Quarks are the elementary constituents of matter. The properties and interaction of quarks and gluons, which are the carriers of the strong force, are paramount in understanding the behaviour of matter at the most fundamental level. The strong force is unique among the four forces of nature for displaying the phenomenon of confinement in the low energy region: particles with a colour charge, i.e. quarks and gluons, do not occur in isolation but only in colour-neutral bound states. As two colour charges are separated, it becomes energetically favourable for a new quark-antiquark pair to appear at some point. This makes the study of strong interactions a particular challenge.
For a long time, quarks were observed to combine in hadrons (particles made up of quarks) only as quark-antiquark pairs or in groups of three (such as protons and neutrons). However, in the last two decades, new exotic hadrons have been discovered at particle accelerator experiments worldwide: multi-quark states of four or more quarks. These so-called XYZ states display striking and unexpected characteristics, and their composition in terms of quarks and gluons is still unclear.
Nora Brambilla’s research project “EFT-XYZ” aims to investigate these new forms of matter. With an unprecedented combination of quantum effective field theories (EFT) and massive computer simulations, this research will produce a breakthrough in our ability to calculate the XYZ properties in vacuum and medium, granting new insight into the fundamental strong force.
