arXiv:1002.4495v2 [nucl-th] 15 Jun 2010 Triaxial superdeformation in $^{40}$Ar Yasutaka Taniguchi, 1 Yoshiko Kanada-En’yo, 2 Masaaki Kimura, 3 Kiyomi Ikeda, 1 Hisashi Horiuchi, 4 and Eiji Ideguchi 5 $^{1}$RIKEN Nishina Center for Accelerator-Based Science, RIKEN, Wako, Saitama 351-0198, Japan $^{2}$Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto, Kyoto 606-8502, Japan $^{3}$Creative Research Initiative “Sousei, ” Hokkaido University, Sapporo, Hokkaido 001-0021, Japan $^{4}$Research Center for Nuclear Physics, Osaka University, Ibaraki, Osaka 567-0047, Japan $^{5}$Center for Nuclear Study, The University of Tokyo, Wako, Saitama 351-0198, Japan (Dated: August 29, 2018) Superdeformed (SD) states in $^{40}$Ar have been studied using the deformed-basis antisymmetrized molecular dynamics. Low energy states were calculated by the parity and angular momentum pro- jection (AMP) and the generator coordinate method (GCM). Basis wave functions were obtained by the energy variation with a constraint on the quadrupole deformation parameter β , while other quantities such as triaxiality γ were optimized by the energy variation. By the GCM calculation, an SD band was obtained just above the ground state (GS) band. The SD band involves a K π = 2 + side band due to the triaxiality. The calculated electric quadrupole transition strengths of the SD band reproduce the experimental values appropriately. Triaxiality is significant for understanding low-lying states. PACS numbers: Abstract 1