Femtoscopy can tell whether $Z_c(3900)$ and $Z_{cs}(3985)$ are resonances or virtual states

TL;DR

This paper proposes using femtoscopy to differentiate whether the exotic states $Z_c(3900)$ and $Z_{cs}(3985)$ are resonances, virtual states, or bound states by analyzing their correlation functions in high-energy collisions.

Contribution

It introduces a novel application of femtoscopic techniques to distinguish the nature of exotic hadronic states using correlation function analysis.

Findings

Correlation functions differ significantly among the three scenarios.

High-momentum correlation functions show distinct features in small collision systems.

Results can guide experimental efforts to identify the nature of exotic states.

Abstract

There have been extended and heated discussions on the nature of the two exotic states, $Z_c(3900)$ and $Z_{cs}(3985)$, particularly whether they are near-threshold resonances, virtual states, or bound states. In this work, we demonstrate for the first time that the femtoscopic technique can be employed to distinguish between these three scenarios. More concretely, based on the Koonin-Pratt formula with a Gaussian source, we show that the low-momentum $D^0D^{*-}$/$D^0D_s^{*-}$ correlation functions significantly differ in the three scenarios. The high-momentum results exhibit distinct characteristics in the resonant and virtual state scenarios, especially in small collision systems of 1 fm, as produced in $pp$ collisions at the LHC. We hope that these discoveries will stimulate further experimental studies and help clarify the nature of the many exotic states that have been discovered.