https://doi.org/10.1140/epjc/s10052-018-6388-6
Regular Article - Theoretical Physics
A grand-unified Nelson–Barr model
1
Institute for Theoretical Particle Physics, Karlsruhe Institute of Technology, Engesserstrasse 7, 76128, Karlsruhe, Germany
2
Theoretical Physics Department, CERN, 1 Esplanade des Particules, 1211, Geneva 23, Switzerland
* e-mail: robert.ziegler@cern.ch
Received:
27
August
2018
Accepted:
27
October
2018
Published online:
10
November
2018
We argue that the Nelson–Barr solution to the Strong CP Problem can be naturally realized in an E
grand-unified theory. The chiral SM fermions reside in three generations of E fundamentals together with heavy vectorlike down quarks, leptons doublets and right-handed neutrinos. CP is imposed on the Lagrangian and broken only spontaneously at high scales, leading to a mixing between chiral and vectorlike fields that allows to solve the Strong CP Problem through the Nelson–Barr mechanism. The main benefit of the E GUT structure is the predictivity in the SM fermion sector, and a perfect fit to all SM observables can be obtained despite being over-constrained. Definite predictions are made for the neutrino sector, with a Dirac CP phase that is correlated to the CKM phase, allowing to test this model in the near future.
© The Author(s), 2018
