Optimised sensitivity to leptonic CP violation from spectral information: the LBNO case at 2300 km baseline

TL;DR

This paper presents an optimized neutrino flux configuration for the LBNO experiment at 2300 km, enhancing sensitivity to leptonic CP violation by utilizing spectral information from both oscillation maxima and reducing systematic error sensitivity.

Contribution

The study introduces a numerical optimization of the neutrino flux spectra for LBNO, improving CP violation sensitivity by leveraging spectral data from multiple oscillation maxima.

Findings

Optimized flux enhances CP sensitivity compared to non-optimized configurations.

Both oscillation maxima are crucial for maximizing CP violation detection.

The optimized setup is less sensitive to systematic uncertainties.

Abstract

One of the main goals of the Long Baseline Neutrino Observatory (LBNO) is to study the $L/E$ behaviour (spectral information) of the electron neutrino and antineutrino appearance probabilities, in order to determine the unknown CP-violation phase $\delta_{CP}$ and discover CP-violation in the leptonic sector. The result is based on the measurement of the appearance probabilities in a broad range of energies, covering t he 1st and 2nd oscillation maxima, at a very long baseline of 2300 km. The sensitivity of the experiment can be maximised by optimising the energy spectra of the neutrino and anti-neutrino fluxes. Such an optimisation requires exploring an extended range of parameters describing in details the geometries and properties of the primary protons, hadron target and focusing elements in the neutrino beam line. In this paper we present a numerical solution that leads to an optimised energy spectra and study its impact on the sensitivity of LBNO to discover leptonic CP violation. In the optimised flux both 1st and 2nd oscillation maxima play an important role in the CP sensitivity. The studies also show that this configuration is less sensitive to systematic errors (e.g. on the total event rates) than an experiment which mainly relies on the neutrino-antineutrino asymmetry at the 1st maximum to determine the existence of CP-violation.