Structure of $X_b$ from line shape analysis

Abstract

We study the production line shape of $B^\ast\bar B$ near threshold, where the $B^\ast \bar B$ pair comes from the resonance $X_b$. Our study shows that the line shape depends sensitively on the binding energy and the probability of finding an elementary state in the physical bound state. Both of the two parameters are crucial to identify the structure of $X_b$. Therefore, the line shape measurement can shed light on the structure of $X_b$.