The high momentum tail (p>k_F) of the nuclear wave function is one of its most intriguing, though elusive, parts.

Experiments conducted over the last decade have shown that in symmetric nuclei such as ¹²C, the high momentum tail (p>k_F) of the nuclear momentum distribution is dominated by nucleons belonging to Short Range Correlated (SRC) pairs and that these pairs are primarily proton-neutron (pn) pairs.

In this talk I will present new measurements of short-range correlations in medium and heavy asymmetric nuclei using the A(e,e'p) and A(e,e'pp) reactions on C, Al, Fe, and Pb. From these measurements we extracted the number of proton-proton (pp) pairs in nuclei relative to C and the number of pn pairs relative to pp pairs.  The number of pp pairs increases much more slowly than simple combinatorics, evidence that pp pairing is highly selective. Neutron-proton correlated pairs dominate over pp pairs, even in heavy asymmetric nuclei where the existence of a large number of nuclear shells allow for non-trivial pairing of pairs from different shells.