$2\alpha+t$ cluster structure in $^{11}$B
  The cluster structures of the excited states in $^{11}$B are studied by analyzing the isoscalar monopole and quadrupole strengths in the $^{11}$B($d$,$d'$) reaction at $E_d=200$ MeV. The excitation strengths are compared with the predictions by the shell-model and antisymmetrized molecular-dynamics (AMD) calculations. It is found that the large monopole strength for the $3/2^-_3$ state at $E_x=8.56$ MeV is well described by the AMD calculation and is an evidence for a developed $2\alpha+t$ cluster structure. 
T. Kawabata, H. Akimune, H. Fujita, Y. Fujita, M. Fujiwara, K. Hara,   K. Hatanaka, M. Itoh, Y. Kanada-En'yo, S. Kishi, K. N...