Classification Of Elementary Particles

Introduction

• Elementary particle physics is the study of fundamental particles and their properties.
• An elementary particle is also called a fundamental particle. Fundamental particles are those particles which are not made up of other particles.

Classification

Parameters of Elementary Particles

• Mass: Energy and Mass are linked and interchangeable.

E = mc ²

E = m ₀ c ² + kinetic energy

1 amu = 1.67 x 10 ^-27 kg

1 amu = 931.5 MeV/ _c 2

• Charge: The particles can have charge.

Q = 0

Q = ±1

• Spin:

• The Particles having integer spin are called Bosons.

S= 0,1,2… ………

• The particles having half integer spin called fermions

S = 1/2 , 3/2 , 5/2 , ….

• The particles having spin S = 0 are known as scalar particles.

Example: - Mesons

• The particles having spin S = 1 are known as vector particles.

Example: - Photons

• The particles having spin S = 2 are known as tensor particles.

Example: - Graviton

• Parity:

• If P = 1, then particles have even parity.
• If P = -1, then particles have odd parity.
• Fermions and antifermions have opposite parity.
• Boson and anti-boson have the same intrinsic parity.
• For boson, intrinsic parity is

P = (-1) ^s

• Lifetime : Photons, electrons, neutrons and protons are stable and remaining particles are unstable.

• Particles and Antiparticles

• Particles and Antiparticles have the same mass, lifetime and spin.

• They have opposite parity, charge, isospin, magnetic moment, helicity and strangeness.
• Self-conjugate particles are identical to their antiparticles.