Conformal higher spin scattering amplitudes from twistor space

• Main Authors: Tim Adamo, Philipp Hähnel, Tristan McLoughlin
• Format: Article
• Language: English
• Published: SpringerOpen 2017-04-01
• Series: Journal of High Energy Physics
• Subjects: Higher Spin Symmetry; Scattering Amplitudes; Higher Spin Gravity
• Online Access: http://link.springer.com/article/10.1007/JHEP04(2017)021

Abstract We use the formulation of conformal higher spin (CHS) theories in twistor space to study their tree-level scattering amplitudes, finding expressions for all three-point M H V ¯ $$ \overline{\mathrm{MHV}} $$ amplitudes and all MHV amplitudes involving positive helicity conformal gravity particles and two negative helicity higher spins. This provides the on-shell analogue for the covariant coupling of CHS fields to a conformal gravity background. We discuss the restriction of the theory to a ghost-free unitary subsector, analogous to restricting conformal gravity to general relativity with a cosmological constant. We study the flat-space limit and show that the restricted amplitudes vanish, supporting the conjecture that in the unitary sector the S-matrix of CHS theories is trivial. However, by appropriately rescaling the amplitudes we find non-vanishing results which we compare with chiral flat-space higher spin theories.