The short-range structure of tritium and helium-3

Short-range correlations (SRCs) are pairs of highly energetic nucleons generated by hard short-distance nucleon-nucleon interactions in nuclei. 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. Previous two-nucleon knockout or ``triple-coincidence'' reactions showed that SRCs are almost exclusively np pairs, but had limited statistics and required large model-dependent final-state interaction (FSI) corrections. The E12-11-112 experiment at Jefferson Lab measured the inclusive cross section of $^3$H and $^3$He. We extract the np/pp ratio of SRCs taking advantage of the isospin structure of the mirror nuclei rather than relying on measurement of final-state nucleons. The obtained np/pp SRC ratio is an order of magnitude more precise and significantly smaller than the total np dominance observed in heavy nuclei from previous experiments. 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.