Introduction of particles, antiparticles, matter and antimatter
In this particular article Introduction of particles, antiparticles, matter and antimatter, we are going to discuss some basic information of particles and antiparticles. Their history. Along with the description of matter and antimatter. We will also discuss the fact that why muon is not a meson particle in easiest way possible.
Particles and antiparticles
Dirac in 1928 predicted theoretically that a particle must exist along with electron in nature whose mass and spin are same as that of electron and magnitude of charge of that particle should be equal to that of electron charge. But opposite in nature (spin)i.e. charge of that particle should be +e = 1.6 ×10⁻¹⁹ C. This particle is said to be Antiparticle of electron named positron. Experimentally this particle was discovered in 1932 by Carl Anderson in cosmic rays.
Now it is assumed that each elementary particle has its own Antiparticle. The mass, spin , mean life (if unstable) and magnitude of charge (if they have) of Antiparticle are same as that of corresponding particle. But the nature of charged Antiparticle is just opposite to the particle. Similarly thr alignment or antialignment between its spin and magnetic moment is also opposite to that of particle.
Particle-antiparticle pairs can annihilate each other, producing γ photons. This process is called annihilation. Since charges of the particle and its Antiparticle are opposite , total charge is conserved.
Thus antiparticle is defined as the particle having same mass, spin , mean life (if unstable) . And magnitude of charge (if it has) opposite in nature the alignment or antialignment between its spin and magnetic moment is also opposite to that of particle. And also when annihilates with its antiparticle produces high energy photons.
The antiparticle is described by a placing a bar on symbol used for its particle. For example, for antineutrino the symbol is v. I.e bar on neutrino,
Some particles are antiparticle of itself, such as photon (γ), π⁰ and η meson.
Although mass and spin of particles and their antiparticles are same, yet many other following quantities of particles and antiparticles have same magnitude but opposite signs.
- Electric charge (Q)
- Lepton number (L)
- Baryon number (B)
- Strangeness (S)
- Charm number
- Isospin (I₃)
The mass, spin, identity, mean life of some particles and their antiparticles are given in following table-
Matter and antimatter
Matter is made up of atoms and molecules and they are composed of electrons (e⁻), protons (p) and neutrons (n). All the three particles have their own antiparticle. These are positron (e⁺), antiprotons (p—) and antineutron, then it would be called antinucleus. If positrons are moving around the antineutrons, then it would make a structure of antiatom. For example, structure of hydrogen and antihydrogen are shown in fig. As hydrogen is a stable atom, so antihydrogen should also be a stable anti atom. In 1996 some antihydrogen atoms have been produced for a nanosecond in CERN laboratory. In this way the matter made from antiatom would be called antimatter.
Our universe consists of galaxies, stars, planets and all are made up of matter. Therefore it can be imagined that there could be antiuniverse parallel to our universe which consists of antimatter. But we did not find any experimental evidence of this imagination up till now.
Muon is not a meson particle:
Muon particle was discovered in 1936 by Anderson and Neddermeyer in cosmic rays. From the historical point of view, before the discovery of muon, Yukawa theoretically proved that the carrier of the strong interaction is a particle whose mass is about 200-300 me. This particle was then called meson. When muon particle was discovered, it was through by some scientists that muon particle is the same mason particle. But afterwards it was proved experimentally that muon is not the meson particle. This is because muon does not take part in strong interactions. Whereas meson is a carrier of strong interaction. In addition to meson is a boson particle of spin I, whereas muon is a fermion particle of spin 1/2.
In this article we have covered the topics of basics of particles and antiparticles, matter and antimatter etc