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

Understand

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.