Three-photon productions within the $k_t$-factorization for the ATLAS-LHC data

TL;DR

This paper demonstrates that the $k_t$-factorization approach, using various unintegrated parton distribution functions, can effectively describe three-photon production data from ATLAS, matching or exceeding collinear NNLO results.

Contribution

The study applies the $k_t$-factorization framework with different UPDFs to accurately model three-photon production, showing its success compared to traditional collinear approaches.

Findings

$k_t$-factorization describes ATLAS three-photon data well.

NLO-MRW and PB UPDFs match data within uncertainties.

Results are comparable to NNLO collinear calculations.

Abstract

Recently, the ATLAS data of isolated three-photon production showed that the next-to-leading order (NLO) collinear factorization is not enough to describe experimental data. Therefore, one needs to calculate the cross section beyond the NLO, and as showed later, these data can be well described by the NNLO calculation within the collinear factorization framework. However, it is shown that the $k_t$-factorization can be quite successful in describing exclusive and high energy collision processes, henceforth we decided to calculate isolated three-photon production within this framework. In this work we use the Martin, Ryskin, and Watt unintegrated parton distribution functions (MRW UPDFs) at LO and NLO levels, in addition to parton branching (PB) UPDFs in order to calculate cross section which we utilize the KATIE parton level event generator. It will be shown that in contrast to collinear factorization, the $k_t$-factorization can describe quiet well the three-photon production ATLAS data. Interestingly our results using the NLO-MRW and PB UPDFs can cover the data within their uncertainty bands, similar to the NNLO collinear results.