Away-side Distribution in a Parton Multiple Scattering Model and Background-suppressed Measures

A model of parton multiple scattering in a dense and expanding medium is described. The simulated results reproduce the general features of the data. In particular, in the intermediate trigger momentum region there is a dip-bump structure, while at higher trigger momentum the double bumps merge into a central peak. Also, a new measure is proposed to quantify the azimuthal distribution with the virtue that it suppresses the statistical fluctuations event-by-event, while enhancing the even-structure of the signal.