Charmed Protons Weigh Less Than the Sum of Their Parts
Snotnose writes:
From https://www.livescience.com/protons-charm-quark:
A proton is one of the subatomic particles that make up the nucleus of an atom. As small as protons are, they are composed of even tinier elementary particles known as quarks, which come in a variety of "flavors," or types: up, down, strange, charm, bottom and top. Typically, a proton is thought to be made of two up quarks and one down quark.
But a new study finds it's more complicated than that. Protons can also contain a charm quark, an elementary particle that's 1.5 times the mass of the proton itself. Even weirder, when the proton does contain the charm quark, the heavy particle still only carries about half the proton's mass.
The finding all comes down to the probabilistic world of quantum physics. Though the charm quark is heavy, the chance of it popping into existence in a proton is fairly small, so the high mass and small chance basically cancel each other out. Put another way, the full mass of the charm quark doesn't get taken up by the proton, even if the charm quark is there, Science News reported.
A recent Nature Podcast episode breaks this down very nicely as well. [hubie]
Journal Reference:
Richard D. Ball, Alessandro Candido, Juan Cruz-Martinez, et al. Evidence for intrinsic charm quarks in the proton [open], Nature (DOI: 10.1038/s41586-022-04998-2)
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