Luminescence of water or ice as a new detection method for magnetic monopoles

Abstract

Abstract. Cosmic ray detectors use air as a radiator for luminescence. In water and ice, Cherenkov light is the dominant light producing mechanism when the particle's velocity exceeds the Cherenkov threshold, approximately three quarters of the speed of light in vacuum. Luminescence is produced by highly ionizing particles passing through matter due to the electronic excitation of the surrounding molecules. The observables of luminescence, such as the wavelength spectrum and decay times, are highly dependent on the properties of the medium, in particular, temperature and purity. The results for the light yield of luminescence of previous measurements vary by two orders of magnitude. It will be shown that even for the lowest measured light yield, luminescence is an important signature of highly ionizing particles below the Cherenkov threshold. These could be magnetic monopoles or other massive and highly ionizing exotic particles. With the highest observed efficiencies, luminescence may even contribute significantly to the light output of standard model particles such as the PeV IceCube neutrinos. We present analysis techniques to use luminescence in neutrino telescopes and discuss experimental setups to measure the light yield of luminescence for the particular conditions in neutrino detectors.

Probing particle physics with IceCube

“…37). 35 Light yield for the different radiation mechanisms of magnetic monopoles [313]. For comparison the direct Cherenkov light emitted by a minimum ionising muon is shown.…”

“…Pending further laboratory measurements in ice and water [323], the efficiency of luminescence photon production per deposited energy is in the range of dN γ /dE = 0.2 γ/MeV and 2.4 γ/MeV [324,325]. Even for the lower plausible light yield, luminescence is a viable signature due to the high excitation of the medium induced by a monopole [313].…”

“…Instead variables describing the topology, smoothness, and time distribution of the events are processed in a Boosted Decision Tree (BDT) machine learning [320]. (iii) Searching for mildly relativistic monopoles using luminescence light can be performed using analysis techniques that combine the non-relativistic reconstructed particle velocity and the continuous but dim light production of a through-going track in the detector [313,318]. log 10 γ Fig.…”

Searches for Magnetic Monopoles and Other Stable Massive Particles

“…Concerning ice and water, the results for the light yield of luminescence of different measurements vary by large factors: a summary of the status of observations is in [41]. At present, the contribution of this effect for the detection of Ms is not completely understood and not used in published results (see §9).…”

Ongoing magnetic monopole searches with IceCube

“…In contrast to muon and neutrino signatures seen by IceCube, they are relatively dim. A special filter, the Monopole filter [11], is in place in IceCube to select these events; it selects candidate events at a rate of 31 Hz. The filter works by placing straight cuts on different variables like the reconstructed velocity, reconstruction quality, and event duration.…”