Fermionic Dark Matter and New Scalar Production in $e^+e^- \to H^+H^-$ at Colliders

TL;DR

This work analyzes $e^+e^- \to H^+H^-$ production in the scotogenic model, where the cross section receives tree-level contributions from $\gamma$ and $Z$ exchanges and a $t$-channel exchange of singlet Majorana fermions $N_{1,2,3}$. The authors impose stringent constraints from neutrino masses and mixing, dark matter relic density, direct detection, and lepton flavor violation, identifying viable parameter regions typically with TeV-scale new states. They find that the $N_{1,2,3}$-mediated diagrams dominate the cross section, with the photon and $Z$-mediated parts subdominant, and they study the energy dependence of the cross section for representative benchmarks. The results imply that future high-energy $e^+e^-$ colliders can test the scotogenic scenario and constrain the couplings and masses of the new fermions and scalars, thereby probing fermionic dark matter and radiative neutrino-mass generation in a collider context.

Abstract

We investigate the pair production process $e^+e^- \to H^+H^-$ in the framework of the scotogenic model. The production mechanism receives contributions at tree level from photon and $Z$-boson exchange, as well as from $t$-channel exchange of the new singlet right-handed fermions $N_{1,2,3}$. where neutrino masses are generated radiatively and one of the singlet right-handed fermions serves as a viable dark matter candidate. We evaluate the individual contributions of these diagrams and compute the total production cross section after imposing all relevant theoretical and experimental constraints on the model parameters, including those associated with dark matter relic abundance and direct detection limits. Our results demonstrate that the dominant contribution to the cross section originates from the exchange of the singlet fermions $N_{1,2,3}$, particularly from the dark matter component of the spectrum. In addition, we examine the dependence of the cross section on the center-of-mass energy for several benchmark scenarios in the allowed parameter space. These predictions can be probed at future high-energy $e^+e^-$ colliders, providing a sensitive test of the scotogenic framework and the role of fermionic dark matter, as well as enabling more stringent constraints on the model parameters.

Figures (6)

• Figure 1: Region in magenta color is allowed by $\mu\to e\gamma$ constraint for the parameters $M_2=M_1$, $M_3=M_1+380$ GeV, $m_H = M_1 +400$ GeV, $Y_2= 0.49$ and $Y_3 = 0.66$.
• Figure 2: Allowed regions after imposing $\frac{|\Delta m^2_{31}|}{\Delta m^2_{21}}$ constraints for the choice of the parameters as $M_2=M_1$, $M_3=M_1+380$ GeV, $m_0 = M_1 +750$ GeV, $Y_2= 0.49$ and $Y_3 = 0.66$.
• Figure 3: Allowed regions in the $M_1-Y_1$ plane by $\Omega \hat{h}^2$ constraints for the parameters $M_2=M_1$, $M_3=M_1+380$ GeV, $m_H = M_1 +400$ GeV, $m_0 = M_1 +750$ GeV, $Y_2= 0.49$ and $Y_3 = 0.66$.
• Figure 4: Allowed regions in the $M_1-Y_1$ plane by $\mu\to e\gamma$, $\frac{|\Delta m^2_{31}|}{\Delta m^2_{21}}$, $\Omega \hat{h}^2$ constraints $M_2=M_1$, $M_3=M_1+380$ GeV, $m_H = M_1 +400$ GeV, $m_0 = M_1 +750$ GeV, $Y_2= 0.49$ and $Y_3 = 0.66$.
• Figure 5: Z, photon and new singlet fermions $N_{1,2,3}$ individual contributions to the cross section of $\sigma_{e^+ e^-\to H^+ H^-}$ in red, orange and magenta colors respectively. The plots correspond to the allowed parameters $M_1=1005$ GeV, $M_2\simeq M_1=1005.0000035$ GeV, $M_3=1385$ GeV, $m_H = 1405$ GeV, $Y_1= 0.4258$, $Y_2= 0.49$ and $Y_3 = 0.66$.