Phenomenology of relaxion-Higgs mixing

Flacke, Thomas (Center for Theoretical Physics of the Universe, Institute for Basic Science (IBS), Daejeon, 34051, Korea) (Department of Physics, Korea University, Seoul, 136-713, Korea) ; Frugiuele, Claudia (Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot, 76100, Israel) ; Fuchs, Elina (Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot, 76100, Israel) ; Gupta, Rick (Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot, 76100, Israel) ; Perez, Gilad (Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot, 76100, Israel)

14 June 2017

Abstract: We show that the relaxion generically stops its rolling at a point that breaks CP leading to relaxion-Higgs mixing. This opens the door to a variety of observational probes since the possible relaxion mass spans a broad range from sub-eV to the GeV scale. We derive constraints from current experiments (fifth force, astrophysical and cosmological probes, beam dump, flavour, LEP and LHC) and present projections from future experiments such as NA62, SHiP and PIXIE. We find that a large region of the parameter space is already under the experimental scrutiny. All the experimental constraints we derive are equally applicable for general Higgs portal models. In addition, we show that simple multiaxion (clockwork) UV completions suffer from a mild fine tuning problem, which increases with the number of sites. These results favour a cut-off scale lower than the existing theoretical bounds.


Published in: JHEP 1706 (2017) 050
Published by: Springer/SISSA
DOI: 10.1007/JHEP06(2017)050
arXiv: 1610.02025
License: CC-BY-4.0



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