Xogenesis

TL;DR

Addressing the near-coincidence of dark and baryon energy densities, the paper develops Xogenesis, a framework in which an initial dark matter asymmetry is transferred to the visible sector through mechanisms such as SU(2)$_L$ and SU(2)$_R$ sphalerons, B- and L-violating operators, or bleeding X into L. The approach relies on decoupling at a temperature $T_D$ and a thermal suppression function $f(m_X/T_D)$ to yield viable weak-scale dark matter masses without excessive tuning, producing relativistic or non-relativistic solutions for $m_X$ depending on the mechanism. It analyzes concrete scenarios, derives characteristic mass scales across parameter choices, and discusses how the symmetric component can be efficiently removed (via annihilation channels or additional fields). Overall, Xogenesis offers a mathematically consistent, testable alternative to the WIMP paradigm with a rich set of phenomenological consequences ranging from direct-detection suppression to collider-accessible new physics.

Abstract

We present a new paradigm for dark matter in which a dark matter asymmetry is established in the early universe that is then transferred to ordinary matter. We show this scenario can fit naturally into weak scale physics models, with a dark matter candidate mass of this order. We present several natural suppression mechanisms, including bleeding dark matter number density into lepton number, which occurs naturally in models with lepton-violating operators transferring the asymmetry.

Figures (5)

• Figure 1: The ratio of dark matter energy density $\rho_{\rm DM}$ to baryon energy density $\rho_{B}$ as a function of dark matter mass $m_X$ in units of the temperature at which the $B-X$ transfer decouples $T_D$, for labeled values of $T_D$. As light solution (corresponding to $m_X/T_D \sim 0$ is not shown. See Section \ref{['sec:models']} and Eq. (\ref{['eq:su2lsolution']}) for detailed explanation. The observed ratio of $\rho_{\rm DM}/\rho_B$ is $5.86$pdg.
• Figure 2: Numeric solution to Eq. (\ref{['eq:su2lsolution']}, for one, two, or three fermionic dark matter doublets ($N_X=1,2,3$) and assuming a $SU(2)_L$ sphaleron decoupling temperature $T_D = 200\mathrm{\,Ge V}\xspace$. The blue dotted line is the left-handed side of Eq. (\ref{['eq:su2lsolution']}), i.e.$f(m_X/T_D)$.
• Figure 3: Numeric solution to Eq. (\ref{['eq:singletdoubletmix']}) for $\epsilon = 0.16$ (left) and $\epsilon = 0.2$ (right). The blue dotted line is the left-handed side of Eq. (\ref{['eq:singletdoubletmix']}) and the red line is the right-handed side.
• Figure 4: The left- and right-handed sides of Eq. (\ref{['eq:lrconstraint']}) showing the numeric solutions dark matter mass $m_X$ assuming two values of $m_S/m_R$ for $T_{\rm sphaleron} = 4\mathrm{\,Te V}\xspace$ (left figure) and $200\mathrm{\,Ge V}\xspace$ (right figure). Shown are the critical solutions, when $m_S/m_R = 14(4)$ ($T_{\rm sphaleron} = 4\mathrm{\,Te V}\xspace(200\mathrm{\,Ge V}\xspace)$) and an example of solutions with a smaller value of $m_S/m_R$.
• Figure 5: Numeric solutions to Eq. (\ref{['eq:ftransfer']}). The black dotted line is the right-hand side of Eq. (\ref{['eq:ftransfer']}), while the left-hand side is shown assuming $T_D$ is $10$ (red), $25$ (blue), $50$ (orange), or $100\mathrm{\,Ge V}\xspace$ (green). For $T_D < 25\mathrm{\,Ge V}\xspace$, no solutions occur, while for larger values, two solutions exist.