https://profmattstrassler.com/2022/09/09/protons-and-charm-quarks-a-lesson-from-virtual-particles/ https://profmattstrassler.com/2022/09/09/protons-and-charm-q.

https://profmattstrassler.com/2022/09/09/protons-and-charm-quarks-a-lesson-from-virtual-particles/ https://profmattstrassler.com/2022/09/09/protons-and-charm-q... It's explained better here. tl;dr; is that they are virtual particles and don't have the same mass as a "real" charm quark.