The photon content of the proton in the CT18 global analysis

Journal Article · Wed Jul 13 00:00:00 EDT 2022 · SciPost Physics Proceedings

DOI:https://doi.org/10.21468/SciPostPhysProc.8.074· OSTI ID:1875721

Xie, Keping ^[1]; Hobbs, Timothy ^[2]; Hou, Tie-Jiun ^[3]; Schmidt, Carl ^[4]; Yan, Mengshi ^[5]; Yuan, Chien-Peng ^[4]

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1. University of Pittsburgh
2. Fermi National Accelerator Laboratory, Illinois Institute of Technology, Southern Methodist University, Thomas Jefferson National Accelerator Facility
3. Northeastern University
4. Michigan State University
5. Peking University

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 $\mu$ . In an alternative realization, CT18qed, the photon PDF is initialized at the starting scale, \mu_0 ${\mu }_0$ , using the LUX formulation and evolved to higher scales \mu(>\mu_0) $\mu (>{\mu }_0)$ with a combined QED+QCD kernel at \mathcal{O}(\alpha),~\mathcal{O}(\alpha\alpha_s) $𝒪\left(\alpha \right),𝒪\left(\alpha {\alpha }_s\right)$ and \mathcal{O}(\alpha^2) $𝒪\left({\alpha }^2\right)$ . In the small- x $x$ 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 $x$ 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^{--}) $\left(H^{++}{H}^{--}\right)$ , as an example of scenarios beyond the Standard Model to illustrate the phenomenological implications of these photon PDFs at the LHC.

• Sponsoring Organization: USDOE
• Grant/Contract Number: AC02-07CH11359; FG02-95ER40896
• OSTI ID: 1875721
• Alternate ID(s): OSTI ID: 1831872
• Journal Information: SciPost Physics Proceedings, Journal Name: SciPost Physics Proceedings Journal Issue: 8; ISSN 2666-4003
• Publisher: Stichting SciPost
• Country of Publication: Netherlands
• Language: English