Keeping It Renormalizable: Minimal Baryogenesis induced Asymmetric Dark Matter

TL;DR

The paper presents a minimal, renormalizable scenario in which the DM asymmetry is induced by the Standard Model baryon asymmetry through chemical equilibration. It extends the SM with two fields, a complex scalar phi and an inert Higgs doublet H', stabilized by a Z4 symmetry, and uses two renormalizable transfer couplings to link the SM Higgs asymmetry to the DM sector. An asymmetric freeze-in mechanism generates the phi-dominated DM asymmetry out of equilibrium, while lambda_5 equilibrates H' and erases its symmetric component, yielding a two-component DM with a dominant phi asymmetry and a subleading H' component. The model makes concrete, testable predictions, including direct detection signals for both DM components and disappearing-tracks signatures from the light H' at colliders, with m_phi in the multi-TeV range and m_{H'} below 580 GeV, providing a path to near-term experimental tests.

Abstract

Many asymmetric dark matter scenarios have been proposed to date. Among them, perhaps the most motivated ones are those in which the dark matter asymmetry is induced from the baryon/lepton asymmetries via chemical equilibration without any new sources of CP violation. However, most of the models put forward along these lines have been excluded by now and/or are based on complicated setups. In this letter, we present a new, simple, and viable scenario. It assumes only two new fields: a scalar singlet and an inert scalar doublet, and is based only on renormalizable interactions, that slowly generate the dark matter asymmetry from the Standard Model Higgs asymmetry. The model allows for the direct detection of dark matter in the upcoming generation of experiments, and the inert doublet is predicted to be light enough to be potentially produced and observed at the LHC and future colliders, $m_{H'}<580\,{\rm GeV}$.

Figures (3)

• Figure 1: Sketch of our scenario for minimal baryogenesis induced asymmetric dark matter, based on two new fields $H'$ (a new inert Higgs doublet), and $\phi$ (a complex singlet scalar). Starting from a baryon asymmetry (generated by e.g. thermal leptogenesis) chemical equilibrium implies a SM Higgs doublet asymmetry at $T>T_{\rm EW}$, see footnote \ref{['footimportant']}. The $\lambda_{\phi^2HH'} \sim 10^{-6}$ coupling slowly creates the $\phi$ asymmetry from the SM Higgs asymmetry, thus connecting it to the baryon asymmetry of the Universe. $\lambda_5$ triggers interactions that thermalize, leading to $\mu_{H'} = \mu_H$ and provides a mass splitting between $A_0$ and $H_0$ that avoids $Z$-mediated direct detection from the inert doublet. After annihilations, we end up with a two-component dark matter scenario: a dominant asymmetric $\phi$ population and a sub-leading symmetric $H_0$ population. $\Omega_{H_0} h^2 = 0.12\,{\rm } (m_{H_0}/580\,{\rm GeV})^2$ and hence the lighter $H_0$ the more asymmetric is dark matter. We also highlight the signatures: direct detection for both dark matter components and disappearing tracks at colliders from $H^\pm$ production and decay.
• Figure 2: Parameter space in the $\lambda_{\phi^2HH'}$-$m_\phi$ plane, for various values of the doublet mass $m_{H'}$ (left) and of the neutral mass splitting $\delta m_{H_0} \equiv |m_{H_0}-m_{A}|$ (middle) that is directly related to the $\lambda_5$ coupling. For $m_\phi < 30\,{\rm TeV}$ the $\lambda_{\phi H'}$ coupling driving symmetric annihilations is expected to be perturbative EscuderoAbenza:2025cfj. In the right panel, we show the evolution for the benchmark point highlighted in the left panel as a purple dot. We can clearly see how the $\Delta \phi$ asymmetry is slowly created at early times and eventually freezes once $\phi$ becomes non-relativistic. We also see how the $\lambda_5$-induced interactions eventually enter thermal equilibrium, leading to $\Delta H' = \Delta H$.
• Figure 3: Evolution of the asymmetries in $H$, $H'$ and $\phi$ as a function of temperature for the case with $m_{H'} = 200\,{\rm GeV}$ and $\delta m_{H^0} = 450\,{\rm keV}$, i.e. $\lambda_5 =3\times 10^{-6}$, see Eq. \ref{['eq:lambda5DDcondition']}. The top panel shows the region of parameter space where the observed dark matter abundance is obtained in blue. The other panels show the temperature evolution corresponding to each benchmark. The upper sub-panel shows the interaction rates for the various processes, in particular those equilibrating the Higgs doublets ($\lambda_5$) and the scalar $(\lambda_{\phi^2 HH'})$. The vertical dotted lines indicate $T = m_\phi$.