Twenty-one two-proton knockout (p,3p) cross sections were measured from neutron-rich nuclei at ∼250 MeV/nucleon in inverse kinematics. The angular distribution of the three emitted protons was determined for the first time, demonstrating that the (p,3p) kinematics are consistent with two sequential proton-proton collisions within the projectile nucleus. Ratios of (p,3p) over (p,2p) inclusive cross sections follow the trend of other many-nucleon removal reactions, further reinforcing the sequential nature of (p,3p) in neutron-rich nuclei.
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We thank the RIBF and BigRIPS teams for providing a stable beam and optimum settings over the two experimental campaigns. A. F. acknowledges support from the DFG under Grant No. SFB1245. M. G.-R. acknowledges support from the Alexander von Humboldt foundation. A. O. thanks the European Research Council for its support through ERC Grant No. MINOS-258567, the JSPS Japanese Society for the Promotion of Science for the long-term fellowship L-13520, the German DFG for its support from the SFB Grant No. 1245, and the Alexander von Humboldt Foundation for its support. K. Mo. acknowledges support from German BMBF Grant No. 05P15PKFNA. M. L. C., M. L., and V. W. acknowledge support from German BMBF Grants No. 05P15RDFN1, and No. 05P19RDFN1, as well as DFG Grant No. SFB 1245. L. X. C. and B. D. L. are supported by the Vietnam MOST through Physics Development Program Grant No. Ð TÐ LCN.25/18 and acknowledge the Radioactive Isotope Physics Laboratory of the RIKEN Nishina Center for supporting their stay during the experiment. A. J. and V. V. acknowledge support from the Spanish Ministerio de Economía y Competitividad under Contract No. FPA2017-84756-C4-2-P. U.K. participants acknowledge support from the Science and Technology Facilities Council (STFC). Collaborators from I. M. P. were supported by the National Natural Science Foundation of China and the Chinese Academy of Sciences. R. T. was supported by the JSPS Grant-in-Aid for JSPS Research Fellows JP14J08718. Zs. D., Z. K., and Zs. V. acknowledge the support from Projects No. OTKA K128947 and No. GINOP-2.3.3-15-2016-00034. C. Santamaria acknowledges support by the IPA program at the RIKEN Nishina Center.
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