Complementarity between atmospheric and super-beam neutrinos at ESSnuSB

TL;DR

This paper investigates how atmospheric neutrino data can enhance the precision of leptonic CP phase measurements at ESSnuSB, demonstrating improved resolution and degeneracy resolution through combined analysis.

Contribution

It introduces a detailed simulation of atmospheric neutrino data for ESSnuSB and quantifies its impact on CP phase measurement precision and degeneracy resolution.

Findings

Atmospheric neutrinos improve δ_CP resolution from 7.5° to 7.1° at 1σ CL.

Combined data resolves neutrino mass ordering degeneracies.

Synergies between super-beam and atmospheric neutrinos enhance measurement accuracy.

Abstract

The ESSnuSB experiment aims to measure the leptonic CP phase $\delta_{CP}$ with an unprecedented resolution by probing neutrino oscillations at the second oscillation maximum. In the present work, the complementarity between the long-baseline neutrino program and atmospheric neutrinos is investigated for ESSnuSB. By simulating atmospheric neutrino events equivalent of 5.4 Mt$\cdot$year exposure, the resolution for $\delta_{\rm CP}^{}$ is found to improve from $7.5^\circ$ ($6.7^\circ$) to $7.1^\circ$ ($6.5^\circ$) at $1\sigma$~CL for $\delta_{\rm CP}^{} = -90^\circ$ ($+90^\circ$) with respect to super-beam neutrinos, resolving also the degeneracies arising from neutrino mass ordering. These findings highlight the synergies that exist between super-beam neutrinos and atmospheric neutrinos in ESSnuSB.