Deconvolution in Measurements of Muon Neutrino Energy Spectra with IceCube

Tim Ruhe,C Spiering

doi:10.1051/epjconf/201920705006

Abstract

As the energy of an incident neutrino cannot be accessed experimentally, muon neutrino energy spectra have to be inferred from energy-dependent observables, using deconvolution algorithms. This paper discusses the challenges associated with the application of deconvolution algorithms and presents two examples of spectral measurements obtained using the IceCube neutrino telescope in the 59- and 79-string configuration.

Highlights

Neutrino Energy Spectra and Challenges in DeconvolutionIn IceCube muon-neutrinos are not detected directly, but via secondary muons produced in charged-current (CC) interactions of the incident neutrino with nuclei in the ice or the bedrock
As the energy of an incident neutrino cannot be accessed experimentally, muon neutrino energy spectra have to be inferred from energy-dependent observables, using deconvolution algorithms
This is due to the steeply falling spectrum of conventional atmospheric neutrinos, which implies that even a small number of atmospheric muons, passing the event selection may mimic the contribution of an additional component to the spectrum at high energies

Summary

Neutrino Energy Spectra and Challenges in Deconvolution

In IceCube muon-neutrinos are not detected directly, but via secondary muons produced in charged-current (CC) interactions of the incident neutrino with nuclei in the ice or the bedrock. The neutrino energy spectrum dN/dEν is experimentally inaccessible and has to be inferred using the energy spectrum of secondary muons dNμ/dEμ. The first component are so-called conventional atmospheric neutrinos, originating from the decay of pions and kaons produced in cosmic ray airshowers. Due to the relatively long lifetime of pions and kaons τ ≈ 10−8 s [2], the spectrum of conventional atmospheric neutrinos is approximately one power steeper than the cosmic ray energy spectrum (dNconv/dEν ≈ E−3.7). The second component are prompt atmospheric neutrinos, from the decay of charmed particles Due to their short lifetime τ ≈ 10−12 s [2], prompt atmospheric neutrinos inherit the cosmic ray spectrum more directly and the resulting flux is dNprompt/dEν ≈ E−2.7. Atmospheric muons are a significant background in neutrino searches and need to be efficiently rejected

Deconvolution Algorithms

Selected Deconvolution Results

Discussion and Outlook