First measurement of the strange axial coupling constant using neutral-current quasielastic interactions of atmospheric neutrinos at KamLAND
by
Seisho Abe
(Research Center for Neutrino Science, Tohoku University, Japan)
→
US/Central
Description
This seminar is based on a paper on arXiv (https://arxiv.org/abs/2211.13911). We report a measurement of the strange axial coupling constant g_A^s using atmospheric neutrino data at KamLAND. This constant is a component of the axial form factor of the neutral-current quasielastic (NCQE) interaction and corresponds to the strange quark-antiquark contribution to the nucleon spin. The value of g_A^s significantly changes the ratio of proton and neutron NCQE cross sections. KamLAND is suitable for measuring NCQE interactions as it can detect nucleon recoils with low-energy thresholds and measure neutron multiplicity. KamLAND data, including information on neutron multiplicity associated with the NCQE interactions, make it possible to measure the g_A^s t with a suppressed dependence on the axial mass M_A, which has not yet been determined. For a comprehensive prediction of the neutron emission associated with neutrino interactions, we established a simulation of particle emission via nuclear deexcitation of carbon, a process not considered in existing neutrino Monte Carlo event generators. From energy spectrum fitting, we obtain g_A^s = -0.14^{+0.25}_{-0.26}, which is the most stringent limit obtained using NCQE interactions without M_A constraints.