Heavy neutrino decay at SHALON

Abstract

Abstract. The SHALON Cherenkov telescope has recorded over 2 × 10 6 extensive air showers during the past 17 years. The analysis of the signal at different zenith angles has included observations from the sub-horizontal direction Θ = 97• . This inclination defines an Earth skimming trajectory with 7 km of air and around 1000 km of rock in front of the telescope. During a period of 324 hours of observation, after a cut of shower-like events that may be caused by chaotic sky flashes or reflections on the snow of vertical showers, we have detected 5 air showers of TeV energies. We argue that these events may be caused by the decay of a long-lived penetrating particle entering the atmosphere from the ground and decaying in front of the telescope. We show that this particle can it not be a muon or a tau lepton. As a possible explanation, we discuss two scenarios with an unstable neutrino of mass m ≈ 0.5 GeV and cτ ≈ 30 m. Remarkably, one of these models has been recently proposed to explain an excess of electron-like neutrino events at MiniBooNE.

Photons coming from an opaque obstacle as a manifestation of heavy neutrino decays

“…6(a) and 6(b), we show the results as a contour plot for different numbers of events in the plane (m N , U2) for different distances to the obstacle. We consider a generic detector like SHALON [12] with an effective area of 10 m 2 , the solid angle spanned by the obstacle (which is compatible with the field of view of SHALON), and a detection time of 1 year. It is clear that, from the results shown, it is easy to obtain the number of events for different values of the observation time, effective area, and number of detectors,…”

“…We have calculated the photon flux originated by the decay of N 's emerging from an opaque object such as a mountain. These photons would be observable by a ground-based Cherenkov instrument like SHALON [12] or any other gamma-ray detector that could observe the showers initiated by such high-energy photons coming from the direction of the obstacle. We considered different situations of obstacles placed at different distances from the detector.…”

“…In addition, the effective operators presented here allow the N decay to one neutrino plus one photon. This decay channel could account, in a particular parameter region, for some neutrino-related problems such as the MiniBOONE [10,11] and SHALON [12] anomalies. The Majorana neutrino effective phenomenology regarding the relevant Ndecay modes and interactions is treated in Refs.…”