Superdeformed and Triaxial States in Ca 42

Shape parametersof a weakly deformed ground-state band and highly deformed slightly triaxial sidebandin Ca42 were determined from E2 matrix elements measured in the first low-energy Coulomb excitationexperiment performed with AGATA. The picture of two coexisting structures is well reproduced by new state-of-the-art large-scale shell modeland beyond-mean-field calculations. Experimental evidence for superdeformationof the band built on 0+2 has been obtained and the role of triaxiality in the A∼40 mass region is discussed. Furthermore, the potential of Coulomb excitationas a tool to study superdeformationhas been demonstrated for the first time.