Lepton flavor violating decays of Higgs boson in the NB-LSSM

TL;DR

This work investigates lepton flavor violating Higgs decays in the NB-LSSM, a MSSM extension with local $U(1)_{B-L}$ symmetry and additional Higgs singlets. It employs both mass-eigenstate calculations and the mass-insertion approximation (MIA) to derive LFV amplitudes for $l_j\rightarrow l_i\gamma$ and $h\rightarrow l_i l_j$, highlighting the role of off-diagonal slepton mass insertions $\Delta^{XX}_{ij}$. The study performs a broad parameter scan under Higgs mass, signal strengths, and LFV constraints, revealing that BR$(h\rightarrow e\mu)$ is strongly suppressed (up to $\mathcal{O}(10^{-14})$) by $\mu\rightarrow e\gamma$, while BR$(h\rightarrow e\tau)$ and BR$(h\rightarrow \mu\tau)$ can reach $\mathcal{O}(10^{-6})$ with relevant slepton mixings $\delta^{XX}_{13,23}$ and moderately large $\tan\beta'$. The results show NB-LSSM offers detectable LFV signals in certain channels while remaining consistent with current data, underscoring the model’s potential as a window into new physics. These findings emphasize the importance of slepton flavor structure and extended Higgs sectors in shaping LFV phenomena at colliders.

Abstract

Lepton flavor violation (LFV) represents a clear new physics (NP) signal beyond the standard model (SM). NB-LSSM, the next to minimal supersymmetric extension of the SM with local B-L gauge symmetry, includes three Higgs singlets and three generations of right-handed neutrinos in the basis of MSSM, motivated by the new definition of SM-like Higgs resultly from the introducing of three Higgs singlets which mix with the two Higgs doublets at the tree level in the NB-LSSM. We calculate LFV processes $h\rightarrow l_i l_j$ in the mass eigenstate basis and the electroweak interaction basis separately, and the latter adopts the mass insertion approximation (MIA) method. In the suitable parameter space, we obtain the reasonable numerical results. At the same time, the corresponding constraints from the LFV rare decays $l_j\rightarrow l_iγ$ are considered to analyze the numerical results.

Figures (11)

• Figure 1: The triangle type diagrams for decays $l_j\rightarrow l_i \gamma$.
• Figure 2: The triangle and self-energy type diagrams for decays $h\rightarrow l_i\bar{l}_j$.
• Figure 3: The triangle type diagrams for decays $h\rightarrow l_i\bar{l}_j$ in the electroweak interaction basis.
• Figure 4: The self-energy type diagrams for decays $h\rightarrow l_i\bar{l}_j$ in the electroweak interaction basis.
• Figure 5: The scatter points for Higgs mass and signal strengths. The red star represents the best-fit point ($\chi^2_{\mathrm{best}} = 3.480$). All scattered points satisfy the $3\sigma$ experimental constraints of Higgs mass and the $2\sigma$ experimental constraints of corresponding Higgs decays.