Bounds on Neutrino-Scalar Yukawa Coupling

Abstract

General neutrino-scalar couplings appear in many extensions of Standard Model. We can probe these neutrino-scalar couplings by leptonic decay of mesons and from heavy neutrino search. Our analysis improves the present limits to $|g_e{|}^2<1.9\times 10^{-6}$ and $|g_{\mu }{|}^2<1.9\times 10^{-7}$ at 90\% C.L. for massless scalars. For massive scalars we found for the first time the constraints for $g_{\alpha }^2$ couplings to be $10^{-6}-10^{-1}$ respectively for scalar masses between below 1 MeV and for 300 MeV.

Comments: 8 pages, 7 figures