## Abstract

Results are presented from a one-neutron knockout experiment at relativistic energies of ≈ 420AMeV on ^{51-55}Sc using the GSI Fragment Separator as a two-stage magnetic spectrometer and the Miniball array for gamma-ray detection. Inclusive longitudinal momentum distributions and cross-sections were measured enabling the determination of the contributions corresponding to knockout from the νp_{1/2}, νp_{3/2}, (L = 1) and νf_{7/2}, νf_{5/2} (L = 3) neutron orbitals. The observed L = 1 and L = 3 contributions are compared with theoretical cross-sections using eikonal knockout theory and spectroscopic factors from shell model calculations using the GXPF1A interaction. The measured inclusive knockout cross-sections generally follow the trends expected theoretically and given by the spectroscopic strength predicted from the shell model calculations. However, the deduced L = 1 cross-sections are generally 30-40% higher while the L = 3 contributions are about a factor of two smaller than predicted. This points to a promotion of neutrons from the νf_{7/2} to the νp_{3/2} orbital indicating a weakening of the N = 28 shell gap in these nuclei. While this is not predicted for the phenomenological GXPF1A interaction such a weakening is predicted by recent calculations using realistic low-momentum interactions V_{lowk} obtained by evolving a chiral N3LO nucleon-nucleon potential.

Original language | English |
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Article number | 191 |

Pages (from-to) | 1-10 |

Number of pages | 10 |

Journal | European Physical Journal A |

Volume | 48 |

Issue number | 12 |

DOIs | |

State | Published - 2012 |

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