Threshold effect and \pi^\pm \psi(2S) peak

Abstract

A resonance-like structure in the $\pi^\pm \psi(2S)$ mass spectrum arising in $B \to K \pi^\pm \psi(2S)$ has recently been reported. It is noted that the mass of this structure, $4433 \pm 4 \pm 1$ MeV, is not far from the threshold for production of $D^* \bar{D}_1(2420)$. A proposed mechanism for production of this state is suggested, and tests are suggested.