Jianming Bian’s group plays key role in new NOvA results shedding light on neutrino mass

The ordering of neutrino mass eigenstates, and the neutrino CP phase angle, are the two fundamental particle physics problems that can be solved by long-baseline neutrino experiments such as NOvA (NuMI Off-axis Electron Neutrino Appearance Experiment) and DUNE (Deep Underground Neutrino Experiment). Neutrino mass ordering is a key to resolving absolute neutrino masses and to establishing grand unified theories. The CP phase angle, which describes the difference between neutrino and antineutrino oscillations, holds implications for matter-antimatter asymmetry in our universe. The latest results from NOvA prefer a normal neutrino mass ordering, observe significant electron antineutrino appearance, and exclude most values near the CP phase angle equal to 90 degrees for the inverted mass ordering. These results have been published in last week's issue of Physical Review Letters (https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.123.151803, https://arxiv.org/abs/1906.04907).

The international NOvA collaboration is made up of more than 240 scientists and engineers from 51 institutions in seven countries. The UCI long-baseline neutrino group, led by Prof. Jianming Bian, played a key role in this latest NOvA publication. Prof. Bian leads the NOvA reconstruction and deep-learning inter-institute group, which applies traditional and deep-learning methods to reconstruct neutrino events recorded by NOvA detectors. The UCI group played a leading role in the electron (anti)neutrino appearance analyses that produced these new results. UCI Ph.D. student Nitish Nayak served as one of the four editors of this paper, along with former and current NOvA spokespersons. Collaborating with UCI Computer Science professor Pierre Baldi, Bian’s group has been developing deep-learning methods and software used by the NOvA collaboration. The next NOvA collaboration meeting will be held February 13-16, 2020, at UCI.

Bian’s group is also productively involved in DUNE, the next-generation flagship neutrino experiment in the U.S., which is designed to decisively determine neutrino CP phase angle and mass ordering.