov mode. This will be 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. First generation detectors are under construction and will form an initial prototype array (j-NICHE) that will be deployed in Summer 2016. In this talk, the NICHE design, array performance, prototype development, and status will be discussed as well as NICHE's ability to measure the cosmic ray nuclear composition as a function of energy. [Preview Abstract] |
Monday, April 18, 2016 4:54PM - 5:06PM |
U12.00008: Tidal frequencies in the spectral analysis of time series muon flux measurements Catherine Feldman, Helio Takai Tidal frequencies are observed in the spectral analysis of time series muon flux measurements performed by the MARIACHI experiment over a period of seven years. The prominent peaks from the frequency spectrum correspond to tidal frequencies $S_1$,$S_2$,$S_3$,$K_1$,$P_1$ and $\Psi_1$ . We will present these results and compare them to the regular density oscillations from balloon sounding data. We interpret the observed data as being the effect of regular atmospheric density oscillations induced by the thermal heating of layers in Earth's atmosphere. As the density of the atmosphere varies, the altitude where particles are produced varies accordingly. As a consequence, the muon decay path elongates or contracts, modulating the number of muons detected at ground level. The role of other tidal effects, including geomagnetic tides, will also be discussed. [Preview Abstract] |
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