Speaker
Description
It is demonstrated that,if the lightest positive parity charm mesons are assumed to owe their existence to non-perturbative Goldstoneboson$D/D^∗$ scattering, various puzzles in the charm meson spectrum get resolved. Most importantly the ordering of the lightest strange and non-strange scalars becomes natural. It is demonstrated that the amplitudes for Goldstone boson-$D/D^∗$ scattering are fully consistent with the high quality data on decays $B^-\to D^+\pi^-\pi^-$, $B_s^0\to \bar{D}^0K^-\pi^+$, $B^0\to\bar{D}^0\pi^-\pi^+$, $B^-\to D^+\pi^-K^-$ and $B^0\to\bar{D}^0\pi^-K^+$, provided by LHCb. The results provide a strong support of the scenario that the broad scalar charmed meson $D^\ast_0(2400)$ should be replaced by two states, the lower one of which has a mass of around 2.1 GeV, much smaller than that extracted from experimental data using a Breit--Wigner parameterization. It implies that the lowest positive-parity charm mesons are dynamically generated rather than quark-antiquark states.
