Projects per year
Abstract
The relaxion mechanism is a novel solution to the hierarchy problem. In this first statistical analysis of the relaxion mechanism, we quantify the relative plausibility of a QCD and a nonQCD relaxion model versus the Standard Model with Bayesian statistics, which includes an automatic penalty for finetuning. We find that in light of the hierarchy between the weak and Planck scales, relaxion models are favoured by colossal Bayesfactors. Constraints upon e.g., the vacuum energy during relaxation, however, shrink the Bayesfactors such that relaxion models are only slightly favoured. Including the bounds on θ_{QCD} shatters the plausibility of the QCD relaxion model as it typically yields θ_{QCD} ≫ 0. Finally, we augment our models with scalarfield inflation and consider measurements of inflationary observables from BICEP/Planck. We find that, all told, the Standard Model is favoured by huge Bayesfactors as the relaxion models require finetuning such that the Hubble parameter is less than the height of the periodic barriers. Thus, whilst we confirm that relaxion models could solve the hierarchy problem, we find that their unconventional cosmology is at odds with their plausibility.
Original language  English 

Article number  100 
Number of pages  26 
Journal  Journal of High Energy Physics 
Volume  2016 
Issue number  8 
DOIs  
Publication status  Published  1 Aug 2016 
Keywords
 Beyond Standard Model
 Higgs Physics
Projects
 1 Finished

ARC Centre of Excellence for Particle Physics at the TeraScale
Balazs, C., Barberio, E., Bell, N., Gherghetta, T., Limosani, A., Sevior, M., Taylor, G., Thomas, A., Varvell, K., Volkas, R., Williams, A. G., Yabsley, B., Young, R. D., Clarke, A., Jakobs, C., Kruse, M., Meroni, C., Parker, M. & Trodden, M.
Australian Research Council (ARC)
1/01/11 → 31/12/18
Project: Research