Stability and behavior of the outer array of small water Cherenkov detectors, outriggers, in the HAWC observatory

Abstract

The High-Altitude Water Cherenkov (HAWC) Observatory is used for detecting TeV gamma rays. HAWC is operating at 4,100 meters above level sea on the slope of the Sierra Negra Volcano in the State of Puebla, Mexico, and consists of an array of 300 water Cherenkov detectors (WCDs) covering an area of 22,000 m 2 . Each WCD is equipped with four photomultiplier tubes (PMTs) to detect Cherenkov emission in the water from secondary particles of extensive air-shower (EAS) that are produced in the interactions of primary particles (gamma rays or charged cosmic rays) in the atmosphere. HAWC is able to reconstruct the EAS in the 0.5 to 100 TeV energy range. In order to improve the core determination for events with high energy (> 10 TeV) when the events arrive outside of the HAWC array, the Outrigger upgrade project is adding 350 small WCDs around the main array. These outrigger tanks each have one PMT in a 1.5 meter diameter cylindrical polyethylene tank, covering a total area four times larger than that of the HAWC array. In this work we present leak light testing to identify the stability of the detector and an analysis of deposited charges to understand the detector performance.Stability and behavior of the array of outriggers in the HAWC observatory T. Capistrán

Novel gamma-ray signatures of PeV-scale dark matter

“…The sensitivity of HAWC is anticipated to greatly improve over the next year. A sparse array of smaller WCDs is currently being built around the main HAWC array [66,67], leading to an improvement in sensitivity of a factor of four at energies above tens of TeV. This will also have the effect of significantly reducing the energy and flux systematics for these very high-energy gamma rays.…”