Determination of $\gamma^{direct}/\pi^0$ using photon-charge particle correlation measurement in high energy heavy ion and pp collisions

Abstract

A method has been proposed for the determination of $\gamma$ to $\pi^0$ ratio in high energy pp and nucleus-nucleus collisions at large transverse momentum ($p_T$). In photon measuring device, it is proposed that shower shape analysis is made to select only cases with wide showers. These candidates come mostly from $\pi^0$. Correlation is measured between those photon candidates as trigger particles and associated charged particles above selected $p_T$. The ratio of yields of near and far angle correlation peaks for $\pi^0$ events is compared with correlation peaks from other set of events where trigger particle contains photons for direct-photon jets alongwith $\pi^0$. The comparative study in reduction of yield of near angle peak is used to extract photon fraction.