Particle physicists performing experiments at the Belle particle detector in Japan and in BESIII detector in China have found evidence of the existence of a four-quark particle named Zc(3900).
Composed of two quarks and two antiquarks.
- A hadron, a type of subatomic particle made of quarks, believed to be the first tetraquark that has been observed experimentally.
- A decay product of the previously observed anomalous Y(4260) particle.
- In turn decays into a charged pion (π±) and a J/ψ meson. This is consistent with the Zc(3900) containing four or more quarks.
What are Quarks?
A quark is an elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. Due to a phenomenon known as color confinement, quarks are never directly observed or found in isolation; they can be found only within hadrons, such as baryons (of which protons and neutrons are examples), and mesons.For this reason, much of what is known about quarks has been drawn from observations of the hadrons themselves.
What are the differnt types of Quarks?
- There are six types of quarks flavors: up, down, strange, charm, bottom, and top.
Up and down quarks have the lowest masses of all quarks. The heavier quarks rapidly change into up and down quarks through a process of particle decay. Because of this, up and down quarks are generally stable and the most common in the universe, whereas strange, charm, top, and bottom quarks can only be produced in high energy collisions (such as those involving cosmic rays and in particle accelerators).
Quarks have various intrinsic properties, including electric charge, color charge, mass, and spin. Quarks are the only elementary particles in the Standard Model of particle physics to experience all four fundamental interactions, also known as fundamental forces (electromagnetism, gravitation, strong interaction, and weak interaction), as well as the only known particles whose electric charges are not integer multiples of the elementary charge.
Quarks have three kinds of charges which are characterized by a quantum number called colour (as three kinds of primary colours exist).
What is Quantum Chromodynamics or QCD?
- The theory describing the strong interaction of quarks is called Quantum Chromodynamics or QCD.
What is antiquark?
- For every quark flavor there is a corresponding type of antiparticle, known as anantiquark, that differs from the quark only in that some of its properties have equal magnitude but opposite sign.