Nuclear photoabsorption cross section ratio R = σ_L/σ_T in A=3 nuclei

Charged lepton-nuclear deep inelastic scattering cross sections depend on dimensionless structure functions, F₁ and F₂. These structure functions can be expressed in terms of σ_L and σ_T, the nuclear photoabsorption cross sections for longitudinally and transversely polarized virtual photons, respectively. The ratio R = σ_L/σ_T is critical to obtaining the F₂ structure function (or structure function ratio) from a measured nuclear cross section (or cross section ratio). Although R has only been measured for a few nuclei, assumptions about R are often made when analyzing nuclear cross section data. This is relevant to a series of experiments completed in Jefferson Lab’s Hall A during 2018. The experiments used a novel tritium target, alongside hydrogen, deuterium, and helium targets, to obtain structure function ratios from measured cross section ratios (assuming nuclear independence of R). Using a Rosenbluth separation style technique, it may be possible to use this data to obtain model-independent extractions of ΔR, the difference in R between various pairs of nuclei. This would not only add to the global dataset of R measurements, but could verify the assumptions made by the experiments in transitioning from cross sections to structure functions.