Speaker
Description
Prompt photons refer to photons produced at the level of partonic scatterings, both directly in the initial 2->2 interaction (\textit{direct}) prompt photons), or from the fragmentation of partons through next-to-leading order (NLO) interactions (\textit{fragmentation} prompt photons). However, the majority of photons produced in hadronic collisions originate from the decays of neutral mesons (decay photons), primarily from neutral pions, and constitute a large background for prompt photon studies. To suppress this background, many high transverse-momentum measurements of direct prompt photons utilize isolation criteria to suppress fragmentation and decay photons. However, such isolation criteria are challenging to describe in pQCD calculations, and the effective background suppression has limited phase space. Other measurements of prompt photons utilize a statistical decay-photon correction based on knowledge of the $\pi^0$ spectrum, which is likewise effective over only a limited phase space.
This phenomenlogical study presents a novel, data-driven statistical approach, to measure prompt photons in hadronic collisions, using the distribution of associated hadronic isolation energy (defined as the $p_\mathrm{T,iso}$ for all particles within a cone of R=0.4.) of photon candidates, which mitigates such limitations. The prompt photon population is identified by utilizing the difference in shape of the $p_\mathrm{T,iso}$ distribution for prompt and decay photons, and constructing a data-driven surrogate $p_\mathrm{T,iso}$ distribution for decay photons. We present an application of this approach to two different, pQCD-inspired general-purpose Monte Carlo models — PYTHIA 8.3 and Herwig 7.2 — demonstrating its robustness across different phenomenologies.
