A PYTHIA Simulation Study of Direct-Photon- and $\pi^{0}$-Triggered Hadron Correlations in p$+$p Collisions at $\surd $s$_{NN\, }=$ 200 GeV in Comparison to STAR Data

Heavy-ion collisions at the Relativistic Heavy Ion Collider (RHIC) have provided evidence for the existence of a new hot and dense state of matter called the Quark-Gluon Plasma (QGP). Proton-proton (p$+$p) collisions provide a baseline measurement in order to understand the properties of the QGP in heavy-ion collisions. Comparisons of jet yields in Au$+$Au collisions to those in p$+$p collisions are done to determine the attenuation of hard-scattered partons in the QGP. In this study, p$+$p collisions are simulated at a center of mass energy $\surd $s$_{NN\, }=$ 200 GeV using the PYTHIA 8.185 event generator. Jets are studied via two-particle azimuthal correlations, with the recoil jet analyzed via charged-hadron yields on the away-side ($\Delta \varphi $ approx. $\pi )$ of a $\pi ^{0}$ or a direct-photon trigger. The away-side charged-hadron per-trigger yields at mid-rapidity (\textbar $\eta $\textbar \textless 1), for transverse momenta p$_{T}^{assoc.}$ \textgreater 1.2 GeV/c, are obtained for $\pi^{0}$ and direct-photon triggers for \textbar $\eta $\textbar \textless 1 and p$_{T}^{trig.}$ \textgreater 8 GeV/c. The fraction of transverse momentum carried by triggered $\pi^{0}$ from its hard-scattered ancestors is studied to understand the energy imbalance between the triggered $\pi^{0}$ and the outgoing parton in p$+$p collisions. PYTHIA simulation results of the away-side charged-hadron yields, for $\pi^{0}$ and direct-photon triggers, are in reasonable agreement with the data collected in p$+$p collisions at the STAR experiment.