Kinematical cusp and resonance interpretations of the X(2900)

Summary

We examine whether the LHCb vector udc¯s¯ state X(2900) can be interpreted as a kinematical cusp effect arising from D¯⁎K⁎ and D¯1K(⁎) interactions. The production amplitude is modelled as a triangle diagram with hadronic final state interactions. A satisfactory fit to the Dalitz plot projection is obtained that leverages the singularities of the production diagram without the need for D¯K resonances. A somewhat better fit is obtained if the final state interactions are strong enough to generate resonances, although the evidence in favour of this scenario is not conclusive.