Noun
up quark (plural up quarks)
(physics) A quark having a fractional electric charge of
+
2
3
{\displaystyle +{\frac {2}{3}}}
and a mass of about 1.5 to 4 MeV.Symbol:
u
{\displaystyle u}
A neutron composed of two down quarks and an up quark, decays to a proton composed of a down quark and two up quarks, for example. Source: Internet
At the quark level, W − emission turns a down quark into an up quark, turning a neutron (one up quark and two down quarks) into a proton (two up quarks and one down quark). Source: Internet
For example, an up quark with a spin of + 1 2 along the z axis is denoted by u↑. Source: Internet
Neutrons consist of one up quark and two down quarks. Source: Internet
The similarity in mass can be explained roughly by the slight difference in mass of up quark and down quark composing the nucleons. Source: Internet