Predictions for the isospin-violating decays of $B_{c}(1P)^{+}\to B_{c}^{(*)+}\pi^{0}$

Abstract

In this work we study the isospin-violating decays of $B_{c}(1P)^{+}\to B_{c}^{(*)+}\pi^{0}$, which may provide additional information for the determination of the properties of the first orbital excitation states of $B_{c}(1P)^{+}$. By assuming a dual relation between the U(1) anomaly soft-gluon coupling for $B_{c}(1P)^{+}\to B_{c}^{(*)+}\pi^{0}$ and the intermediate meson loop transitions, we can quantify the isospin-violating decay effects for these four $P$-wave states. We find that the partial decay width of $B_{c0}^{*+}\to B_{c}^{+}\pi^{0}$ is about three orders of magnitude larger than that for $B_{c2}^{*+}\to B_{c}^{+}\pi^{0}$. It implies that $B_{c0}^{*+}$ can be established in the $B_{c}^{+}\pi^{0}$ decay channel as a single state. Meanwhile, the two axial-vector states $B_{c1}^{+}/B_{c1}'^{+}$ can be possibly identified in $B_{c1}^{+}/B_{c1}'^{+}\to B_{c}^{*+}\pi^{0}$ with comparable strengths. Although these isospin-violating decays turn out to be small, the theoretical predictions should be useful for guiding future experimental efforts.