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

Abe, S.; Asami, S.; Axani, S. N.; Berger, B. E.; Decowski, M. P.; Dell'Oro, S.; Detwiler, J. A.; Efremenko, Y.; Eizuka, M.; Enomoto, S.; Fu, Z.; Fujikawa, B. K.; Fushimi, K.; Futagi, S.; Gando, A.; Gando, Y.; Gima, T.; Goto, A.; Grant, C.; Hachiya, T.; Hata, K.; Ichikawa, A. K.; Ichimura, K.; Ieki, S.; Ikeda, H.; Inoue, K.; Ishidoshiro, K.; Kamei, Y.; KamLAND Collaboration; Karwowski, H. J.; Kawada, N.; Kishimoto, Y.; Koga, M.; Kotera, K.; Kurasawa, M.; Learned, J. G.; Li, A.; Maricic, J.; Markoff, D. M.; Mitsui, T.; Miyake, H.; Nakahata, T.; Nakamura, K.; Nakamura, R.; O'Donnell, T.; Obara, S.; Ozaki, H.; Sakai, T.; Shimizu, I.; Shirai, J.; Shiraishi, K.; Smolsky, J.; Song, H.; Suzuki, A.; Suzuki, Y.; Takeuchi, A.; Tamae, K.; Tornow, W.; Umehara, S.; Urano, Y.; Watanabe, H.; Winslow, L. A.; Yoshida, S.; Yoshida, Y.

First measurement of the strange axial coupling constant using neutral-current quasi-elastic 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 quasi-elastic (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 de-excitation of