2018_EJRNL_PP_RAÚL_A__BRICEÑO_1.pdf
Terbatas Ratnasari
» ITB
Terbatas Ratnasari
» ITB
The vast majority of hadrons observed in nature are not stable under the strong interaction; rather
they are resonances whose existence is deduced from enhancements in the energy dependence of
scattering amplitudes. The study of hadron resonances offers a window into the workings of quantum
chromodynamics (QCD) in the low-energy nonperturbative region, and in addition many probes of
the limits of the electroweak sector of the standard model consider processes which feature hadron
resonances. From a theoretical standpoint, this is a challenging field: the same dynamics that binds
quarks and gluons into hadron resonances also controls their decay into lighter hadrons, so a complete
approach to QCD is required. Presently, lattice QCD is the only available tool that provides the
required nonperturbative evaluation of hadron observables. This article reviews progress in the study
of few-hadron reactions in which resonances and bound states appear using lattice QCD techniques.
The leading approach is described that takes advantage of the periodic finite spatial volume used
in lattice QCD calculations to extract scattering amplitudes from the discrete spectrum of QCD
eigenstates in a box. An explanation is given of how from explicit lattice QCD calculations one can
rigorously garner information about a variety of resonance properties, including their masses, widths,
decay couplings, and form factors. The challenges which currently limit the field are discussed along
with the steps being taken to resolve them.