Abstract
We propose a minimal realization of the Peccei Quinn mechanism in a realistic SU(5) model, where the axion mass is directly connected to the grand-unification scale. By taking into account constraints from proton decay, collider searches and gauge coupling unification, we predict the axion mass: $m_a \in [4.8, 6.6]$ neV. The upper bound can be relaxed up to $m_a < 330$ neV, at the cost of tuning the flavour structure of the proton decay operators. The predicted mass window will be complementarily probed by the axion dark matter experiments ABRACADABRA and CASPER-Electric, which could provide an indirect evidence for the scale of grand unification before the observation of proton decay.
Highlights
It is a widespread belief that the standard model (SM) of particle physics should break down at some intermediate energy between the electroweak and the Planck scale
Including the detailed information from gauge coupling unification available in the WGG þ 24F model, we are able to set a lower bound on the axion mass from the nonobservation of electroweak-triplet states at Large Hadron Collider (LHC), predicting the following axion mass: ma ∈ 1⁄24.8; 6.6 neV, where the upper bound holds in the absence of tuning of fermionic mixing
An axion in the neV mass range can make 100% of dark matter (DM), if the initial field value θi is of order 10−2.7 In this cosmological scenario, isocurvature quantum fluctuations of a massless axion field during inflation may leave an imprint in the temperature fluctuations of the cosmic microwave background (CMB) [53,54], whose amplitude is stringently constrained by observations
Summary
It is a widespread belief that the standard model (SM) of particle physics should break down at some intermediate energy between the electroweak and the Planck scale. Including the detailed information from gauge coupling unification available in the WGG þ 24F model, we are able to set a lower bound on the axion mass from the nonobservation of electroweak-triplet states at LHC, predicting the following axion mass: ma ∈ 1⁄24.8; 6.6 neV, where the upper bound holds in the absence of tuning of fermionic mixing. Furnished with this result, we provide the axion coupling to the SM fields and estimate the sensitivity of future axion DM experiments such as ABRACADABRA [28] and CASPEr [29,30] in the relevant mass window
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