A Differential Neutral-to-Charged Current Double-Proton Observable for Studying Short-Range Correlations in Neutrino--Argon Scattering

Two-nucleon emission is a leading uncertainty in neutrino--nucleus interaction modeling, and no neutrino measurement constrains its short-range-correlation (SRC) component. We propose such a measurement: the ratio of neutral-current to charged-current two-proton production in neutrino--argon interactions as a function of the proton-pair relative momentum. Charged-current interactions convert the abundant neutron--proton SRC pairs into visible proton pairs, whereas neutral-current interactions lack an analogous SRC contribution because proton--proton pairs are about twenty times less abundant. The ratio is therefore predicted to decrease at large relative momentum, where the charged-current SRC contribution dominates, while the neutral-current sample provides a smooth reference determined mainly by final-state interactions and multinucleon processes. Simulations predict a suppression whose magnitude scales with the SRC fraction. Flux normalization and correlated detector systematics largely cancel in the ratio, making the measurement feasible with existing liquid-argon time projection chambers. Independently of the precise SRC contribution, this observable provides the first direct experimental probe of the isospin structure of weak two-nucleon emission.