title: Bonus Yangian symmetry for the planar S matrix of N=4 supersymmetric Yang-Mills theory.
abstract: Recent developments in the determination of the planar S matrix of N=4 super Yang-Mills are closely related to its Yangian symmetry. Here we provide evidence for a yet unobserved additional symmetry: the Yangian level-one helicity operator.
authors.affiliation: Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-Institut), Potsdam, Germany. nbeisert@aei.mpg.de
authors.forename: Niklas
authors.initials: N
authors.lastname: Beisert
authors.forename: Burkhard U W
authors.initials: BU
authors.lastname: Schwab