Solution
= Solution
Comparing the coefficients in the short-distance limit gives
$$
\boxed{C_{OOO}^{\rm OPE}=\frac{C_3}{C_2}}.
$$
If the operator is normalized so that $C_2=1$, its OPE coefficient equals the three-point normalization.
= Solution
Comparing the coefficients in the short-distance limit gives
$$
\boxed{C_{OOO}^{\rm OPE}=\frac{C_3}{C_2}}.
$$
If the operator is normalized so that $C_2=1$, its OPE coefficient equals the three-point normalization.