Measuring the atmospheric muon neutrino and anti-neutrino flux ratio with the ATLAS detector at LHC

TL;DR

This study explores the potential of the ATLAS detector at the LHC to measure the atmospheric muon neutrino to anti-neutrino flux ratio as a function of energy, addressing uncertainties in flux models at higher energies.

Contribution

It demonstrates a method to measure the atmospheric muon neutrino/anti-neutrino flux ratio using ATLAS data, including event selection and background elimination techniques.

Findings

Feasible measurement of flux ratio up to 100 GeV energy.

Estimated event counts: 63 mu- and 32 mu+ contained vertex events.

Estimated event counts: 630 mu- and 307 mu+ external upward events.

Abstract

There is a significant uncertainty in the prediction of atmospheric muon neutrino and anti-neutrino flux ratio using different flux models, especially at higher energies. We study the prospects of experimentally measuring this flux ratio as a function of energy with the ATLAS detector at the LHC. To this end, we compute the contained-vertex and external upward going charged current event rates induced by atmospheric muon (anti-)neutrinos through deep inelastic scattering at the 4 kiloton hadron calorimeter (HCAL) component of ATLAS. We illustrate the event selection criteria necessary to eliminate the cosmic ray muon background for the above event classes. While the contained vertex events have a striking topology with a muon being created inside the HCAL and then travelling to the muon chamber possibly through the tracker, for muons with energy larger than 3 GeV, a much higher statistics is obtained for the external upward going events created in the rock column below the detector. Our estimates show that the energy dependence of the ratio of negative and positively charged muons induced by atmospheric muon neutrino and anti-neutrino fluxes can be measured by ATLAS upto a muon energy of 100 GeV, with 1000-live days of neutrino physics exposure over a period of several years, considering only the period with the LHC beams not in circulation, but the detector and magnetic fields of ATLAS in operation. With this exposure, we obtain $63~\mu^-$ and $32~\mu^+$ contained vertex events, and $630~\mu^-$ and $307~\mu^+$ external upward-going events, after imposing the necessary selection criteria.