Relaxed Relaxion

  Abhishek Banerjee[1]  ,  Hyungjin Kim[1]  ,  Oleksii Matsedonskyi[1]  ,   Gilad Perez[1]  ,  and Marianna S. Safronova[2]  
[1] Department of Particle Physics and Astrophysics, Weizmann Institute of Science
[2] Department of Physics and Astronomy, University of Delaware

We show that the relaxion is generically stabilised at a special position in the field space, changing the parametric dependence of relaxion mass on model parameters. The relaxion mass is suppressed by additional small parameter, yielding a lighter relaxion. We revisit theoretically available relaxion parameter space, and find that the relaxion mixing angle with the Higgs boson has both maximum and minimum values. Because of parametrically suppressed relaxion mass, low energy observers might find relaxion model fine-tuned although the relaxion scenario itself is constructed in a technically natural way. We also place various phenomenological constraints on updated relaxion parameters space as well as a projected sensitivity of nuclear clock transition at the low mass range.