  Dihadron azimuthal correlations in 200 GeV/c Au+Au have been simulated by a
multi-phase transport (AMPT) model. Contribution from jet-medium interaction to
correlation function is obtained by subtracting the combined harmonic flow
background from the raw dihadron correlation function. Signals in centralities
of 0-10%, 20-40% and 50-80% are compared in three associated transverse
momentum ($p_{T}^{assoc}$) bins: 0.2-0.8 GeV/c, 0.8-1.4 GeV/c and 1.4-2.0
GeV/c. An obvious medium modification impact can be seen from the signal shape
change and relative jet contribution in the above events, which shows different
behaviors between central and peripheral events, and among different
$p_{T}^{assoc}$ ranges in central events. More detailed $p_{T}^{assoc}$
dependence of the derived nonflow contribution is studied in central 0-10%
events, in which a strong $p_{T}^{assoc}$ dependence of RMS width is observed.
We also calculated that relative jet contributions in peripheral and central
collisions in the above mentioned cases.
