Beecroft Building, Department of Physics, University of Oxford, Parks Road, Oxford, OX1 3PU
Ethan Carragher, University of Oxford, Theoretical Physics
Andrei Constantin (andrei.constantin@physics.ox.ac.uk)
Abstract
The low-energy confining regime of QCD is often modelled by Nambu-Goto strings connecting quark-antiquark pairs in mesons and three (anti)quarks in baryons. The Lund string model, which takes into account only a constant string tension, successfully describes many aspects of QCD string fragmentation, but is unable to adequately explain certain features in precision LHC data. In this talk, we go beyond the Lund string model and explore the effects of the (1+1)d worldsheet degrees of freedom present on the QCD string on collider phenomenology - specifically, the massless Nambu-Goldstone boson (NGB) modes and the lightest massive excitation: a pseudoscalar "axion". Static lattice studies strongly support the existence of this axion mode, though its phenomenological consequences remain largely unexamined. We argue that worldsheet NGB and axion excitations will be highly populated in QCD strings resulting from high-energy collisions, leading to a non-uniform, dynamically varying effective string tension. The resulting modification to the standard Schwinger mechanism of string breaking via quark-antiquark production can be significant and may help explain anomalies such as the enhanced strangeness yield in high-multiplicity events.