Study of $^{19}$C by One-Neutron Knockout from $^{20}$C

Abstract : The present work aims at exploring neutron-unbound states of 19C via the one-neutron knockout reaction. The invariant mass measurement in inverse kinematics was carried out with a carbon target and a 20C secondary beam at 290 MeV/nucleon. The preliminary relative energy spectrum and the parallel momentum distribution of the system of 18C + n were reconstructed from the measured momenta of the 18C fragment and decayed neutron. A new resonance was observed at Erel = 2.3 MeV, which corresponds to the unbound state of 19C at Ex = 2.9 MeV. The parallel momentum distribution for this resonance suggests a spin-parity assignment of 1/2−. Additionally, two known states were seen at Ex = 0.6 and 1.4 MeV, consistent with the 5/2+1 and 5/2+2 states, respectively.