Cerenkov Events Seen by The TALE Air Fluorescence Detector

The Telescope Array Low-Energy Extension (TALE) is a hybrid, Air Fluorescence Detector (FD) / Scintillator Array, designed to study cosmic ray initiated showers at energies above $\sim3\times10^{16}$ eV. Located in the western Utah desert, the TALE FD is comprised of 10 telescopes which cover the elevation range 31-58$^{\circ}$ in addition to 14 telescopes with elevation coverage of 3-31$^{\circ}$. As with all other FD's, a subset of the shower events recorded by TALE are ones for which the Cerenkov light produced by the shower particles dominates the total observed light signal. In fact, for the telescopes with higher elevation coverage, low energy Cerenkov events form the vast majority of triggered cosmic ray events. In the typical FD data analysis procedure, this subset of events is discarded and only events for which the majority of signal photons come from air fluorescence are kept. In this talk, I will report on a study to reconstruct the "Cerenkov Events" seen by the high elevation viewing telescopes of TALE. Monte Carlo studies and a first look at real events observed by TALE look very promising. Even as a monocular detector, the geometrical reconstruction method employed in this analysis allows for a pointing accuracy on the order of a degree. Preliminary Monte Carlo studies indicate that, the expected energy resolution is better than 25$$. It may be possible to extend the low energy reach of TALE to below $10^{16}$ eV. This would be the first time a detector designed specifically as an air fluorescence detector is used as an imaging Cerenkov detector.Comment: Presentation at the DPF 2013 Meeting of the American Physical Society Division of Particles and Fields, Santa Cruz, California, August 13-17, 2013. 5 pages, 2 figure

CPT and Lorentz violation in the electroweak sector

Long ago, Carroll, Field and Jackiw introduced CPT-violation in the photon sector by adding a dimension-3 gauge-invariant term parametrized by a constant four-vector parameter k(AF) to the usual (Maxwell) Lagrangian, deriving an ultra-tight bound from astrophysical data. Here, we will discuss recent work studying the extension of this term to the full electroweak gauge sector of the Standard Model. In the context of the Standard Model Extension, CPT and Lorentz violation arises from two gauge-invariant terms parametrized by the four vectors k(1) and k(2). First we will show how upon spontaneous breaking of the electroweak gauge symmetry these two terms yield Lorentz-violating terms for the photon and the W and Z bosons. As it turns out, the resulting modified dispersion relations for the W bosons yield spacelike momentum for one of its propagating modes at sufficiently large energy. This in turn allows for the possibility of Cherenkov-like W-boson emission by high-energy fermions such as protons, provoking their decay. Analysis of ultra-high-energy cosmic ray data allows for bounding the previously unbound parameter k(2), and, by combination with the ultra-tight bound on k(AF), the parameter k(1).Portuguese Fundacao para a Ciencia e a Tecnologia (FCT) - SFRH/BPD/101403/2014program POPH/FSE New College of Floridainfo:eu-repo/semantics/publishedVersio

Relationship between Extensions and Intensions in Categorization: A Match Made in Heaven?

The present study investigated the relationship between category extension and intension for eleven different semantic categories. It is often tacitly assumed that there is a (strong) extension-intension link. However, a recent study by Hampton and Passanisi (2016) examining the patterns of stable individual differences in concepts across participants called this hypothesis into question. To conceptually replicate their findings, two studies were conducted. We employed a category judgment task to measure category extensions, whereas a property generation (in Study 1) and property judgment task (Study 2) were used to measure intensions. Using their method, that is, correlating extension and intension similarity matrices, we found non-significant correlations in both studies, supporting their conclusion that similarity between individuals for extensional judgments does not map onto similarity between individuals for intensional judgments. However, multi-level logistic regression analyses showed that the properties a person generated (Study 1) or endorsed (Study 2) better predicted her own category judgments compared to other people’s category judgments. This result provides evidence in favor of a link between extension and intension at the subject level. The conflicting findings, resulting from two different approaches, and their theoretical repercussions are discussed.status: accepte

SimProp: a Simulation Code for Ultra High Energy Cosmic Ray Propagation

A new Monte Carlo simulation code for the propagation of Ultra High Energy Cosmic Rays is presented. The results of this simulation scheme are tested by comparison with results of another Monte Carlo computation as well as with the results obtained by directly solving the kinetic equation for the propagation of Ultra High Energy Cosmic Rays. A short comparison with the latest flux published by the Pierre Auger collaboration is also presented.Comment: 19 pages, 12 eps figures, version accepted for publication in JCA