Form factors for semileptonic $B_{c}$ decays into $\eta^{(')}$ and Glueball
We calculated the form factors of $B_{c}$ transitions into $\eta^{(')}$ meson and pseudoscalar Glueball, where the $B_{c}$ meson is a bound state of two different heavy flavors and is treated as a nonrelativistic state, while the mesons $\eta^{(')}$ and Glueball are treated as light-cone objects since their masses are smaller enough compared to the transition momentum scale. The mechanism of two gluon scattering into $\eta^{(')}$ dominated the form factors of $B_{c}$ decays into $\eta^{(')}$. We considered the $\eta-\eta'-$Glueball mixing effect, and then obtained their influences on the form factors. The form factors of $B_{c}$ transitions into $\eta^{(')}$ and pseudoscalar Glueball in the maximum momentum recoil point were obtained as follows: $f^\eta_{0,+}(q^2=0)=1.38^{+0.00}_{-0.02}\times 10^{-3}$,$f^{\eta'}_{0,+}(q^2=0)=0.89^{+0.11}_{-0.10}\times 10^{-2}$ and $f^{G}_{0,+}(q^2=0)=0.44^{+0.13}_{-0.05}\times 10^{-2}$. Also phenomenological discussions for semileptonic $B_{c}\to\eta^{(')}+\ell+\bar{\nu}_\ell$, $B_{c}\to G(0^{-+})+\ell+\bar{\nu}_\ell$ and $D_{s}\to \eta+\ell+\bar{\nu}_\ell$ decays are given.