Abstract
Cosmological relaxation models in which the relaxion is identified with the QCD axion, generically fail to account for the smallness of the strong CP phase. We present a simple alternative solution to this "relaxion CP problem" based on the Nelson-Barr mechanism. We take CP to be a symmetry of the UV theory, and the relaxion to have no anomalous coupling with QCD. The nonzero vacuum expectation value of the relaxion breaks CP spontaneously, and the resulting phase is mapped to the Cabibbo-Kobayashi-Maskawa phase of the Standard Model. The extended Nelson-Barr quark sector generates the relaxion "rolling" potential radiatively, relating the new physics scale with the relaxion decay constant. With no new states within the reach of the LHC, our relaxion can still be probed in a variety of astrophysical and cosmological processes, as well as in flavor experiments.
Original language | English |
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Article number | 035014 |
Number of pages | 9 |
Journal | Physical Review D |
Volume | 99 |
Issue number | 3 |
DOIs | |
Publication status | Published - 12 Feb 2019 |
Funding
We thank David Kaplan, Zohar Komargodski, Yossi Nir, Lorenzo Ubaldi, Tomer Volansky, and Jure Zupan for useful discussions. We also thank Nathaniel Craig and Claudia Frugiuele for comments on the draft, and Alfredo Urbano and Michael Dine for fruitful discussions on the quality problem. The work of G. P. is supported by grants from the United States-Israel Binational Science Foundation (BSF), European Research Council (ERC), Israeli Science Foundation (ISF), Minerva, and the Weizmann-UK Making Connections Program. Funded by SCOAP
All Science Journal Classification (ASJC) codes
- Physics and Astronomy (miscellaneous)