Journal of High Energy Physics

, 2017:103 | Cite as

\( \mathcal{C}\mathcal{P} \) violation with an unbroken \( \mathcal{C}\mathcal{P} \) transformation

  • Michael Ratz
  • Andreas Trautner
Open Access
Regular Article - Theoretical Physics


A \( \mathcal{C}\mathcal{P} \) conserving SU(3) gauge theory is spontaneously broken to T7 by the vacuum expectation value (VEV) of a 15-plet. Even though the SU(3)-\( \mathcal{C}\mathcal{P} \) transformation is not broken by the VEV, the theory exhibits physical \( \mathcal{C}\mathcal{P} \) violation in the broken phase. This is because the SU(3)-\( \mathcal{C}\mathcal{P} \) transformation corresponds to the unique order-two outer automorphism of T7, which is not a physical \( \mathcal{C}\mathcal{P} \) transformation for the T7 states, and there is no other possible \( \mathcal{C}\mathcal{P} \) transformation. We explicitly demonstrate that \( \mathcal{C}\mathcal{P} \) is violated by calculating a \( \mathcal{C}\mathcal{P} \) odd decay asymmetry in the broken phase. This scenario provides us with a natural protection for topological vacuum terms, ensuring that \( \theta {G}_{\mu \nu }{\tilde{G}}^{\mu \nu } \) is absent even though \( \mathcal{C}\mathcal{P} \) is violated for the physical states of the model.


CP violation Discrete Symmetries Space-Time Symmetries 


Open Access

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Copyright information

© The Author(s) 2017

Authors and Affiliations

  1. 1.Department of Physics and AstronomyUniversity of CaliforniaIrvineU.S.A.
  2. 2.Bethe Center for Theoretical Physics und Physikalisches Institut der Universität BonnBonnGermany

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