Can the $$\psi (4040)$$ ψ(4040) explain the peak associated with Y(4008)?

• Main Authors: Milena Piotrowska, Francesco Giacosa, Peter Kovacs
• Format: Article
• Language: English
• Published: SpringerOpen 2019-01-01
• Series: European Physical Journal C: Particles and Fields
• Online Access: http://link.springer.com/article/10.1140/epjc/s10052-019-6615-9

Abstract We study the well-known resonance $$\psi (4040)$$ ψ(4040) , corresponding to a $$3^{3}S_{1}$$ 33S1 charm–anticharm vector state $$\psi (3S)$$ ψ(3S) , within a QFT approach, in which the decay channels into DD, $$D^{*}D$$ D∗D , $$D^{*}D^{*}$$ D∗D∗ , $$D_{s}D_{s}$$ DsDs and $$D_{s}^{*}D_{s}$$ Ds∗Ds are considered. The spectral function shows sizable deviations from a Breit–Wigner shape (an enhancement, mostly generated by $$DD^{*}$$ DD∗ loops, occurs); moreover, besides the $$c{\bar{c}}$$ cc¯ pole of $$\psi (4040)$$ 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 in the reaction $$e^{+}e^{-}\rightarrow \psi (4040)\rightarrow DD^{*}$$ e+e-→ψ(4040)→DD∗ , but in processes with $$\pi ^{+}\pi ^{-}J/\psi $$ π+π-J/ψ in the final state. A detailed study shows a related but different mechanism: a broad peak at 4 GeV in the process $$e^{+}e^{-}\rightarrow \psi (4040)\rightarrow DD^{*}\rightarrow \pi ^{+}\pi ^{-}J/\psi $$ e+e-→ψ(4040)→DD∗→π+π-J/ψ appears when $$DD^{*}$$ 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 $$c{\bar{c}}$$ cc¯ to $$DD^{*}$$ 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 $$\psi (4040)$$ ψ(4040) and $$D^{*}D$$ D∗D loops with $$\pi ^{+}\pi ^{-}J/\psi $$ π+π-J/ψ in the final state.