Abstract
We analyze the theoretical and phenomenological considerations for the electroweak phase transition and dark matter in an extension of the Standard Model with a complex scalar singlet (cxSM). In contrast with earlier studies, we use a renormalization group improved scalar potential and treat its thermal history in a gauge invariant manner. We find that the parameter space consistent with a strong first order electroweak phase transition (SFOEWPT) and present dark matter phenomenological constraints is significantly restricted compared to results of a conventional, gauge non-invariant analysis. In the simplest variant of the cxSM, recent LUX data and a SFOEWPT require a dark matter mass close to half the mass of the Standard Model-like Higgs boson. We also comment on various caveats regarding the perturbative treatment of the phase transition dynamics.
Highlights
Explaining the excess of matter over antimatter in the present Universe is a challenge and the interface of particle and nuclear physics with cosmology
We find that the parameter space consistent with a strong first-order electroweak phase transition (SFOEWPT) and present dark matter phenomenological constraints is significantly restricted compared to results of a conventional, gauge-noninvariant analysis
We perform a GI study of the cxSM EWPT dynamics following the framework of Ref. [35] and show how use of a renormalization group (RG)-improved version of the model significantly reduces the dependence on the renormalization scale
Summary
Explaining the excess of matter over antimatter in the present Universe is a challenge and the interface of particle and nuclear physics with cosmology. We delineate various possibilities of the cxSM thermal history and analyze the effectiveness of baryon number preservation as a function of model parameters We connect these features to phenomenological signatures. While the parameter space for much larger values of mA (approaching 1 TeV) may accommodate the LUX bounds while providing for a SFOEWPT, the remaining theoretical ambiguities associated with perturbative treatments of the EWPT dynamics render this possibility less certain Our conclusions in this respect are less optimistic than those given in Ref. The latter study included a wider set of terms in the scalar potential that we consider below, a comparison of our GI, RG-improved analysis with the conventional treatment suggests that the SFOEWPT-viable parameter space associated with the wider set of operators used in Ref. The input parameters in this case are v0, mH1ð1⁄4 125 GeVÞ, mH2 , mA, δ2, and d2
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