Y. Ho

Measurement of the cosmic-ray energy spectrum and composition from 1017 to 1018.3 eV using a hybrid technique

We study the spectrum and average mass composition of cosmic rays with primary energies between 10^{17} eV and 10^{18} eV using a hybrid detector consisting of the High Resolution Flys Eye (HiRes) prototype and the MIA muon array. Measurements have been made of the change in the depth of shower maximum as a function of energy. A complete Monte Carlo simulation of the detector response and comparisons with shower simulations leads to the conclusion that the cosmic ray intensity is changing f rom a heavier to a lighter composition in this energy range. The spectrum is consistent with earlier Flys Eye measurements and supports the previously found steepening near 4 \times 10^{17} eV .

Measurement of the Cosmic Ray Energy Spectrum and Composition from 10^{17} to 10^{18.3} eV Using a Hybrid Fluorescence Technique

We study the spectrum and average mass composition of cosmic rays with primary energies between 10^{17} eV and 10^{18} eV using a hybrid detector consisting of the High Resolution Flys Eye (HiRes) prototype and the MIA muon array. Measurements have been made of the change in the depth of shower maximum as a function of energy. A complete Monte Carlo simulation of the detector response and comparisons with shower simulations leads to the conclusion that the cosmic ray intensity is changing f rom a heavier to a lighter composition in this energy range. The spectrum is consistent with earlier Flys Eye measurements and supports the previously found steepening near 4 \times 10^{17} eV .

The prototype high-resolution Fly's Eye cosmic ray detector

Abstract The High-Resolution Flys Eye (HiRes) is an observatory for the highest energy cosmic rays. It detects the nitrogen fluorescence light induced by the passage of giant cosmic ray extensive air showers through the atmosphere. A two-site prototype of the observatory was operated from September 1994 to November 1996. In this paper we describe the components of that detector, and the procedures used to calibrate the detector and characterise the atmosphere. Data collected by the HiRes prototype are being used for physics studies, including an analysis of the cosmic ray mass composition in the energy range from 10 17 to 10 18 eV .

A measurement of the average longitudinal development profile of cosmic ray air showers between 1017 and 1018 eV

The average extensive air shower longitudinal development profile as a function of shower age in the energy range from 10

Geometrical reconstruction with the High Resolution Fly's Eye prototype cosmic ray detector

^{17}

Measurement of the circulating muon flux in the Fermilab Debuncher ring

to 10

Radio-controlled xenon flashers for atmospheric monitoring at the HiRes cosmic ray observatory

^{18}

Status of the High Resolution Fly's Eye Detector: Operation and Installation

eV is measured using data from the hybrid HiRes/MIA experiment. An angular bin signal based Cerenkov light component subtraction method and a shower maximum fitting method using a local parabolic function are used to correct and normalize the data. The Gaisser-Hillas and Greisen functions work equally well for describing the shower profile. The Gaussian function is a poor fit. A simple scale-free function is proposed and fits the data equally well. The best-fit parameters for the above functions are determined.Abstract The average extensive air shower longitudinal development profile is measured. Events between 10 17 and 10 18 eV recorded by the HiRes/MIA hybrid experiment are used for the average profile. Several functional forms are examined using this average profile. The best-fit parameters for the above functions are determined.

Atmospheric Monitoring for Fluorescence Detector Experiments

Abstract The High Resolution Flys Eye EHE cosmic ray detector (HiRes) was operated for over two years (prior to November 1996) in a two-site prototype configuration. This paper describes the development and testing of an event reconstruction method for extensive air showers (EAS) viewed in coincidence by both sites (stereo viewing). The reconstruction accuracy was directly measured through the use of a UV laser mounted on a telescope that generated airshower-like events with known geometries. For events observed with stereo opening angles greater than about 10° (most events) the median error in the reconstructed laser direction was 0.4° with 95% of events being reconstructed with errors of less than 0.9° (which degrade to 0.8° and 1.8°, respectively, for smaller opening angles). A limited investigation of the likely performance of the HiRes Stage 1.0 detector was undertaken. Reconstruction accuracy is likely to be only slightly degraded compared with the prototype results.

Stereo Reconstruction of EAS with the Hires Detector

Using a novel experimental technique, we have measured the flux of pions, electrons, muons, and antiprotons which are injected into and circulate in the Fermilab Debuncher ring. The experimental technique relied upon the use of a nondestructive, rf pickup to measure the bunch structure of the beam on a turn-by-turn basis. The measured muon to antiproton ratio is μ−/p = 1.0±0.2, and the ratio of muons to protons on target is μ−/poT = 2.0±0.4×10−5.