Edepillim: a new muon energy reconstruction for the IceCube Neutrino Observatory

Abstract

Neutrinos are an ideal tracer particle for high energy astrophysics as they are not deflected by magnetic fields. As such they can be detected at Earth with their directional information intact, however because of the low interaction probability they are difficult to detect. The IceCube Neutrino Observatory operates by observing Cherenkov radiation emitted from charged secondary interaction particles of neutrinos such as muons. As a muon travels though the detector it experiences energy loss due to radiative processes which will be represented by an energy loss pattern with stochastic losses, the probability of these losses is dependent on the initial energy of the muon. The muon energy reconstruction method Edepillim described in this work takes into account the entire pattern of energy loss along the muon track and uses probability distribution functions describing muon energy losses to perform a maximum likelihood reconstruction for the initial muon energy. This work demonstrates the good reconstruction resolution of this method on idealised simulation by comparison to other energy reconstruction methods. In addition the method was implemented on simulated muon events where the pattern of energy losses have been reconstructed, and the limitations and improvements needed to be made to the energy loss pattern for optimal resolution are discussed. Finally in this work the energy reconstruction method was tested on a sample of up-going neutrino-induced muon events, by performing a diffuse fit to atmospheric and astrophysical ux predictions. This fit demonstrates the improvement that this energy resolution has on the confidence interval on the value of the fitted astrophysical flux results. Also discussed is a specific example of reconstructing IceCube's highest energy muon neutrino event using Edepillim.