Precision measurements of A=3 nuclei in Hall B

Abstract

We propose a high-statistics measurement of few body nuclear structure and short range correlations in quasi-elastic scattering at 6.6 GeV from ${}^2$H, ${}^3$He and ${}^3$H targets in Hall B with the CLAS12 detector. We will measure absolute cross sections for $(e,e^{\prime }p)$ and $(e,e^{\prime }pN)$ quasi-elastic reaction channels up to a missing momentum $p_{miss}\approx 1$ GeV/c over a wide range of $Q^2$ and $x_B$ and construct the isoscalar sum of ${}^3$H and ${}^3$He. We will compare $(e,e^{\prime }p)$ cross sections to nuclear theory predictions using a wide variety of techniques and $NN$ interactions in order to constrain the $NN$ interaction at short distances. We will measure $(e,e^{\prime }pN)$ quasi-elastic reaction cross sections and $(e,e^{\prime }pN)/(e,e^{\prime }p)$ ratios to understand short range correlated (SRC) $NN$ pairs in the simplest non-trivial system. ${}^3$H and ${}^3$He, being mirror nuclei, exploit the maximum available isospin asymmetry. They are light enough that their ground states are readily calculable, but they already exhibit complex nuclear behavior, including $NN$ SRCs. We will also measure ${}^2$H$(e,e^{\prime }p)$ in order to help theorists constrain non-quasielastic reaction mechanisms in order to better calculate reactions on $A=3$ nuclei. Measuring all three few body nuclei together is critical, in order to understand and minimize different reaction effects, such as single charge exchange final state interactions, in order to test ground-state nuclear models. We will also measure the ratio of inclusive $(e,e^{\prime })$ quasi-elastic cross sections (integrated over $x_B$) from ${}^3$He and ${}^3$H in order to extract the neutron magnetic form factor $G_M^n$ at small and moderate values of $Q^2$. We will measure this at both 6.6 GeV and 2.2 GeV.

Final version of the Proposal [PR12-20-005] approved by JLab PAC48