The mass-hierarchy and CP-violation discovery reach of the LBNO long-baseline neutrino experiment

TL;DR

The LBNO experiment aims to determine the neutrino mass hierarchy with high confidence and has significant potential to discover CP-violation in neutrino oscillations within a few years of operation, using a long-baseline setup and conventional neutrino beams.

Contribution

This paper reevaluates the LBNO experiment's potential for mass hierarchy determination and CP-violation discovery, emphasizing the importance of statistical treatment and systematic uncertainties.

Findings

LBNO can determine the mass hierarchy with >5σ confidence over all parameter space.

The experiment has ~100% probability to identify the mass hierarchy within 4-5 years.

LBNO can provide evidence for CP-violation at 3σ confidence level using current knowledge.

Abstract

The next generation neutrino observatory proposed by the LBNO collaboration will address fundamental questions in particle and astroparticle physics. The experiment consists of a far detector, in its first stage a 20 kt LAr double phase TPC and a magnetised iron calorimeter, situated at 2300 km from CERN and a near detector based on a high-pressure argon gas TPC. The long baseline provides a unique opportunity to study neutrino flavour oscillations over their 1st and 2nd oscillation maxima exploring the $L/E$ behaviour, and distinguishing effects arising from $\delta_{CP}$ and matter. In this paper we have reevaluated the physics potential of this setup for determining the mass hierarchy (MH) and discovering CP-violation (CPV), using a conventional neutrino beam from the CERN SPS with a power of 750 kW. We use conservative assumptions on the knowledge of oscillation parameter priors and systematic uncertainties. The impact of each systematic error and the precision of oscillation prior is shown. We demonstrate that the first stage of LBNO can determine unambiguously the MH to $>5\sigma$C.L. over the whole phase space. We show that the statistical treatment of the experiment is of very high importance, resulting in the conclusion that LBNO has $\sim$ 100% probability to determine the MH in at most 4-5 years of running. Since the knowledge of MH is indispensable to extract $\delta_{CP}$ from the data, the first LBNO phase can convincingly give evidence for CPV on the $3\sigma$C.L. using today's knowledge on oscillation parameters and realistic assumptions on the systematic uncertainties.