Baryonbaryon

Baryonbaryon refers to systems or interactions between two baryons, such as proton–proton, proton–neutron, neutron–neutron, or a baryon and a hyperon. In nuclear and hadronic physics, the baryon–baryon interaction is a central aspect of the strong force, governing the structure of ordinary nuclei and the behavior of dense matter in neutron stars. At a fundamental level these interactions arise from Quantum Chromodynamics, but their low-energy behavior is typically described with effective theories and phenomenological potentials.

The main theoretical approaches include meson-exchange models, where the force is mediated by mesons, and chiral effective field theory, which provides a systematic expansion of low-energy interactions. Lattice QCD offers ab initio calculations of baryon–baryon forces directly from QCD, though results are computationally demanding and subject to systematic uncertainties. Phenomenological baryon–baryon potentials are constrained by scattering data and by properties of bound states such as the deuteron, as well as by hypernuclear experiments when hyperons are involved.

Experimentally, nucleon–nucleon scattering data are extensive, while hyperon–nucleon and hyperon–hyperon scattering data are comparatively scarce. Evidence for baryon–baryon interactions also comes from hypernuclei and from theoretical and lattice studies. The study of these interactions informs the equation of state of nuclear matter, with implications for neutron star structure, and contributes to the search for exotic states such as dibaryons.

Related topics include baryons, the nuclear force, hyperons, and lattice QCD.