First Antineutrino Oscillation Results from T2K

Abstract

As limits improve on the neutrino mixing angles and mass-squared differences, the focus of T2K has shifted towards studying antineutrino oscillation. This will give an insight into CP violation (if P($\bar{\nu}_{\mu} \rightarrow \bar{\nu}_{e}) \neq \mbox{P}(\nu_{\mu} \rightarrow \nu_e)$) and CPT violation (if P($\bar{\nu}_{\mu} \rightarrow \bar{\nu}_{\mu}) \neq \mbox{P}(\nu_{\mu} \rightarrow \nu_{\mu})$) in the lepton sector. This poster summarises the most recent T2K antineutrino oscillation results, from data collected using a $\bar{\nu}_{\mu}$-enhanced neutrino beam corresponding to $4.01 \times 10^{20}$ protons on target (roughly $1/3$ of the total protons on target collected by T2K). We present world-leading measurements of $\Delta \bar{m}^2_{32}$ and $\sin^2\bar{\theta}_{23}$ and the first analysis of $\bar{\nu}_e$ appearance from T2K. Both results use a Bayesian oscillation analysis based on a Markov Chain Monte Carlo method in which data from the near detector and far detector are fit simultaneously.