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

TL;DR

This study investigates the $ ext{ψ}(4040)$ resonance using a quantum field theory approach, revealing a dynamically generated broad pole near 4 GeV that could explain the observed peak associated with the unconfirmed $Y(4008)$ state.

Contribution

The paper demonstrates that the $Y(4008)$ peak may result from loop effects of $ ext{ψ}(4040)$ and $D^{ ext{*}}D$ interactions, challenging its interpretation as a genuine resonance.

Findings

A broad pole at 4 GeV is dynamically generated.

The $Y(4008)$ peak can be explained by loop effects without a new resonance.

The mechanism involves strong coupling of $car{c}$ to $D^{ ext{*}}D$ loops.

Abstract

We study the well-known resonance $\psi(4040)$, corresponding to a $3^{3}S_{1}$ charm-anticharm vector state $\psi(3S)$, within a QFT approach, in which the decay channels into $DD$, $D^{\ast}D$, $D^{\ast}D^{\ast}$, $D_{s}D_{s}$ and $D_{s}^{\ast}D_{s}$ are considered. The spectral function shows sizable deviations from a Breit-Wigner shape (an enhancement, mostly generated by $DD^{\ast}$ loops, occurs); moreover, besides the $c\bar{c}$ pole of $\psi(4040)$, 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 $e^{+}e^{-}\rightarrow\psi(4040)\rightarrow DD^{\ast}$, but in processes with $\pi^{+}\pi^{-}J/\psi$ in the final state. A detailed study shows a related but different mechanism: a broad peak at $4$ GeV in the process $e^{+}e^{-}\rightarrow\psi(4040)\rightarrow DD^{\ast }\rightarrow\pi^{+}\pi^{-}J/\psi$ appears when $DD^{\ast}$ 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 $c\bar{c}$ to \ $DD^{\ast}$ loops - can generate both of them. Thus, the controversial state $Y(4008)$ may not be a genuine resonance, but a peak generated by the $\psi(4040)$ and $D^{\ast}D$ loops with $\pi^{+}\pi^{-}J/\psi$ in the final state.