Where Is the Lightest Charmed Scalar Meson?

The lightest charmed scalar meson is known as the D-0*(2300), which is one of the earliest new hadron resonances observed at modern B factories. We show here that the parameters assigned to the lightest scalar D meson are in conflict with the precise LHCb data of the decay B- -> D+pi(-) pi(-) . On the contrary, these data can be well described by an unitarized chiral amplitude containing a much lighter charmed scalar meson, the D-0*(2100). We also extract the low-energy S-wave D pi phase of the decay B- -> D+pi(-) pi(-) - from the data in a model-independent way, and show that its difference from the D pi scattering phase shift can be traced back to an intermediate rho(-) exchange. Our work highlights that an analysis of data consistent with chiral symmetry, unitarity, and analyticity is mandatory in order to extract the properties of the ground-state scalar mesons in the singly heavy sector correctly, in analogy to the light scalar mesons f(0) (500) and K-0*(700).

Automated summary

The study reveals that the parameters assigned to the lightest scalar D meson are in conflict with experimental data, while a much lighter charmed scalar meson, the D-0*(2100), can well describe the data. In addition, it is found that an intermediate rho(-) exchange is related to the difference between the low-energy S-wave D pi phase and the D pi scattering phase shift in the analyzed data.