Quarkonium
Introduction
Quarkonium refers to a flavorless meson composed of a quark and its own antiquark. The term is a portmanteau of "quark" and the "-onium" suffix, which is used to denote two-particle bound states. The most commonly known types of quarkonium include the J/ψ meson and the ϒ meson, which are composed of charm and bottom quarks, respectively.
Properties
Quarkonium states are characterized by their unique properties, which are derived from the properties of their constituent quarks. These include spin, charge, color charge, and mass. The properties of quarkonium are often used to study quantum chromodynamics (QCD), the theory of strong interactions.
Formation
Quarkonium is formed when a quark and its corresponding antiquark bind together through the strong force. This process is facilitated by the exchange of gluons, the carrier particles of the strong force. The formation of quarkonium is a complex process that involves the creation and annihilation of quarks and antiquarks.
Types of Quarkonium
There are several types of quarkonium, each named after the type of quark it contains. These include:
- Charmonium: This is a quarkonium state made up of a charm quark and its corresponding antiquark. The most well-known charmonium state is the J/ψ meson.
- Bottomonium: This is a quarkonium state made up of a bottom quark and its corresponding antiquark. The most well-known bottomonium state is the ϒ meson.
- Toponium: This is a theoretical quarkonium state made up of a top quark and its corresponding antiquark. Due to the high mass of the top quark, toponium is not expected to exist in nature.
Quarkonium in Quantum Chromodynamics
Quarkonium plays a crucial role in the study of quantum chromodynamics (QCD), the theory of strong interactions. Due to their unique properties, quarkonium states provide a testing ground for the predictions of QCD. For instance, the masses and decay widths of quarkonium states can be calculated using QCD, and these predictions can be compared with experimental results.