Neutral pion-hadron correlations in pp and Pb--Pb collisions with EMCal in ALICE

Two particles' correlations is a powerful tool to investigate the properties of quark-gluon-plasma(QGP) created in ultra-relativistic heavy-ion collisions. The hard partons produced in the initial stage of the collisions via the hard scattering will pass through the hot medium, the high \ensuremath{p_{\rm T}} trigger particles will generate in the surface of the medium with high probability, while the charged hadrons in away side will have a long path interaction with the hot medium affected by the nuclear modification.it's a meaningful probe to study the di-jet structure, and an important reference to investigate gamma-hadrons correlations.