  The method of measuring $\hat{x}_h=\hat{p}_{Ta}/\hat{p}_{Tt}$, the ratio of
the away-parton transverse momentum, $\hat{p}_{T_a}$, to the trigger-parton
transverse momentum, $\hat{p}_{T_t}$, using two-particle correlations at RHIC,
will be reviewed. This measurement is simply related to the two new variables
introduced at LHC for the di-jet fractional transverse momentum imbalance:
ATLAS $A_J=(\hat{p}_{Tt}-\hat{p}_{Ta})/(\hat{p}_{Tt}+\hat{p}_{Ta})=
(1-\hat{x}_h)/(1+\hat{x}_h)$; and CMS
$\mean{(\hat{p}_{Tt}-\hat{p}_{Ta})/\hat{p}_{Tt}}= \mean{1-\hat{x}_h}$. Results
from two-particle correlations at RHIC for $\hat{x}_h$ in p-p and A+A
collisions will be reviewed and new results will be presented and compared to
LHC results. The importance of comparing any effect in A+A collisions to the
same effect effect in p-p collisions will be illustrated and emphasized.
