https://doi.org/10.1140/epja/i2012-12191-5
Regular Article - Experimental Physics
One-neutron knockout from 51–55 Sc
1
Physik Department E12, Technische Universität München, 85748, Garching, Germany
2
TRIUMF, 4004 Wesbrook Mall, V6T 2A3, Vancouver, Canada
3
Department of Physics & Astronomy, University of British Columbia, V6T 1Z1, Vancouver, Canada
4
Institut für Kernphysik, Technische Universität Darmstadt, 64289, Darmstadt, Germany
5
Departamento de Física de Partículas, Universidade de Santiago de Compostela, 15782, Santiago de Compostela, Spain
6
GSI Helmholtzzentrum für Schwerionenforschung, 64291, Darmstadt, Germany
7
Instituto de Estructura de la Materia, CSIC, 28006, Madrid, Spain
8
SAFE/OCL, University of Oslo, N-0316, Oslo, Norway
9
CEA, DSM/IRFU/SPhN, F-91191, Gif-sur-Yvette, France
10
University of Vigo, Vigo, E-36310, Spain
11
NSCL, Michigan State University, 48824, East Lansing, Michigan, USA
12
Experimentell Fysik, Chalmers Tekniska Högskola och Göteborgs Universitet, 412 96, Göteborg, Sweden
13
Saint Mary’s University, 923 Robie St., B3H 3C3, Halifax, Canada
14
Johannes Gutenberg Universität, 55099, Mainz, Germany
15
Paul Scherrer Institut, 5232, Villigen, Switzerland
16
Institut Pluridisciplinaire Hubert Curien, IN2P3-CNRS/Université Louis Pasteur, F-67037, Strasbourg Cedex 2, France
17
Nuclear Physics Division, Bhabha Atomic Research Centre, 400 085, Mumbai, India
18
Faculty of Mathematics and Physics, Comenius University, 84215, Bratislava, Slovakia
19
Department of Physics, University of Tokyo, Hongo, Bunkyo-ku, 113-0033, Tokyo, Japan
20
Department of Physics, Faculty of Engineering and Physical Sciences, University of Surrey, Surrey GU2 7XH, Guildford, UK
21
Garsington, OX44, Oxfordshire, UK
Received:
9
October
2012
Revised:
5
November
2012
Accepted:
1
December
2012
Published online:
20
December
2012
Results are presented from a one-neutron knockout experiment at relativistic energies of MeV on 51-55Sc 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.
© SIF, Springer-Verlag Berlin Heidelberg, 2012