  Jet-medium interactions are studied via a multi-hadron correlation technique
(called "2+1"), where a pair of back-to-back hadron triggers with large
transverse momentum is used as a proxy for a di-jet. This work extends the
previous analysis for nearly-symmetric trigger pairs with the highest momentum
threshold of trigger hadron of 5 GeV/$c$ with the new calorimeter-based
triggers with energy thresholds of up to 10 GeV and above. The distributions of
associated hadrons are studied in terms of correlation shapes and per-trigger
yields on each trigger side. In contrast with di-hadron correlation results
with single triggers, the associated hadron distributions for back-to-back
triggers from central Au+Au data at $\sqrt{s_{NN}}$=200 GeV show no strong
modifications compared to d+Au data at the same energy. An imbalance in the
total transverse momentum between hadrons attributed to the near-side and
away-side of jet-like peaks is observed. The relative imbalance in the Au+Au
measurement with respect to d+Au reference is found to increase with the
asymmetry of the trigger pair, consistent with expectation from medium-induced
energy loss effects. In addition, this relative total transverse momentum
imbalance is found to decrease for softer associated hadrons. Such evolution
indicates the energy missing at higher associated momenta is converted into
softer hadrons.
