QCD prediction of jet structure in 2D trigger-associated momentum correlations and implications for multiple parton interactions

The expression "multiple parton interactions" (MPI) denotes a conjectured QCD mechanism representing contributions from secondary (semi)hard parton scattering to the transverse azimuth region (TR) of jet-triggered p-p collisions. MPI is an object of underlying-event (UE) studies that consider variation of TR $n_{ch}$ or $p_t$ yields relative to a trigger condition (leading hadron or jet $p_t$). An alternative approach is 2D trigger-associated (TA) correlations on hadron transverse momentum $p_t$ or rapidity $y_t$ in which all hadrons from all p-p events are included. Based on a two-component (soft+hard) model (TCM) of TA correlations a jet-related TA hard component is isolated. Contributions to the hard component from the triggered dijet and from secondary dijets (MPI) can be distinguished, including their azimuth dependence relative to the trigger direction. Measured $e^+$-$e^-$ and p-p fragmentation functions and a minimum-bias jet spectrum from 200 GeV p-p collisions are convoluted to predict the 2D hard component of TA correlations as a function of p-p collision multiplicity. The agreement between QCD predictions and TA correlation data is quantitative, confirming a dijet interpretation for the TCM hard component. The TA azimuth dependence is inconsistent with conventional UE assumptions.

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