  When protons and neutrons (nucleons) are bound into atomic nuclei, they are
close enough together to feel significant attraction, or repulsion, from the
strong, short-distance part of the nucleon-nucleon interaction. These strong
interactions lead to hard collisions between nucleons, generating pairs of
highly-energetic nucleons referred to as short-range correlations (SRCs). SRCs
are an important but relatively poorly understood part of nuclear structure and
mapping out the strength and isospin structure (neutron-proton vs proton-proton
pairs) of these virtual excitations is thus critical input for modeling a range
of nuclear, particle, and astrophysics measurements. Hitherto measurements used
two-nucleon knockout or ``triple-coincidence'' reactions to measure the
relative contribution of np- and pp-SRCs by knocking out a proton from the SRC
and detecting its partner nucleon (proton or neutron). These measurementsshow
that SRCs are almost exclusively np pairs, but had limited statistics and
required large model-dependent final-state interaction (FSI) corrections. We
report on the first measurement using inclusive scattering from the mirror
nuclei $^3$H and $^3$He to extract the np/pp ratio of SRCs in the A=3 system.
We obtain a measure of the np/pp SRC ratio that is an order of magnitude more
precise than previous experiments, and find a dramatic deviation from the
near-total np dominance observed in heavy nuclei. This result implies an
unexpected structure in the high-momentum wavefunction for $^3$He and $^3$H.
Understanding these results will improve our understanding of the short-range
part of the N-N interaction.
