We report the first di-jet transverse momentum asymmetry measurements from Au+Au and p+p collisions at RHIC. The two highest-energy back-to-back jets reconstructed from fragments with transverse momenta above 2 GeV/c display a significantly stronger momentum imbalance in heavy-ion collisions than in the p+p reference. When re-examined with correlated soft particles included, we observe that these di-jets then exhibit a unique new feature -- momentum balance is restored to that observed in p+p for a jet resolution parameter of R=0.4, while re-balancing is not attained with a smaller value of R=0.2.
Repetition of the analysis shown in Fig. 1 with a smaller resolution parameter $R = 0.2$. Normalized $A_{J}$ distributions for Au+Au HT data (filled symbols) and p+p HT $\oplus$ Au+Au MB (open symbols). The red circles are for jets found using only constituents with $p_{T}^{Cut} > 2$ GeV/$c$ and the black squares are for matched jets found using constituents with $p_{T}^{Cut} > 0.2$ GeV/$c$.