Observable Signatures of Scotogenic Dirac Model

TL;DR

This paper explores the phenomenology of the scotogenic Dirac model, focusing on neutrino mass, dark matter, and experimental constraints from LFV, direct detection, and collider searches, highlighting the model's testability.

Contribution

It provides a comprehensive analysis of the scotogenic Dirac model's phenomenology, including constraints from LFV, dark matter relic density, direct detection, and collider signals, which was not thoroughly studied before.

Findings

LFV processes impose severe constraints on Yukawa couplings and masses.

Dark matter relic density can be achieved via annihilation through Yukawa y_χ.

Current direct detection bounds are loose but future experiments can improve constraints.

Abstract

In this work, we make a detailed discussion on the phenomenology of the scotogenic Dirac model, which could accommodate the Dirac neutrino mass and dark matter. We have studied the LFV processes in this model, which are mediated by the charged scalar $\phi^\pm$ and heavy fermions $N_i$. The experimental bounds, especially given by decays $\mu\to e\gamma$ and $\mu\to 3e$, have put severe constraints on Yukawa $y_\Phi$ and masses $m_{N1}$, $m_\phi$. We select the heavy fermion $N_1$ as dark matter candidate and find the correct relic density is basically by annihilating through another Yukawa $y_\chi$. After satisfying LFV and dark matter relic density constraints, we consider the indirect detections of dark matter annihilating into leptons. But the constraints are relatively loose. Then we make a detailed discussion on the dark matter direct detections. Although two Yukawa can both contribute to the direct detection processes, more attention has been paid on the $y_\Phi$-related processes as the $y_\chi$-related process is bounded loosely. The current and future direct detection experiments have been used to set constraints on the Yukawas and masses. The current direct detections bounds are relatively loose and can barely exclude more parameter region beyond the LFV. For the future direct detection experiments, the excluding capacities can be improved due to larger exposures. The detecting capabilities in the large mass region have not been weakened as the existence of mass enhancement from the magnetic dipole operator $\mathcal{O}_{\rm mag.}$. At last, we briefly discuss the collider signal searching in this model, the most promising signature is pair produced $\phi^+\phi^-$ and decay into signal of $\ell^+\ell^-+\not{\!\!E}_T$. The exclusion limits from collider on $m_{N1}$ and $m_\phi$ have provided a complementary detecting capability compared to the LFV and dark matter detections.