Progress on the neutrino mixing angle, theta_13

TL;DR

Recent advances in reactor and accelerator experiments have significantly improved measurements of the neutrino mixing angle theta_13, crucial for understanding CP violation and neutrino mass hierarchy.

Contribution

This paper summarizes the current progress and experimental status of measuring theta_13 during a pivotal period in neutrino research.

Findings

Significant experimental progress in measuring theta_13

Indications that theta_13 differs from zero

Future experiments will test the PMNS framework

Abstract

Until recently, measurements of theta_13, which describes the nu_e component in the nu_3 mass eigenstate, gave only upper limits, leaving open the possibility that it is zero and eliminating a source of CP violation in the neutrino sector. This year has seen significant advances in measuring theta_13 as precision reactor experiments move from construction phase to physics operation and accelerator experiments give first indications that theta_13 differs from zero. In the years to come, the results from these and other experiments will stringently test the PMNS framework for neutrino oscillation and will start to give information about neutrino CP violation and the neutrino mass hierarchy. This paper summarizes the situation for measuring theta_13 at this pivotal time in neutrino research.