Swelling of Doubly Magic <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi>Ca</mml:mi></mml:mrow><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>48</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow></mml:math> Core in Ca Isotopes beyond <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>N</mml:mi><mml:mo>=</mml:mo><mml:mn>28</mml:mn></mml:math>
M. Tanaka, M. Takechi, A. Homma, M. Fukuda, D. Nishimura, Toshio Suzuki, Y. Tanaka, T. Moriguchi, D. S. Ahn, A. Aimaganbetov, M. Amano, H. Arakawa, S. Bagchi, K.-H. Behr, N. Burtebayev, K. Chikaato, Hang Du, Shuichiro Ebata, Tomoya Fujii, N. Fukuda, H. Geißel, T. Hori, W. Horiuchi, S. Hoshino, R. Igosawa, A. Ikeda, N. Inabe, K. Inomata, K. Itahashi, T. Izumikawa, D. Kamioka, N. Kanda, Ikuma Kato, Inesh Kenzhina, Z. Korkulu, Y. Kuk, K. Kusaka, K. Matsuta, M. Mihara, E. Miyata, D. Nagae, Satoshi Nakamura, M. Nassurlla, K. Nishimuro, K. Nishizuka, Kazuhiro Ohnishi, M. Ohtake, T. Ohtsubo, Shunichiro Omika, H. J. Ong, A. Ozawa, A. Prochazka, H. Sakuraï, C. Scheidenberger, Y. Shimizu, T. Sugihara, T. Sumikama, Hiroaki Suzuki, S. Suzuki, H. Takeda, Y. Tanaka, I. Tanihata, Takehiko Wada, Kiyoshi Wakayama, S. Yagi, Takayuki Yamaguchi, R. Yanagihara, Y. Yanagisawa, K. Yoshida, T.K. Zholdybayev
Abstract
Interaction cross sections for ^{42-51}Ca on a carbon target at 280 MeV/nucleon have been measured for the first time. The neutron number dependence of derived root-mean-square matter radii shows a significant increase beyond the neutron magic number N=28. Furthermore, this enhancement of matter radii is much larger than that of the previously measured charge radii, indicating a novel growth in neutron skin thickness. A simple examination based on the Fermi-type distribution, and mean field calculations point out that this anomalous enhancement of the nuclear size beyond N=28 results from an enlargement of the core by a sudden increase in the surface diffuseness of the neutron density distribution, which implies the swelling of the bare ^{48}Ca core in Ca isotopes beyond N=28.