1. Stability of the proton
AS Level Notes

2. Stability of the proton and neutron
Decay of the Proton
A free proton (one outside a nucleus) has long been considered to be a stable particle, but recent developments of grand unification models have suggested that it might decay with a half-life of about 1031 years.
WOW! 10,000,000,000,000,000,000,000,000,000,000 years!
Particle Physicists are trying to prove that this is indeed the case.
The decay of the proton is associated with a quark transformation in which an "up" quark is converted to a "down" quark by the weak interaction .

3. Proton Decay
The decay of the proton is associated with a quark transformation in which an "up" quark is converted to a "down" quark by the weak interaction .

4. Decay of the Neutron
A free proton is virtually stable but a free neutron is comparitively very UNstable.
It will decay with a half-life of about 10.3 minutes but it is considerably more stable if combined into a nucleus.

5. Neutron Decay
The decay of the neutron involves the weak interaction as indicated in the Feynman diagrams you know.

6. Neutron Decay
The decay of the neutron is associated with a quark transformation in which a "down" quark is converted to an "up" quark by the weak interaction.