One-neutron knockout from 51–55 Sc

• Published in: The European physical journal. A, Hadrons and nuclei Hadrons and nuclei, 2012-12, Vol.48 (12), Article 191
• Main Authors: Schwertel, S., Maierbeck, P., Krücken, R., Gernhäuser, R., Kröll, T., Alvarez-Pol, H., Aksouh, F., Aumann, T., Behr, K., Benjamim, E. A., Benlliure, J., Bildstein, V., Böhmer, M., Boretzky, K., Borge, M. J. G., Brünle, A., Bürger, A., Caamaño, M., Casarejos, E., Chatillon, A., Chulkov, L. V., Cortina-Gil, D., Enders, J., Eppinger, K., Faestermann, T., Friese, J., Fabbietti, L., Gascón, M., Geissel, H., Gerl, J., Gorska, M., Hansen, P. G., Jonson, B., Kanungo, R., Kiselev, O., Kojouharov, I., Klimkiewicz, A., Kurtukian, T., Kurz, N., Larsson, K., Le Bleis, T., Mahata, K., Maier, L., Nilsson, T., Nociforo, C., Nyman, G., Pascual-Izarra, C., Perea, A., Perez, D., Prochazka, A., Rodriguez-Tajes, C., Rossi, D., Schaffner, H., Schrieder, G., Simon, H., Sitar, B., Stanoiu, M., Sümmerer, K., Tengblad, O., Weick, H., Winkler, S., Brown, B. A., Otsuka, T., Tostevin, J. A., Rae, W. D. M.
• Format: Article
• Language: English
• Subjects: Hadrons; Heavy Ions; Nuclear Fusion; Nuclear Physics; Particle and Nuclear Physics; Physics; Physics and Astronomy; Regular Article - Experimental Physics
• ISSN: 1434-6001; 1434-601X
• DOI: 10.1140/epja/i2012-12191-5

Results are presented from a one-neutron knockout experiment at relativistic energies of MeV 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 , , ( L = 1 and , ( 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 to the 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 obtained by evolving a chiral N3LO nucleon-nucleon potential.