# Does weak interaction always come in decays?

Well, essentially I'm confused about how weak nuclear force works. Decay is usually mentioned in studying weak nuclear force, so does weak force always work in decays? If so, is all decay is based on the weak nuclear force?

Some decays are caused by the electromagnetic force. For example, the neutral pion, $\pi^0$, made of a superposition of $u\bar{u}$ and $d\bar{d}$ decays by annihilation of the quark-antiquark into 2 photons. Other decays happen through the strong interaction. For example the neutral Delta baryon, $\Delta^0$, made of $udd$, i.e. the same make-up as the neutron, but the constituent are in a higher energy state than the neutron. The decay $\Delta^0 \to \pi^- + p$ happens through the strong interaction. I'll add the Feynman diagram later.