Limits on the Multi-TeV Cosmic Ray Electron Flux from CREST (Cosmic Ray Electron Synchrotron Telescope)

The CREST instrument is designed to detect cosmic electrons at energy above 2 TeV, which would likely originate in the local Galactic neighborhood owing to their rapid energy loss rates during propagation. CREST detects electrons through their geo-synchrotron x-ray emission, which at these energies is emitted along the direction of electron travel, resulting in a co-linear, isochronous arrangement of x-ray hits in the detector. To observe this signature, an array of 1024 BaF2 crystal detectors was built, surrounded by veto plastic scintillators to guard against chance alignments of charged particles in air showers. This instrument was flown on a high-altitude balloon for 10 days in Antarctica during the 2011/2012 season. In this paper the analysis of this data is described, a limit is placed on the number of electrons with energies above 15 TeV observed during the flight, and the principal backgrounds to their signature are characterized.