Open Access

Milena Piotrowska, Francesco Giacosa, Peter Kovacs

• We study the well-known resonance ψ(4040), corresponding to a 33S1 charm–anticharm vector state ψ(3S), within a QFT approach, in which the decay channels into DD, D∗D, D∗D∗, DsDs and D∗s Ds are considered. The spectral function shows sizable deviations from a Breit–Wigner shape (an enhancement, mostly generated by DD∗loops, occurs); moreover, besides the c ¯ c pole of ψ(4040), a second dynamically generated broad pole at 4 GeV emerges. Naively, it is tempting to identify this new pole with the unconfirmed state Y (4008). Yet, this state was not seen inthe reaction e+e− → ψ(4040) → DD∗, but in processes with π+π−J/ψ in the final state. A detailed study shows a related but different mechanism: a broad peak at 4GeV in the process e+e− → ψ(4040) → DD∗ → π+π−J/ψ appears when DD∗ loops are considered. Its existence in this reaction is not necessarily connected to the existence of a dynamically generated pole, but the underlying mechanism – the strong coupling of c ¯ c to DD∗ loops – can generate both of them. Thus, the controversial state Y (4008) may not be a genuine resonance, but a peak generated by the ψ(4040) and D∗D loops with π+π−J/ψ in the final state.