  Recent jet quenching measurements in Pb+Pb collisions at the LHC report a
significant energy imbalance of di-jets. The imbalance is found to be
compensated by a large amount of soft particles produced at large angles with
respect to the di-jet axis. This observation questions the conventional picture
of parton energy loss models, established at RHIC, which typically expect that
the radiated gluons are emitted at moderate angles close to the outgoing
parton. In this letter, we qualitatively discuss two possible contributions of
the underlying heavy-ion background that may have to be taken into account when
interpreting the recent data. We show that a large jet v_3, potentially caused
by a pathlength dependent energy loss in the presence of fluctuating initial
conditions, could contribute to the observed excess of soft particles
apparently originating from large angle in-medium radiation. In addition, the
observed excess could also be induced by multiple jets produced in the vicinity
of the leading jet, caused by a potential selection bias imposed on the di-jet
momentum imbalance.
