The two particle correlation in $Z$-boson tagged events

This proceeding presents the result of the first to study of the long-range hadron correlations in \pp collisions with a constraint on collision geometry. The constraint is implemented by requiring events in which a $Z$ boson is produced. Selecting collisions with hard scattering causes the impact parameter distribution to be different from the inclusive $pp$ collision. The analysis is uses 19.4 fb$^{-1}$ of $\sqrt{s}=8$ TeV $pp$ data. The correlations between the charged-particle pairs in relative azimuthal angle over the transverse momentum range from 0.5 GeV to 5 GeV are studied as a function of the charged particle multiplicity of the event. The number of charged particle tracks and the correlation functions are corrected to account for the significant pileup contribution present in the events. The correlation in the $Z$-tagged events is found to be independent of multiplicity, and its magnitude is $8\pm6$% larger than that in inclusive $pp$ events.