The polarized photon distribution function

TL;DR

This paper computes the polarized photon distribution function using the LuxQED approach, expressing it through structure functions and analyzing uncertainties, with implications for future collider experiments.

Contribution

It introduces a method to calculate the polarized photon PDF using structure functions, providing uncertainty estimates relevant for high-energy physics.

Findings

Photon pPDF is roughly proportional to x times the unpolarized PDF.

Uncertainty in photon pPDF is up to 50% at small x, decreasing at larger x.

Results are significant for precision studies at the Electron-Ion Collider.

Abstract

We employ the LuxQED approach to compute the polarized photon PDF (photon pPDF). This approach expresses the pPDF in terms of the structure functions $g_1$ and $g_2$. Different models for the structure functions are employed according to the parameter space region. The resulting pPDF is approximately of the order of $x$ times the unpolarized PDF. The relative uncertainty in the photon pPDF reaches up to $50\%$ for $x \sim 10^{-3}$, decreasing to approximately $10\%$ for higher values of $x$. The computation of the photon pPDF will be essential for improving the precision of polarized calculations and will have fundamental implications for studies at the future Electron-Ion Collider (EIC).