universe
Communication Latest Results from the T2K Neutrino Experiment†
Dean Karlen and on behalf of the T2K Collaboration
Department of Physics and Astronomy, Univeristy of Victoria and TRIUMF, Victoria, BC V8P 5C2, Canada; [email protected] † This paper is based on the talk at the 7th International Conference on New Frontiers in Physics (ICNFP 2018), Crete, Greece, 4–12 July 2018.
Received: 16 November 2018; Accepted: 2 January 2019; Published: 9 January 2019
Abstract: The T2K long baseline neutrino oscillation experiment measures muon neutrino disappearance and electron neutrino appearance in accelerator-produced neutrino and anti-neutrino beams. This presentation reports on the analysis of our data from an exposure of 2.6 × 1021 protons on target. Results for oscillation parameters, including the CP violation parameter and neutrino mass ordering, are shown.
Keywords: neutrino; neutrino oscillation; neutrino properties; CP violation
1. Introduction to Lepton Mixing Super-Kamiokande [1] and Sudbury Neutrino Observatory [2] measurements of neutrinos produced naturally in the sun and from interactions of cosmic rays with the atmosphere established that leptons mix and that neutrinos have mass. These achievements led to the 2015 Novel Prize in Physics being awarded to Takaaki Kajita and Arthur B. McDonald. Lepton mixing is described by the Pontecorvo–Maki–Nakagawa–Sakata (PMNS) matrix, U, such that each neutrino flavour state, |ναi, is a linear combination of mass states, |νii, with mass mi,
∗ |ναi = ∑ Uαi|νii . (1) i
Due to this mixing, a neutrino produced with a definite flavour α can be detected as another flavour β. In the absence of matter, the amplitude for flavour change of a neutrino with energy E a distance L from its production point is given by [3]
2 ∗ −imi L/(2E) Amp να → νβ = ∑ Uαi e Uβi . (2) i
The corresponding probability for neutrino flavour change is