Antiparticle
Key Stage 5
Meaning
Antiparticles are small units of antimatter.
About Antiparticles
- Many particles of matter have antimatter counterparts which have the same mass but opposite electrical charge.
- Antiparticles are generally denoted by a bar over the top of the symbol used for their matter counterpart.
- During pair-production a particle and its antiparticle appear.
- When a particle meets its antiparticle they annihilate one another producing a pair of photons.
- Most antiparticles are given the name of their counterpart particle with the addition of the prefix anti. However, the antiparticle counterpart of the electron is known as the positron.
- The existence of antiparticles is a fundamental concept in particle physics.
- Antiparticles are produced in high-energy collisions and natural radioactive decay.
- Antiparticles can be trapped and studied using magnetic fields in devices like Penning traps.
- Understanding antiparticles helps in exploring the symmetry and interactions of fundamental forces.
- The discovery of antiparticles confirmed the predictions of quantum field theory.
| Antiparticle | Symbol | Composition | Charge/e | Strangeness | Baryon Number | Lepton Number |
| \(\bar{e}\) or \(\beta^+\) | Fundamental | \(Q=+1\) | \(S=0\) | \(B=0\) | \(L=-1\) | |
| \(\bar{\nu_e}\) | Fundamental | \(Q=0\) | \(S=0\) | \(B=0\) | \(L=-1\) | |
| \(\bar{u}\) | Fundamental? | \(Q=-\frac{2}{3}\) | \(S=0\) | \(B=-\frac{1}{3}\) | \(L=0\) | |
| \(\bar{d}\) | Fundamental? | \(Q=+\frac{1}{3}\) | \(S=0\) | \(B=-\frac{1}{3}\) | \(L=0\) | |
| \(\bar{s}\) | Fundamental? | \(Q=+\frac{1}{3}\) | \(S=+1\) | \(B=-\frac{1}{3}\) | \(L=0\) | |
| \(\bar{p}\) | \(\bar{u}\bar{u}\bar{d}\) | \(Q=-1\) | \(S=0\) | \(B=-1\) | \(L=0\) | |
| \(\bar{n}\) | \(\bar{u}\bar{d}\bar{d}\) | \(Q=0\) | \(S=0\) | \(B=-1\) | \(L=0\) |