Measurement of neutrino and antineutrino oscillations by the T2K experiment including a new additional sample ofνeinteractions at the far detector

Abstract

The T2K experiment reports an updated analysis of neutrino and antineutrino oscillations in appearance and disappearance channels. A sample of electron neutrino candidates at Super-Kamiokande in which a pion decay has been tagged is added to the four single-ring samples used in previous T2K oscillation analyses. Through combined analyses of these five samples, simultaneous measurements of four oscillation parameters, jΔm 2 32 j, sin 2 θ 23 , sin 2 θ 13 , and δ CP and of the mass ordering are made. A set of studies of simulated data indicates that the sensitivity to the oscillation parameters is not limited by neutrino interaction model uncertainty. Multiple oscillation analyses are performed, and frequentist and Bayesian intervals are presented for combinations of the oscillation parameters with and without the inclusion of reactor constraints on sin 2 θ 13. When combined with reactor measurements, the hypothesis of CP conservation (δ CP ¼ 0 or π) is excluded at 90% confidence level. The 90% confidence region for δ CP is ½−2.95; −0.44 (½−1.47; −1.27) for normal (inverted) ordering. The central values and 68% confidence intervals for the other oscillation parameters for normal (inverted) ordering are Δm 2 32 ¼ 2.54 AE 0.08ð2.51 AE 0.08Þ × 10 −3 eV 2 =c 4 and sin 2 θ 23 ¼ 0.55 þ0.05 −0.09 (0.55 þ0.05 −0.08), compatible with maximal mixing. In the Bayesian analysis, the data weakly prefer normal ordering (Bayes factor 3.7) and the upper octant for sin 2 θ 23 (Bayes factor 2.4).

Results and Prospects from NOvA

“…Figure 2 (right) depicts the NOvA 90% C.L. contour in comparison to previous results from MINOS [9] and T2K [10]. For a full discussion of the details of the muon neutrino disappearance analysis refer to the publication in Ref.…”

“…Right: NOvA's best-fit (black dots) points and allowed 90% C.L. regions compared to previous results from MINOS [9] and T2K [10] (dashed curves).…”

Neutrino versus antineutrino oscillation parameters at DUNE and Hyper-Kamiokande experiments

“…The results recently published by T2K are ∆m 2 32 = (2.54 ± 0.08) × 10 −3 eV 2 and sin 2 θ 23 = 0.55 +0.05 −0.09 [47], both for a normal mass-hierarchy. Results for the inverted hierarchy are similar (up to ∆m 2 32 approximately changing sign).…”

“…Neutrino oscillation parameters are mostly constrained by solar neutrino experiments [40][41][42][43][44][45], the SuperKamiokande atmospheric neutrino data [37], and accelerator data from MINOS [46], T2K [47], and the NuMI Off-Axis ν e Appearance Experiment (NOνA) [48]. These imply the existence of two hierarchical mass-squared differences ∆m 2 21 and ∆m 2 32 and three nonzero mixing angles θ 13 , θ 12 , θ 23 .…”

“…MINOS, T2K and NOνA-Accelerator experiments sensitive to ν µ -disappearance for L/E values around 10 3 eV −2 provide the most stringent bounds on ∆m 2 32 and sin 2 θ 23 [39,[46][47][48]. The results recently published by T2K are ∆m 2 32 = (2.54 ± 0.08) × 10 −3 eV 2 and sin 2 θ 23 = 0.55 +0.05 −0.09 [47], both for a normal mass-hierarchy.…”