Speaker
Description
Hyperons are a powerful diagnostic tool that sheds light on some of the most challenging questions in contemporary physics. One is how and why the strong force confines quarks and gluons into composite systems, e.g. protons. The central question is: What happens if we replace one of the light quarks in a proton, with a heavier quark? In particular, strange systems probe the strong interaction in the confinement domain which make strange hyperons particularly interesting. Electromagnetic form factors (EMFF’s) is currently the best way to study hyperon structure. In the time-like region, the EMFF’s can be complex with a relative phase. This phase is a non-perturbative phenomenon and stems from the interference between different production amplitudes, including intermediate states. A non-zero phase polarises the final state even when the initial state is unpolarised. Hyperons have the advantage compared to protons that their polarization is experimentally accessible by the angular distributions of their decay products. However, due to experimental challenges, the studies of hyperon EMFF's are scarce and the phase has not been measured at all until now. A new, dedicated data sample collected by the BESIII experiment therefore provide new insights. In this talk, it will outlined how to measure the phase between the electric and the magnetic form factor and presented the latest results from the BESIII experiment.
