The impact of quark many-body effects on exotic hadrons

TL;DR

This paper explores how many-body quark effects influence the formation and properties of exotic hadrons, specifically tetraquark states with two light quarks and two heavy antiquarks, using a simplified dynamical quark model.

Contribution

It demonstrates that the interplay of spin-dependent attraction and Pauli-blocking effects can explain the binding energies of $T_{cc}$ and $T_{bb}$ exotic hadrons.

Findings

A shallow bound state for $T_{cc}$ consistent with experiments.

A deep bound state for $T_{bb}$ predicted by the model.

Competition between attraction and repulsion affects exotic hadron stability.

Abstract

We investigate the exotic hadrons consisting of two light quarks and two heavy antiquarks, $(q\bar Q)$-$(q\bar Q)$. The spin-dependent term between quarks is known to give an attraction to the $ud$ spin-0 component in the isospin-0 $u\bar c d\bar c$ system, $T_{cc}$. However, the said component also gets a repulsion from the partial Pauli-blocking. By the dynamical calculation with a simplified quark model, we discuss that the competition of the two effects leads to a shallow bound state for $T_{cc}$, which is preferred from the experiment, and a deep bound state for $T_{bb}$.