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Why is the neutron slightly more massive than the proton?

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subatomic particle The Large Hadron Collider (LHC), the world's most powerful particle accelerator. At the LHC, located underground in Switzerland, physicists study subatomic particles.

The neutron is slightly more massive than the proton because of the fundamental properties of the quarks that compose them. Both particles are baryons made of three quarks: a proton consists of two up quarks and one down quark, while a neutron consists of two down quarks and one up quark.12

Because the down quark is inherently more massive than the up quark, the neutron’s specific combination of quarks results in a greater total rest mass than that of the proton. While these quarks are bound together by the strong force mediated by gluons, the mass difference between the constituent quarks is the primary reason the neutron is marginally heavier. This mass difference is significant in particle physics, as it allows a free neutron to undergo beta decay, transforming into a proton, an electron, and an antineutrino.123