Measuring universality in nuclear short-range correlation interactions using ρ^- photoproduction

Nuclear Short Range Correlations (SRCs) are pairs of nucleons which exist at short relative distance and high relative momentum within the nucleus. These SRC pairs have significant impacts on nuclear structure and have been extensively studied using quasi-elastic electron-scattering data. The phenomenological Generalized Contact Formalism (GCF) has been used in recent years to connect these measurements with the ground-state properties of nuclear SRCs, using a factorized, ground-state model to predict the cross sections and event yields for these data. These interpretations rely heavily on our understanding of the electron-scattering reaction mechanisms, limiting our ability to draw conclusions about the underlying properties of SRCs. In fall of 2021, our collaboration took data in Hall D of Jefferson Lab, using a real photon beam incident on nuclear targets to independently measure the properties of nuclear SRCs. Here we present the first observation of SRC signal events in this data using quasi-elastic ρ^- meson photoproduction from correlated neutrons in deuterium, helium, and carbon nuclei, along with comparisons to the GCF predictions. We use the GCF to show consistency between the electron- and photo-scattering measurements; in this, we provide evidence for the universality of SRC properties across reactions, showing that several different hard reactions proceeding on correlated nucleons may be consistently explained using a single model.