How Bright is the Proton? A Precise Determination of the Photon Parton Distribution Function

Explore the importance of accurately determining the photon parton distribution function (PDF) in protons for physics studies at the Large Hadron Collider. Delve into a model-independent method using electron-proton scattering data to view the ep→e+X process as an electron scattering off the proton's photon field. Examine the innovative approach of considering an imaginary, beyond the Standard Model process with a flavor-changing photon-lepton vertex, and learn how equating two different expressions of its cross section yields the photon distribution as an integral over proton structure functions. Discover how this method constrains the photon PDF to a precision of 1%–2% over a wide range of momentum fractions, showcasing the power of ep data in advancing our understanding of proton structure.