# The photon content of the proton in the CT18 global analysis

### Submission summary

 Authors (as Contributors): Timothy Hobbs · Keping Xie
Submission information
Date accepted: 2022-03-23
Date submitted: 2021-07-30 03:11
Submitted by: Xie, Keping
Submitted to: SciPost Physics Proceedings
Proceedings issue: DIS2021
Ontological classification
Specialties:
• High-Energy Physics - Phenomenology
Approach: Phenomenological

### Abstract

Recently, two photon PDF sets based on implementations of the LUX ansatz into the CT18 global analysis were released. In CT18lux, the photon PDF is calculated directly using the LUX master formula for all scales, $\mu$. In an alternative realization, CT18qed, the photon PDF is initialized at the starting scale, $\mu_0$, using the LUX formulation and evolved to higher scales $\mu(>\mu_0)$ with a combined QED+QCD kernel at $\mathcal{O}(\alpha),~\mathcal{O}(\alpha\alpha_s)$ and $\mathcal{O}(\alpha^2)$. In the small-$x$ region, the photon PDF uncertainty is mainly induced by the quark and gluon PDFs, through the perturbative DIS structure functions. In comparison, the large-$x$ photon uncertainty comes from various low-energy, nonperturbative contributions, including variations of the inelastic structure functions in the resonance and continuum regions, higher-twist and target-mass corrections, and elastic electromagnetic form factors of the proton. We take the production of doubly-charged Higgs pairs, $(H^{++}H^{--})$, as an example of scenarios beyond the Standard Model to illustrate the phenomenological implications of these photon PDFs at the LHC.

Published as SciPost Phys. Proc. 8, 074 (2022)

### Submission & Refereeing History

Submission 2107.13580v1 on 30 July 2021

## Reports on this Submission

### Report

Good report, recommend for acceptance..

Minor recommendation:
Please consider to include caption to elaborate Figure 4 clearly.
Please indicate in the caption of Figure 4 that DY =DYLO to avoid confusion.

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