First measurement of the strange axial coupling constant using neutral-current quasielastic interactions of atmospheric neutrinos at KamLAND

Abstract

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. 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 with high efficiency. KamLAND data, including the information on neutron multiplicity associated with the NCQE interactions, makes it possible to measure $g_A^s$ 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 establish a simulation of particle emission via nuclear deexcitation of ${}^{12}$C, a process not considered in existing neutrino Monte Carlo event generators. Energy spectrum fitting for each neutron multiplicity gives $g_A^s=-0.14_{-0.26}^{+0.25}$, which is the most stringent limit obtained using NCQE interactions without $M_A$ constraints. The two-body current contribution considered in this analysis relies on a theoretically effective model and electron scattering experiments and requires future verification by direct measurements and future model improvement.

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Cited by in corpus (6)

• Nuclear deexcitation simulator for neutrino interactions and nucleon decays of ${}^{12}\text{C}$ and ${}^{16}\text{O}$ based on TALYS
• Implementation and investigation of electron-nucleus scattering in the \textsc{NEUT} neutrino event generator
• Measurement of neutron production in atmospheric neutrino interactions at Super-Kamiokande
• Neutrino nucleus Quasi-Elastic and resonant Neutral Current scatterings with Non-Standard Interactions
• Neutral-current background induced by atmospheric neutrinos at large liquid-scintillator detectors: III. Comprehensive prediction for low energy neutrinos
• Benchmarks and applications of the nuclear deexcitation event generator NucDeEx