Rare radiative decays of the $B_c$ meson

In this paper, we study the rare radiative processes $B_c\to D_{sJ} ^{(*)}\gamma$ within the Standard Model, where $D_{sJ}^{(*)}$ stands for the meson $D_s^*$,~$D_{s1}(2460,2536)$ or ~$D_{s2}^*(2573)$. During the investigations, we consider the contributions from the penguin, annihilation, color-suppressed and color-favored cascade diagrams. Our results show that: 1) the penguin and annihilation contributions are dominant in the branching fractions; 2) for the processes $B_c\to D_s^{*}\gamma$ and $B_c\to D_{s1}(2460,2536)\gamma$, the effects from the color-suppressed and color-favored cascade diagrams are un-negligible.