tetraquarci

A tetraquark is a hypothetical type of hadron, which is a subatomic particle composed of quarks. Unlike the more familiar mesons (two quarks) and baryons (three quarks), a tetraquark consists of four quarks. Specifically, it is a bound state of two quarks and two antiquarks. The concept of tetraquarks arises from the theoretical framework of quantum chromodynamics (QCD), the theory that describes the strong nuclear force binding quarks together.

The existence of tetraquarks is predicted by some models within QCD, but their experimental verification has been a complex and ongoing challenge. They are considered exotic hadrons, meaning they do not fit into the traditional quark model classification of mesons and baryons. The internal structure of tetraquarks can be envisioned in different ways, such as a diquark-antidiquark molecule or a tightly bound four-quark system.

In 2014, the Large Hadron Collider beauty (LHCb) experiment announced the observation of a particle named Z(4430), which was later confirmed to be a tetraquark candidate. Since then, other experiments have reported evidence for additional tetraquark states, further stimulating research in this area. The study of tetraquarks provides valuable insights into the non-perturbative aspects of QCD and the complex ways quarks can bind together. Understanding these exotic particles helps to refine our knowledge of the fundamental forces and constituents of matter.