Hadron Physics and QCD

Our project aims to study bound-states and resonances emerging from Quantum Chromodynamics (QCD), the theory of the strong-interaction between quarks and gluons in the Standard Model of Particle Physics. While the quark model provides a qualitative picture of such hadrons consisting of mesons as quark-antiquark states and baryons as three-quark states, many exotic states not fitting simple model expectations have been observed in the last two decades.

In our study we use a discretized version of QCD called Lattice QCD along with Effective Field Theory (EFT) methods to study  hadronic systems which can be explored at the HADES experiment and at the PANDA experiment with the future FAIR facility in Darmstadt. The PANDA experiment will offer unique capabilities to map out the particle-spectrum of QCD.

Particular topics of our research are:

  • Mesons with a heavy charm-quark, which seem to have a large four-quark component and where evidence suggests that some of these states are predominantly meson-meson bound states. Pionierung works have been published by members of our group.
  • Baryons with strangeness, where PANDA will unlock a wealth of new information. We plan detailed studies of strange baryon resonances using Lattice QCD complemented by coupled-channel computations based on the chiral SU(3) Lagrangian. Previous studies focused on the chiral extrapolation of baryon masses. Global fits to the Lattice QCD data set lead the determination of a large class of low-energy constants (LEC).
  • Such LEC also play a decisive role in the determination of baryon form factors. Our previous studies focused on flavour SU(2) systems, where the important role of the isobar Delta(1232) was pointed out in the sucessful reproduction of the axial-vector form factor of the nucleon from lattice QCD data on two-flavour ensembles. First technical results on flavour SU(3) form factors are available.
  • Bound states and resonances with a heavy quark-antiquark pair close to scattering thresholds, where many unexpected states (dubbed X, Y, and Z states) are being explored  in current experiments such as Belle II, BES III, and LHCb. Here the unique energy resolution and line-scan capabilities of the PANDA experiments combined with theoretical calculations is expected to yield insights about the structure of these exotic hadrons.