Searching for a DD¯ bound state with the ψ(3770) → γDD¯ decay

Abstract

We perform a calculation of the mass distribution in the ψ(3770) → γDD¯ decay, studying both the DD and DD¯ decays. The electromagnetic interaction is such that the tree level amplitude is null for the neutral channel, which forces the ψ(3770) → γDD¯ transition to go through a loop involving the DD→ DD¯ scattering amplitude. We take the results for this amplitude from a theoretical model that predicts a DD¯ bound state and find a DD¯ mass distribution in the decay drastically different than phase space. The rates obtained are relatively large and the experiment is easily feasible in the present BESIII facility. The performance of this experiment could provide an answer to the issue of this much searched for state, which is the analogue of the f(980) resonance.