4 ms·
Minor point, but: > A test case for the bottom-up methodology is the bottom meson, a composite particle made of something called a bottom quark and another kno
by ionathan 8y ago
Minor point, but:
> A test case for the bottom-up methodology is the bottom meson, a composite particle made of something called a bottom quark and another known as a lighter quark.
I thought mesons were just a quark + an antiquark, I suppose they meant another (anti)quark that's lighter than the bottom quark?
- InclinedPlane 8y agoMesons have a wide variety. Some are quarks plus different anti-quarks (e.g. up + anti-down). Neutral mesons are not just quarks plus their anti-quarks, they are usually quantum superpositions of multiple quark/anti-quark pairs. For example, the pi-0 meson is a superposition of up + anti-up minus down + anti-down, all divided by the square root of 2 (quantum mechanics is weird). However, it gets even more complicated when spin comes into play, an up + anti-down meson could be a charged pion with 0 spin and a mass of 139 MeV or it could be a rho meson with a spin of 1 and a mass of 775 MeV.