Exploring S-Wave Threshold Effects in QCD: A Heavy-Light Approach

TL;DR

This paper investigates how S-wave threshold effects influence heavy-light meson systems in QCD, using lattice QCD to analyze the dynamics near physical strange-quark masses, providing a practical approach for future studies.

Contribution

It introduces a lattice QCD method to study threshold effects in heavy-light mesons by varying strange-quark mass with minimal computational effort.

Findings

Demonstrates how threshold effects manifest in heavy-light systems.

Provides a feasible lattice QCD approach for threshold analysis.

Suggests minimal computational cost for future research.

Abstract

QCD exhibits complex dynamics near S-wave two-body thresholds. For light mesons, we see this in the failure of quark models to explain the $f_0(500)$ and $K_0^*(700)$ masses. For charmonium, an unexpected $X(3872)$ state appears at the open charm threshold. In heavy-light systems, analogous threshold effects appear for the lowest $J^P = 0^+$ and $1^+$ states in the $D_s$ and $B_s$ systems. Here we describe how lattice QCD can be used to understand these threshold dynamics by smoothly varying the strange-quark mass when studying the heavy-light systems. Small perturbations around the physical strange quark mass are used so to always remain near the physical QCD dynamics. This calculation is a straightforward extension of those already in the literature and can be undertaken by multiple lattice QCD collaborations with minimal computational cost.