Pion

Definition

A pion is a type of meson that mediates the strong nuclear force between nucleons. Pions come in three varieties: positively charged ($\pi^+$), negatively charged ($\pi^-$), and neutral ($\pi^0$).

5 Must Know Facts For Your Next Test

1. Pions were predicted by Hideki Yukawa in 1935 as the particles responsible for mediating the strong nuclear force.
2. The mass of a pion is about 140 MeV/c², which is roughly one-seventh the mass of a proton.
3. Pions are involved in nuclear interactions and decay via the weak force, with charged pions having a mean lifetime of approximately 26 nanoseconds.
4. In particle physics experiments, pions can be produced through high-energy collisions involving protons or other hadrons.
5. The discovery of pions provided crucial evidence for Yukawa's theory and helped solidify our understanding of quantum field theory and particle interactions.

Review Questions

Related terms

Meson:

A meson is a type of hadron composed of one quark and one antiquark. Mesons participate in strong interactions.

Strong Nuclear Force:

The fundamental force responsible for holding protons and neutrons together in an atomic nucleus. It is mediated by particles like pions.

Yukawa Potential: $$V(r) = -g^2 \frac{e^{-m r}}{r}$$ A potential used to describe the interaction between nucleons mediated by pion exchange, where $g$ is the coupling constant, $m$ is the mass of the mediating particle (pion), and $r$ is distance.