Physics

• Fundamental particles


  Particles that form the basic constituents of all the matter in the universe and cannot be broken down into any smaller/sub particles
• In the early days of particle physics research, the fundamental particles were considered to be the proton, the neutron and the electron
• With the help of high energy accelerators, more than two hundred particles have been identified
• The large number of these particles suggested strongly that they do not represent the most fundamental level of the structure of matter
• Standard model


  A theoretical description that can account for all the fundamental particles and the forces that cause them to interact
• Fundamental particles in the standard model

  • Quarks
  • Leptons
• Fundamental forces in the standard model

  • Strong
  • Weak
  • Gravitational
  • Electromagnetic
• The Standard Model of Fundamental Particles is an attempt to classify all of the known particles
• Fundamental particles


  • Quarks
  • Leptons
  • Bosons
• Quarks and leptons


  • They are fermions and give rise to matter
• Hadrons


  Heavyweight particles made of quarks
• Baryons


  Hadrons made of 3 quarks
• Mesons


  Hadrons made of 2 quarks (a quark and an antiquark)
• Leptons


  Lightweight fundamental particles that are not made of quarks
• Antimatter exists, with every particle having an antiparticle with the same mass but opposite charge
• Fundamental forces


  • Strong
  • Electromagnetic
  • Weak
  • Gravitational
• Fundamental forces


  • They act on different particles, have different relative magnitudes, and have different ranges
• Theoretical physicists are currently testing the idea that the four fundamental forces are different manifestations of the same force
• Bosons


  Force mediating particles that explain the action of the fundamental forces
• The force acting on one object by another is due to the exchange of these force mediating particles
• All of the forces and the reactions associated with them obey the conservation laws for energy, momentum, angular momentum and charge
• Reactions of particles also obey conservation of baryon number and conservation of strangeness
• Quarks


  Basic particles that hadrons are assembled from
• Quark flavours


  • Up (u)
  • Down (d)
  • Strange (s)
  • Charm (c)
  • Bottom (b)
  • Top (t)
• All mesons are composed of two quarks (a quark and an antiquark)
• All baryons are composed of three quarks (a combination of quarks and antiquarks)
• Standard Model of fundamental particles


  Model of the fundamental particles in physics
• Quark flavours


  • up (u)
  • down (d)
  • strange (s)
  • charm (c)
  • bottom (b)
  • top (t)
• Combinations of quark flavours (and another quark property called colour) account for the variation in all the particles in the hadron group
• Quarks do not have a direction or position
• Composition of particles


  • Mesons are composed of two quarks (a quark and an antiquark)
  • Baryons are composed of three quarks (a combination of quarks and antiquarks)
• The quark model can successfully account for all known mesons and baryons
• Meson example


  • Pion-plus, which comprises an anti-down quark and an up quark (u)
• Composition of proton and neutron


  • Proton and neutron are represented as a combination of the up and down quarks
• Quark charge


  • d has a charge of 1/3
  • u has a charge of 2/3
• The charge on the pion is 1, which means its charge is positive and equal in magnitude to the charge on an electron
• Quarks


  • They have a strong affinity for each other
  • This affinity is enabled through a new kind of charge known as colour charge
  • Colour charge comes in three shades - red, green and blue
• The colour ascribed to the quark is not a real colour as such
• All particles containing quarks are white
• Red and anti-red also give white (anti-red is a mix of green and blue)