Lepton flavor of four-fermion operator and fermion portal dark matter

Abstract

We study the ultraviolet realization of semileptonic four-fermion operator $O_{ledq}^{αβ11}$ that incorporates Majorana dark matter (DM) in both lepton-flavor-conserving (LFC) and lepton-flavor-violating (LFV) scenarios at the one-loop level via box diagram, which effectively alleviates the lower bounds on the new physics scale. The interplay between the model-independent constraints on the Wilson coefficients and DM direct detection, relic density, and collider searches in the context of fermion portal DM model with two mediators is investigated. We find that both the projected future constraint on the LFC Wilson coefficient $C_{ledq}^{2211}/Λ^2< (12.3~\text{TeV})^{-2}$ from the measurements of neutrino non-standard interaction in the next-generation neutrino oscillation experiments, and LFV constraint $C_{ledq}^{1211}/Λ^2< \left(2.2\times 10^3~\text{TeV} \right)^{-2}$ from ongoing charged-lepton-flavor-violation searches, provide a complementary exploration of the parameter space encompassing the DM mass and scalar mass. With the colored mediator mass typically around $2~\text{TeV}$, the sensitivity of the indirect constraints on the four-fermion operator could surpass those of collider searches and DM direct detection, in scenarios where the masses of the DM and scalar are close. By ensuring the correct DM relic density, however, we obtain that the collider searches and DM direct detection are more sensitive to the electroweak scale DM and scalar compared to the indirect constraints.

Figures (19)

• Figure 1: Dark loop: box diagram with dark particles in the loop.
• Figure 2: Contours of the Wilson coefficients as a function of $f_{\rm NP}$ and $m_\chi$ for the assumptions of the masses $m_\phi =2.5~\text{TeV}~(2~\text{TeV})$, and $m_F = 3~\text{TeV}~(2~\text{TeV})$ with solid (dashed) curves. The shaded regions in red (blue) color indicate exclusion for $m_S = 200~\text{GeV}~ (500~\text{GeV})$. Left: $C_{ledq}^{22 11}/\Lambda^2< (12.3~\text{TeV})^{-2}$ is depicted for $f_{\rm NP}$ in the lower axis. Right: $C_{ledq}^{12 11}/\Lambda^2< (2.2 \times 10^3$$\text{TeV})^{-2}$ and $(2.9 \times 10^4~\text{TeV})^{-2}$ are depicted for $f_{\rm NP}$ in the lower and upper axes, respectively.
• Figure 3: The Feynman diagram for Majorana DM annihilation $\chi \bar{\chi}\to \mu^+ \mu^-$.
• Figure 4: The masses $m_S$ and $m_\chi$ for different choices of the coupling $f_{\chi S}$ after fitting the DM relic density. The contour plots are displayed only for $m_\chi< m_S$.
• Figure 5: Feynman diagram for the tree-level scattering between DM and the SM quark.