Unquenching the quark model in a non-perturbative scheme

TL;DR

This paper introduces a non-perturbative method to unquench quark models by coupling quark-antiquark states with meson-meson channels, aiming to better describe exotic states like X(3872).

Contribution

It presents a novel non-perturbative approach to include continuum effects in quark models, improving upon traditional perturbative methods.

Findings

Effective non-perturbative coupling to all relevant states.

Application to X(3872) resonance.

Comparison shows differences from perturbative results.

Abstract

In recent years, the discovery in quarkonium spectrum of several states not predicted by the naive quark model has awakened a lot of interest. A possible description of such states requires the enlargement of the quark model by introducing quark-antiquark pair creation or continuum coupling effects. The unquenching of the quark models is a way to take these new components into account. In the spirit of the Cornell Model, this is usually done by coupling perturbatively a quark-antiquark state with definite quantum numbers to the meson-meson channel with closest threshold. In this work we present a method to coupled quark-antiquark states with meson-meson channels, taking into account effectively the non-perturbative coupling to all quark-antiquark states with the same quantum numbers. The method will be applied to the study of the X(3872) resonance and a comparison with the perturbative calculation will be performed.