Search for the15Be ground state

A two-proton knockout reaction from a ${}^{17}$C beam at 55 MeV/u was used to produce the unbound nucleus ${}^{15}$Be. No significant number of events were observed for the decay of ${}^{15}$Be into a neutron and a ${}^{14}$Be fragment. An upper limit for the ${}^{14}$Be production cross section of 0.079$\pm$0.038 mb was extracted, which is more than an order of magnitude smaller than the predicted two-proton knockout reaction cross section. Based on these results we conclude that any populated states in ${}^{15}$Be decay through three sequential neutron decays into ${}^{12}$Be, via the unbound first excited state of ${}^{14}$Be. Therefore, these states in ${}^{15}$Be must be neutron unbound by more than 1.54 MeV, which is the location of the first excited 2${}^{+}$ state in ${}^{14}$Be.