Proton Along with neutrons , protons make up the nucleus, held together by the strong force . The proton is a baryon and is considered to be composed of two up quarks and one down quark.
Experiments are underway to see if such decays can be detected.
Decay of the proton would violate the conservation of baryon number , and in doing so would be the only known process in nature which does so. When we say that a proton is made up of two up quarks and a down, we mean that its net appearance or net set of quantum numbers match that picture. The nature of quark confinement suggests that the quarks are surrounded by a cloud of gluons , and within the tiny volume of the proton other quark-antiquark pairs can be produced and then annihilated without changing the net external appearance of the proton. Such a long half-life is exceedingly difficult to measure, but there seems to be some hope of doing so in deep mine experiments such as those in the Soudron iron mines in Minnesota. The neutron is a baryon and is considered to be composed of two down quarks and one up quark.