Pentaquark spectroscopy for the LHC

This thesis investigates the properties of exotic hadrons, specifically their mass spectra and internal structure, within the light and charmonium energy sectors. We focus on baryon resonances theorized to be pentaquark states composed of three light quarks and a heavy quark-antiquark pair. As a novel contribution to the literature, we employ the functional framework of Dyson-Schwinger and Bethe-Salpeter equations (DSEs and BSEs) and use a fully realized five-quark formulation. Our methodology builds upon solutions of quark DSEs for different flavors and mass spectra derived from two-body meson and diquark BSEs, supplemented by empirical baryon masses from the Particle Data Group.

These elements inform the central object of our study: the five-quark BSE. We apply a physically motivated Ansatz and model heavy-light pentaquarks through a comprehensive treatment of internal meson-baryon configurations, diquark-diquark-antiquark groupings, and the interplay of attractive and repulsive interactions. Most importantly, we evaluate these systems across multiplet quantum numbers and solve for states with spin J = 1 2 , 3 2 , 5 2 for both positive and negative parities.


This analysis spans both the (nnncc) and (nnscc) sectors, as well as the lightest pure light-antiquark pentaquark states (nnnnn), where n denotes an up or a down quark. To isolate the contributions of attractive and repulsive forces, we quantify the structural importance of each internal configuration. We find that incorporating repulsive interactions improves the alignment of our theoretical mass spectra with experimental observations for heavy-antiquark pentaquarks (Pc and Pcs). Ultimately, our structural analysis reveals that the heavy-antiquark pentaquarks observed at LHCb are dominated by their respective lightest heavy-light meson and baryon configurations.

Beyond the hadronic spectrum, we apply this same theoretical framework to investigate QCD contributions to flavor-changing neutral currents (FCNCs). Within this context, we calculate the corresponding quark-photon vertex incorporating W-boson exchanges alongside the Z-boson vertex. Through the calculation of transition form factors, we systematically search for signatures of lepton universality violation across different branching ratios. Specifically, we target B+ → K+l +l − decays.