Predicted Measurements of the Tensor-to-Scalar Transition in the CLAS12 Nuclear Targets Experiment

TL;DR

This paper predicts the tensor-to-scalar transition in short-range correlated nucleon pairs using GCF theory and simulations for the CLAS12 experiment, aiming to observe changes in pair abundances at high momenta.

Contribution

It provides a detailed simulation-based prediction that the CLAS12 experiment can detect the tensor-to-scalar transition in nucleon pairs at high momenta.

Findings

Simulations show sufficient statistical precision for observing the transition.

Expected increase in pp pairs and change in pn pairs with momentum.

Potential to conclusively demonstrate the tensor-to-scalar transition.

Abstract

Short-range correlated (SRC) nucleon pairs, which are strongly interacting nucleons at short inter-particle distances, can reveal properties of the effective nucleon-nucleon (\textit{NN}) interaction at short distance scales. The relative abundance of proton-proton (\textit{pp}) pairs and proton-neutron (\textit{pn}) pairs, for example, is sensitive to the tensor contribution to the \textit{NN} interaction. Generalized Contact Formalism (GCF) theory, when used with realistic phenomenological \textit{NN} potential models, predicts a transition from a tensor-dominated regime -- at relative momenta of approximately 400~MeV/\textit{c} where \textit{pp} pairs are suppressed relative to \textit{pn} pairs -- to a scalar-dominated regime at higher momenta with no preferred isospin projection. While an increase in the prevalence of \textit{pp} pairs with increasing momentum has been observed in a few experiments, difficulties associated with neutron detection have so far hindered the observation of a corresponding reduction in the abundance of \textit{pn} pairs. High-precision measurements showing a simultaneous increase in the abundance of \textit{pp} pairs and change in the abundance of \textit{pn} pairs with increasing momentum would conclusively demonstrate the existence of the tensor-to-scalar transition. In this work, we study the potential impact of the recently conducted Nuclear Targets Experiment at the CLAS12 detector at Jefferson Lab, using GCF simulations. We model the expected yields and relevant observables for a carbon target with a beam energy of 6 GeV and show that sufficient statistical precision can be obtained from the experimental data, both for \textit{pp} and \textit{pn} pairs, to observe the tensor-to-scalar transition.