Axion global fits with Peccei-Quinn symmetry breaking before inflation using GAMBIT

Abstract

We present global fits of cosmologically stable axion-like particle and QCD axion models in the mass range 0.1 neV to 10 eV. We focus on the case where the Peccei-Quinn symmetry is broken before the end of inflation, such that the initial value of the axion field can be considered to be homogeneous throughout the visible Universe. We include detailed likelihood functions from light-shining-through-wall experiments, haloscopes, helioscopes, the axion relic density, horizontal branch stars, supernova 1987A, white dwarf cooling, and gamma-ray observations. We carry out both frequentist and Bayesian analyses, with and without the inclusion of white dwarf cooling. We explore the degree of fine-tuning present in different models and identify parameter regions where it is possible for QCD axion models to account for both the dark matter in the Universe and the cooling hints, comparing them to specific DFSZ-and KSVZ-type models. We find the most credible parameter regions, allowing us to set (prior-dependent) upper and lower bounds on the axion mass. Our analysis also suggests that QCD axions in this scenario most probably make up a non-negligible but sub-dominant component of the dark matter in the Universe. 42 -i -5.5.1 QCD axions 43 5.5.2 DFSZ-and KSVZ-type axions 47 6 Conclusions 51 A Integrating solar models for the signal prediction in CAST 52 B Numerical implementation of the solution to the axion field equation 54 C H.E.S.S. likelihood implementation details 56 D Prior-dependence of results 58 E Overview of new capabilities 61

GAMBIT and its application in the search for physics Beyond the Standard Model

“…The core GAMBIT software is written in C ++ 11, but interfaces seamlessly with extensions and existing physics codes written in Python, Mathematica, Fortran and C. Since the release of GAMBIT 1.0.0 in 2017 [110], the most notable updates have been versions 1.1 (adding support for Mathematica) [111], 1.2 (adding support for Python and higher-spin Higgs portal models) [112], 1.3 (adding support for axion and axion-like particles) [113] and 1.4 (adding support for right-handed neutrinos) [114]. The current public release is v1.4.2.…”

“…Refs. [112,113] for recent examples), and frequentist model testing by providing information that can be used to perform statistical simulations (see Ref. [145] for a detailed example).…”

“…The GAMBIT collaboration completed a comprehensive study of axion and broader ALP theories in 2018 [113], using an extensive list of experimental constraints. These rely on the interactions of ALPs with SM matter, which can be studied in an effective field theory framework [357][358][359].…”

“…Here we provide a brief review of those constraints, referring the reader to Ref. [113] for a detailed description of the experimental likelihoods.…”

“…The numbers in brackets refer to the number of model parameters; (n + m) indicates n (largely unconstrained) fundamental parameters of the model and m (typically well-constrained) nuisance parameters. From[113].…”