The production and strong decays of D _q(2S) and B _q(2S)

We study the production of first radial excited states D _q(2S) (q = u, d, s) and B _q(2S) in exclusive semi-leptonic (q = u, d, s, c) decays by the improved Bethe-Salpeter method. These 2S states can be detected through their strong decays to ground mesons, where the strong decays are calculated by the low-energy approximation as well as the impulse approximation. Some channels have ratios of order 10 ⁴: , . These channels could be measured by the current B-factories. For D _s(2S), we also obtain a relative large ratio: . Although there are discrepancies in the full decay width between the theoretical predictions of D ⁰(2S) and the experimental results of D(2550) ⁰, the new detected state D(2550) ⁰ is very likely the D ⁰(2S) state.