Where is the lightest charmed scalar meson?
Researchers of IAS-4/IKP-3 show that the mass of the lightest positive parity open charm state is 2100MeV/c2 and thus about 200 MeV/c2 below what was so far believed.
The lightest charmed scalar meson is known as the D0(2300). We show here that the parameters assigned it by the Particle Data Group are in conflict with the precise LHCb data of the decay B- to D+ π- π- which can be well described by an unitarized chiral amplitude containing a much lighter charmed scalar meson, the D0(2100). We also extract the low-energy S-wave Dπ phase from the data in a model-independent way, and show that its difference from the Dπ scattering phase shift can be traced back to an intermediate vector meson 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.