Stringent constraints on nonstandard neutrino interactions using high-purity ${\nu }_{\mu }$ CC events in IceCube DeepCore

Abstract

The neutral-current (NC) nonstandard interactions (NSIs) of neutrinos with fermions can modify the flavor oscillations of atmospheric neutrinos as they propagate through the Earth. We present constraints on the NC-NSI parameters ${\epsilon }_{\mu \tau }$ and ${\epsilon }_{\tau \tau }-{\epsilon }_{\mu \mu }$ (one at a time) using a high-purity sample of ${\nu }_{\mu }$ charged-current atmospheric neutrino events collected by IceCube DeepCore over 7.5 years of livetime. These two parameters significantly affect the ${\nu }_{\mu }$ disappearance channel for which this golden event sample is optimized by IceCube Collaboration. The best fit to this dataset is consistent with no NSI hypothesis, and we place the stringent constraints $-0.0094<{\epsilon }_{\mu \tau }<0.0079$ and $-0.031<{\epsilon }_{\tau \tau }-{\epsilon }_{\mu \mu }<0.029$ at the 90% confidence level, assuming normal mass ordering.

12 pages, 12 figures, 1 table, and 5 appendices. New appendices added. The manuscript now matches the published PRD version. We congratulate Professor Francis Halzen and the entire IceCube Collaboration on being awarded the 2026 Nobel Prize in Physics. This work would not have been possible without Professor Halzen's constant support. This publication is our fitting tribute to Professor Halzen