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Aumann, T. Isobe, T. Kobayashi, T. Kubo, T. Motobayashi, T. Murakami, T. Nakamura, T. Nakashima, Y. Kondo, Y. Satou, Y. Shimizu, Y. Togano","submitted_at":"2019-01-02T17:33:51Z","abstract_excerpt":"The most neutron-rich boron isotopes 20B and 21B have been observed for the first time following proton removal from 22N and 22C at energies around 230 MeV/nucleon. Both nuclei were found to exist as resonances which were detected through their decay into 19B and one or two neutrons. Two-proton removal from 22N populated a prominent resonance-like structure in 20B at around 2.5 MeV above the one-neutron decay threshold, which is interpreted as arising from the closely spaced 1-,2- ground-state doublet predicted by the shell model. 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