Sterile neutrinos as a possible explanation for the upward air shower events at ANITA

Guo-Yuan Huang

doi:10.1103/physrevd.98.043019

Guo-Yuan Huang

Open Access

https://doi.org/10.1103/physrevd.98.043019

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Abstract

The ANITA experiment has observed two unusual upgoing air shower events which are consistent with the $\tau$-lepton decay origin. However, these events are in contradiction with the standard neutrino-matter interaction models as well as the $\rm EeV$ diffuse neutrino flux limits set by the IceCube and the cosmic ray facilities like AUGER. In this paper, we have reinvestigated the possibility of using sterile neutrino hypothesis to explain the ANITA anomalous events. The diffuse flux of the sterile neutrinos is less constrained by the IceCube and AUGER experiments due to the small active-sterile mixing suppression. The quantum decoherence effect should be included for describing the neutrino flux propagating in the Earth matter, because the interactions between neutrinos and the Earth matter are very strong at the EeV scale. After several experimental approximations, we show that the ANITA anomaly itself is able to be explained by the sterile neutrino origin, but we also predict that the IceCube observatory should have more events than ANITA. It makes the sterile neutrino origin very unlikely to account for both of them simultaneously. A more solid conclusion can be drawn by the dedicated ANITA signal simulations.

Highlights

The cosmic rays with an energy around the GreisenZatsepin-Kuzmin (GZK) cutoff (∼50 EeV) would be strongly suppressed due to the interactions with the cosmic microwave background [1,2], i.e., p þ γCMB → p ðor nÞ þ nπ, p þ γCMB → Δþð1232Þ → p þ π0 ðor n þ πþÞ, where n is the total number of the produced π’s
In 2016, the Antarctic Impulsive Transient Antenna (ANITA) experiment has reported one unusual steeply upward-pointing cosmic ray event 3985267 with a shower energy around 0.6 EeV during the ANITA-I flight [5]. This shower event could be generated by the decay of a τ lepton, which is emerging from the surface of the ice with the zenith angle around
We have reinvestigated the possibility of using sterile neutrino origin to explain the ANITA anomalous events

Summary

INTRODUCTION

The cosmic rays with an energy around the GreisenZatsepin-Kuzmin (GZK) cutoff (∼50 EeV) would be strongly suppressed due to the interactions with the cosmic microwave background [1,2], i.e., p þ γCMB → p ðor nÞ þ nπ, p þ γCMB → Δþð1232Þ → p þ π0 ðor n þ πþÞ, where n is the total number of the produced π’s. In 2016, the ANITA experiment has reported one unusual steeply upward-pointing cosmic ray event 3985267 with a shower energy around 0.6 EeV during the ANITA-I flight [5] This shower event could be generated by the decay of a τ lepton, which is emerging from the surface of the ice with the zenith angle around. When the sterile flux goes through the Earth, they will effectively experience a suppressed cross section due to the small active-sterile mixing In such a way, the neutrinos can make their way to the thin interaction region below the ANITA detector, being converted to the τ lepton by the CC interaction with the ice, water, or rock.

PROPAGATION OF STERILE NEUTRINOS

ANITA EVENTS ESTIMATION

Findings

CONCLUSION