Accommodating three low-scale anomalies (g − 2, Lamb shift, and Atomki) in the framed Standard Model

Abstract

The framed Standard Model (FSM) predicts a [Formula: see text] boson with mass around 20 MeV in the “hidden sector,” which mixes at tree level with the standard Higgs [Formula: see text] and hence acquires small couplings to quarks and leptons which can be calculated in the FSM apart from the mixing parameter [Formula: see text]. The exchange of this mixed state [Formula: see text] will contribute to [Formula: see text] and to the Lamb shift. By adjusting [Formula: see text] alone, it is found that the FSM can satisfy all present experimental bounds on the [Formula: see text] and Lamb shift anomalies for [Formula: see text] and [Formula: see text], and for the latter for both hydrogen and deuterium. The FSM predicts also a [Formula: see text] boson in the “hidden sector” with a mass of 17 MeV, that is, right on top of the Atomki anomaly [Formula: see text]. This mixes with the photon at 1-loop level and couples thereby like a dark photon to quarks and leptons. It is however a compound state and is thought likely to possess additional compound couplings to hadrons. By adjusting the mixing parameter and the [Formula: see text]’s compound coupling to nucleons, the FSM can reproduce the production rate of the [Formula: see text] in beryllium decay as well as satisfy all the bounds on [Formula: see text] listed so far in the literature. The above two results are consistent in that the [Formula: see text], being [Formula: see text], does not contribute to the Atomki anomaly if parity and angular momentum are conserved, while [Formula: see text], though contributing to [Formula: see text] and Lamb shift, has smaller couplings than [Formula: see text] and can, at first instance, be neglected there. Thus, despite the tentative nature of the three anomalies in experiment on the one hand and of the FSM as theory on the other, the accommodation of the former in the latter has strengthened the credibility of both. Indeed, if this FSM interpretation were correct, it would change the whole aspect of the anomalies from just curiosities to windows into a vast hitherto hidden sector comprising at least in part the dark matter which makes up the bulk of our universe.