Evidence for a new particle on the worldsheet of the QCD flux tube

TL;DR

This paper introduces a novel method leveraging integrability of the worldsheet theory to compute QCD flux tube excitations, providing evidence for a new pseudoscalar particle, the worldsheet axion, through comparison with lattice data.

Contribution

It presents a new approach for calculating flux tube spectra using integrability, enabling analysis of shorter flux tubes and revealing evidence for the worldsheet axion.

Findings

Strong lattice evidence for a new pseudoscalar particle

Method allows analysis of shorter flux tubes

Quantitative agreement with lattice data

Abstract

We propose a new approach for the calculation of the spectrum of excitations of QCD flux tubes. It relies on the fact that the worldsheet theory is integrable at low energies. With this approach, energy levels can be calculated for much shorter flux tubes than was previously possible, allowing for a quantitative comparison with existing lattice data. The improved theoretical control makes it manifest that existing lattice data provides strong evidence for a new pseudoscalar particle localized on the QCD fluxtube - the worldsheet axion.