title: Evidence for triangular D3h symmetry in 12C.
abstract: We report a measurement of a new high spin Jπ=5- state at 22.4(2) MeV in 12C which fits very well to the predicted (ground state) rotational band of an oblate equilateral triangular spinning top with a D3h symmetry characterized by the sequence 0+, 2+, 3-, 4±, 5- with almost degenerate 4+ and 4- (parity doublet) states. Such a D3h symmetry was observed in triatomic molecules, and it is observed here for the first time in nuclear physics. We discuss a classification of other rotation-vibration bands in 12C such as the (0+) Hoyle band and the (1-) bending mode band and suggest measurements in search of the predicted ("missing") states that may shed new light on clustering in 12C and light nuclei. In particular, the observation (or nonobservation) of the predicted ("missing") states in the Hoyle band will allow us to conclude the geometrical arrangement of the three alpha particles composing the Hoyle state at 7.654 MeV in 12C.
authors.affiliation: School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom.
authors.forename: D J
authors.initials: DJ
authors.lastname: Marín-Lámbarri
authors.affiliation: Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, A.P. 70-543, 04510 México, D.F., Mexico.
authors.forename: R
authors.initials: R
authors.lastname: Bijker
authors.affiliation: School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom.
authors.forename: M
authors.initials: M
authors.lastname: Freer
authors.affiliation: LNS at Avery Point, University of Connecticut, Groton, Connecticut 06340-6097, USA and Wright Lab, Department of Physics, Yale University, New Haven, Connecticut 06520-8124, USA.
authors.forename: M
authors.initials: M
authors.lastname: Gai
authors.affiliation: School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom.
authors.forename: Tz
authors.initials: T
authors.lastname: Kokalova
authors.affiliation: School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom.
authors.forename: D J
authors.initials: DJ
authors.lastname: Parker
authors.affiliation: School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom.
authors.forename: C
authors.initials: C
authors.lastname: Wheldon