The two-channel exotic charmonium-like resonances in the mass region $(3900-4700)$ MeV

TL;DR

This paper analyzes charmonium-like resonances in the 3900-4700 MeV range using relativistic strong coupling theory, identifying conventional and exotic states, and explaining several resonances as four-quark systems.

Contribution

It presents a unified relativistic model for conventional charmonium states and introduces a coupled-channel approach to explain exotic four-quark resonances.

Findings

Identifies X(4274), X(4500), X(4700) as specific P-wave charmonium states.

Explains X(3875), X(3915), Z_{cs}(3985), X(4140) as exotic four-quark states.

Uses parameter-free relativistic string Hamiltonian for spectrum calculation.

Abstract

The resonances, containing $c\bar c$ plus $s\bar s$ (or light $q\bar q$) quarks in the mass region $(3900-4700)$ MeV, are analyzed in the relativistic strong coupling theory, with and without channel coupling phenomena. The conventional charmonium spectrum is presented, being calculated with the relativistic string Hamiltonian, which does not contain fitting parameters, while for high excitations the universal flattened confining potential is used. It is shown that $X(4274),X(4500),X(4700)$ can be identified as $3\,^3P_1, 4\,^3P_0, 5\,^3P_0$ states. The exotic states are considered using the coupled-channel (recoupling) theory, when two mesons $m_1,m_2$ transfer into another two mesons $m_3, m_4$ and back (infinite number of times), creating the four-quark systems. The resonances $X(3875), X(3915), Z_{cs}(3985), X(4140)$ can be explained in this way as the exotic four-quark states in the $S$-wave decay channels.