Standard Model representation

The Standard Model representations under $SU(3{)}_C\times SU(2{)}_L\times U(1{)}_Y$ are $Q_L=(3,2{)}_{1/6}$, $u_R=(3,1{)}_{2/3}$, $d_R=(3,1{)}_{-1/3}$, $L_L=(1,2{)}_{-1/2}$, $e_R=(1,1{)}_{-1}$, and $H=(1,2{)}_{1/2}$.

In one Standard Model generation, the left-handed up and down quark fields form a weak $SU(2)$ doublet of hypercharge $1/6$. Each weak component has three colours. The same field therefore counts as three doublets for weak gauge-loop contributions and two colour fundamentals for strong gauge-loop contributions. Right-handed up and down quarks are separate weak singlets.

In normalization $Q=T_3+Y$, the left quark doublet has $Y=1/6$, right up/down singlets have $2/3,-1/3$, the left lepton doublet has $-1/2$, the right charged lepton has $-1$, and the Higgs doublet has $1/2$. The alternative convention $Q=T_3+\hat{Y}/2$ uses $\hat{Y}=2Y$. Up-type Yukawa interactions use the conjugate doublet of hypercharge $-1/2$.