Unperturbed inverse kinematics nucleon knockout measurements with a carbon beam

Particle knockout scattering experiments^1,2 are fundamental for mapping the structure of atomic nuclei^2–6, but their interpretation is often complicated by initial- and final-state interactions of the incoming and scattered particles^1,2,7–9. Such interactions lead to reduction in the scattered particle flux and distort their kinematics. Here we overcome this limitation by measuring the quasi-free scattering of 48 GeV c^–112C ions from hydrogen. The distribution of single protons is studied by detecting two protons at large angles in coincidence with an intact ¹¹B nucleus. The ¹¹B detection suppresses the otherwise large distortions of reconstructed single-proton distributions induced by initial- and final-state interactions. By further detecting residual ¹⁰B and ¹⁰Be nuclei, we also identified short-range correlated nucleon–nucleon pairs^9–13 and provide direct experimental evidence for separation of the pair wavefunction from that of the residual many-body nuclear system^9,14. All measured reactions are well described by theoretical calculations that include no distortions from the initial- and final-state interactions. Our results showcase the ability to study the short-distance structure of short-lived radioactive nuclei at the forthcoming Facility for Antiproton and Ion Research (FAIR)¹⁵ and Facility for Rare Isotope Beams (FRIB)¹⁶ facilities, which is relevant for understanding the structure and properties of nuclei far from stability and the formation of visible matter in the Universe.