PHYSICAL REVIEW D 107, 016013 (2023)

ISSN: 2470-0029, SCIE

Stringent constraint on CPT violation with the synergy of T2K-II, NOνA extension, and JUNO

T. V. Ngoc, S. Cao, N. T. Hong Van, and P. T. Quyen

Neutrino oscillation experiments have measured precisely at few percent levels the mass-squared differences (Δm2 21, Δm2 31) of three neutrino mass eigenstates, and the three leptonic mixing angles (θ12, θ13, θ23) by utilizing both neutrino and antineutrino oscillations. The possible CPT violation may manifest itself in the difference of neutrino and antineutrino oscillation parameters, making these experiments promising tools for testing CPT invariance at unprecedented precision. We investigate empirically the sensitivity of the CPT test via the difference in mass-squared splittings (Δm2 31 − Δ ¯m2 31) and in leptonic mixing angles (sin2 θ23 − sin2 ¯θ23) with the synergy of T2K-II, NOνA extension, and JUNO experiments. If the CPT symmetry is found to be conserved, the joint analysis of the three experiments will be able to establish limits of jΔm2 31 − Δ ¯m2 31j < 5.3 × 10−3 eV2 and j sin2 θ23 − sin2 ¯θ23j < 0.10 at 3σ confidence level (CL) on the possible CPT violation, extending substantially the current bound of these parameters. We find that with (Δm2 31 − Δ ¯m2 31), the dependence of the statistical significance on the relevant parameters to exclude the CPT conservation is marginal, and that, if the difference in the best-fit values of Δm2 31 and Δ ¯m2 31 measured by MINOSðþÞ and NOνA persists as the true, the combined analysis will rule out the CPT conservation at 4σ CL. With the (sin2 θ23 − sin2 ¯θ23), the statistical significance to exclude CPT invariance depends strongly on the true value of θ23ð¯θ23Þ mixing angle. In the case of maximal mixing of θ23, as indicated by the current T2K and NOνA measurements, the CPT conservation will be excluded at 3σ CL or higher if the difference in the best-fit values of θ23 and ¯θ23 remains as the true.

DOI: DOI: 10.1103/PhysRevD.107.016013