First Observation and Dynamical Study of the $D^+_s\to f_{0}(980) \mu^+\nu_\mu$ Decay
Using 7.33 fb$^{-1}$ of $e^+e^-$ annihilation data recorded with the BESIII detector at center-of-mass energies from 4.128 to 4.226 GeV, we report the first observation and dynamical study of the semileptonic decay $D^+_s\to f_{0}(980) \mu^+\nu_\mu$. The absolute branching fraction of $D^+_s\to f_{0}(980) \mu^+\nu_\mu$...