Explanation

 A proton is a fundamental particle found in the nucleus of an atom.

Its mass is relatively large compared to other particles like electrons, but smaller than some other subatomic particles.

Mesons are a type of particle made up of a quark and an antiquark.

Their mass range varies, but generally falls between that of a proton and an electron.

Some mesons, like the very heavy upsilon mesons, can have a mass significantly greater than a proton.