Theoretical Hadron Physics at Uppsala University

Hadron physics is on the borderline between nuclear and high-energy physics dealing with the particles made out of quarks and gluons. Quantum chromodynamics (QCD) is the well accepted theory which describes on the fundamental level of quarks and gluons the strong interaction as one of the four elementary forces of nature. Yet there are many aspects of QCD which are not fully understood, most prominently the phenomenon of confinement - the observation that quarks and gluons cannot be isolated as single particles but rather form composite objects, the hadrons. The best known hadrons are the proton and the neutron which form the atomic nuclei, but much more types of hadrons are created and studied in particle-collision experiments. It is the purpose of hadron physics to understand the properties of hadrons such as their masses, life times, reaction rates and intrinsic composition. In theoretical hadron physics mathematical methods are developed which serve to understand and predict the properties of hadrons. A central role is played by the symmetries of QCD, most notably by the approximate chiral symmetry which is spontaneously broken.

Research activities carried out in theoretical hadron physics at Uppsala University:

• to develop effective field theories for hadronic resonances based on the symmetries of QCD
  (extensions of chiral perturbation theory)

• to explore the intrinsic structure of various hadrons
  (hadronic substructure or "directly" quarks and/or gluons)

• to investigate meson properties through near-threshold few-body nuclear reactions
  and reactions in the nuclear Coulomb field

• to describe production, decays and reactions of hadrons
  (in close contact with experiments)