Elementary particles

The structureless indivisible particle that is not made of other particles is known as elementary particles. It is regarded as elementary in the sense that it cannot be explained as a system of other elementary particles. The first four elementary particles around 1938 were electrons, protons, neutrons and neutrinos. Later on, several other particles have been discovered. Some of them are muon (A) pion (π), Kaun (K), sigma (E), tauon, lambda, Xi , Omega etc

Antiparticles.

An antiparticle of a particle is another particle having the same mass but opposite charge and spin to that particle. The antiparticles of the massless and chargeless particle are determined. by their spin. E.g: Neutrino has a clockwise spin and antineutrino has an anti-clockwise spin. Antielectrons or position, antiprotons, antineutrons etc. are some .

Annihilation 

A phenomenon in which a particle and antiparticle come together then vanish simultaneously with the lost mass becoming energy is called Annihilation. It is used to denote the process that occurs when a subatomic particle collides with its respective antiparticle.

Pair production

A pair of election and position may be formed when the matter is irradiated with electromagnetic Radiation having. 1.0e  MeV or more. The process called pair production.

It is the opposite process of annihilation. When a target is irradiated by a photon of sufficient energy a pair of antiparticles may be produced. The process of called pair /production.

Classification of elementary particles

• Lepton




• Quarks




• Mediator particles

Lepton 

• Meaning - lightest particle.




• The leptons do not have a measurable size or internal structure and they cannot be further broken into smaller constituent hence they are elementary particles.




• Respond to weak and electromagnetic interactions and has aMass lesser than that of neutrons.




• They are all fermions of spin 1/2.




• It has electric charges of either (-1) or zero




• There are 6 leptons in the present structure, the electron and fall particles, and their associated neutrons.

Quarks: 

•  Elementary particles that make up hadrons




• The quark model was proposed independently by Murray Gell-Mann and G. Zweig in 1963.




• The quarks model has a fractional electric charge value. +2/3 e or -1/3 e




• In an observable particle, the fractional charges of quark in the particle add up to an integer charge for the combination.




• No quark has been detected experimentally so far because they are not present independently outside hadron.

 Mediator particles 

• Mediator particles are those particles that carry the forces  acting on matter and antimatter. 

• also called force carriers.

• These particles. carry the basic forces in nature which are the electromagnetic, the gravitational, the strong, and the weak.

Hadrons 

 heavy particles that interact via the strong nuclear force and hence they are said to be strongly interacting particles.

Divided into two groups

• Baryons (composed of 3 quarks)




• Mesons( Quark and antiquark)

Baryons

•  heaviest particles including nucleons




•  have half-integral spins (1/2, 3/2-) and are therefore fermions.




•  Baryon's heavier than nucleus are collectively called hyperons




•  respond to weak, strong, and electromagnetic interactions.




• Each baryon has an antibaryon.

Mesons

• A particle having a mass intermediate between that of an electron and the proton is called a meson.




• The Japanese physicist Hideki Yukawa predicted the existence of meson mediating the strong nuclear force.




• All mesons have zero or integral spin an integral and so they are bosons




• All the mesons are unstable.