Programme

P.37 -- Poster, VCTP-45

Date: Tuesday, 13 October 2020

Time: 08:30 - 10:00

Resolving the octant of leptonic mixing angle $\theta_{23}$ with Hyper-Kamiokande experiment.

Phan To Quyen (1), Cao Van Son (2), Nguyen Thi Hong Van (3), Ankur Nath (4), Tran Van Ngoc (1)

(1) Institute For Interdiscliplinary Research in Science and Education (IFIRSE), Quy Nhon, Vietnam; (2) High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki, Japan; (3) Institute of Physics, Vietnam Academy of Science and Technology (VAST), Hanoi, Vietnam; (4) Department of Physics, Tezpur University, Tezpur, Assam, India

Super-Kamiokande discovered neutrino oscillation in 1998 and Hyper-Kamiokande, which is effectively eight time larger than its predecessor and approved for reconstruction from 2020, will be a discovery machine for proton decays, CP violation in neutrino oscillation and detection of astrophysical neutrinos. This study explores the physics potential of Hyper-Kamiokande in measuring the $\theta_{23}$ mixing parameter, which presents a factional contribution of $\nu_{\mu}$ and $\nu_{\tau}$ in the neutrino mass eigenstate $\nu_3$. If its value is exactly equal to $\pi/4$ , it indicates some unknown symmetry between muon and tau. We use two types of simulated samples produced from the accelerator-based muon neutrino source: (i) survived muon neutrinos, and (ii) appeared electron neutrinos. The former can determine precisely $\sin^{2}2\theta_{23}$ but can not know if $\theta_{23}$ is in lower octant ($\theta_{23}<\pi/4$) or in higher octant ($\theta_{23}>\pi/4$). The later depends on $\sin^{2}\theta_{23}$, but also on $\sin^2_{13}$ and $\delta_{CP}$, which makes measurement statistically limited and parameter-degeneracy dependent. It will be shown that the $\theta_{23}$ octant resolving can be improved significantly with constraints established by reactor experiments and systematic improvement of appearance samples. It will be also shown how the octant determination can help the measurement of CP violation in the lepton sector.

Presenter: Phan To Quyen

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