Session K02: Understanding the Neutrino Sector

Neutrino Mass - Origins

I provide an overview of the different ideas for the physics behind nonzero neutrino masses, highlighting what these imply for our understanding of fundamental physics, how they may be tested in the future, and how they related to other outstanding questions in particle physics.   

Neutrino-Mass Limits Through Beta Decay

Twenty years after the discovery of neutrino oscillations established non-zero neutrino mass, the absolute neutrino-mass scale remains unknown. In this talk, I will review current laboratory-based efforts to measure the neutrino mass directly, with minimal model dependence, through the endpoint kinematics of beta decays in two isotopes: tritium and holmium-163. The KATRIN collaboration has commissioned its beamline with calibration sources, and is moving toward tritium commissioning; the Project 8 collaboration is working to demonstrate its measurement principle with tritium gas for the first time. Meanwhile, the ECHo, HOLMES, and NuMECS collaborations are finalizing detector technologies, and scaling up to pursue competitive holmium-based measurements. I will discuss some of the technical and scientific challenges faced by each approach, and share recent achievements on the path to a better understanding of neutrino mass.   

Three-flavor Neutrino Mixing

Understanding neutrino properties through measurements of neutrino flavor mixing has motivated the development of a rich worldwide experimental program. Detectors employing a wide variety of technologies measure neutrinos originating in the Earth's atmosphere, in the Sun, in nuclear reactors, or created with particle accelerators. Precision measurements of neutrino oscillations play a crucial role in probing CP violation in the leptonic sector, which could have fundamental implications in generating a baryon asymmetry in the early universe, in determining the neutrino mass ordering, and in potentially unveiling new symmetries governing the neutrino mixing matrix. In this talk, I will review the phenomenology of three-neutrino mixing, summarize the current experimental results, and discuss global plans to answer some of the most pressing questions in neutrino physics with present and future neutrino oscillation experiments.