Long-term monitoring of the ANTARES optical module efficiencies using $^{40}\mathrm{K}$ decays in sea water

TL;DR

This study analyzes nearly a decade of ANTARES data to monitor optical module efficiencies using $^{40}\mathrm{K}$ decay, revealing a modest 20% efficiency loss and enabling calibration of the detector over time.

Contribution

It introduces a long-term method to track optical module efficiency using natural sea water radioactivity in deep-sea neutrino telescopes.

Findings

20% efficiency loss over 9 years

Effective calibration of optical modules achieved

Stable detector performance demonstrated

Abstract

Cherenkov light induced by radioactive decay products is one of the major sources of background light for deep-sea neutrino telescopes such as ANTARES. These decays are at the same time a powerful calibration source. Using data collected by the ANTARES neutrino telescope from mid 2008 to 2017, the time evolution of the photon detection efficiency of optical modules is studied. A modest loss of only 20% in 9 years is observed. The relative time calibration between adjacent modules is derived as well.