  We measured the triple coincidence A(e,e'np) and A(e,e'pp) reactions on
carbon, aluminum, iron, and lead targets at Q2 > 1.5 (GeV/c)2, xB > 1.1 and
missing momentum > 400 MeV/c. This was the first direct measurement of both
proton-proton (pp) and neutron-proton (np) short-range correlated (SRC) pair
knockout from heavy asymmetric nuclei. For all measured nuclei, the average
proton-proton (pp) to neutron-proton (np) reduced cross-section ratio is about
6%, in agreement with previous indirect measurements. Correcting for
Single-Charge Exchange effects decreased the SRC pairs ratio to ~ 3%, which is
lower than previous results. Comparisons to theoretical Generalized Contact
Formalism (GCF) cross-section calculations show good agreement using both
phenomenological and chiral nucleon-nucleon potentials, favoring a lower pp to
np pair ratio. The ability of the GCF calculation to describe the experimental
data using either phenomenological or chiral potentials suggests possible
reduction of scale- and scheme-dependence in cross section ratios. Our results
also support the high-resolution description of high-momentum states being
predominantly due to nucleons in SRC pairs.
