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Lepton Flavor Violation of Z Gauge Boson Decays in Supersymmetric Type-III Seesaw Model

Vael Hajahmad, Murhaf Alsayed Ali

Abstract

In this study, we investigate the lepton flavor violation (LFV) of Z gauge boson decaying into two different flavor charged leptons $Z\rightarrow l_i l_j$ ($Z\rightarrow τμ$, $Z\rightarrow τe$ and $Z\rightarrow μe$). This work is performed in the framework of the constrained minimal supersymmetric standard model (CMSSM) which is extended by the type-III seesaw mechanism. By considering constraints from the current experimental bounds on neutrino and supersymmetric particle masses, we calculate the branching ratios of the LFV of $Z$ boson decays. The numerical results are found to be $1.30 \times {10}^{-9}$ for both the $τμ$ and $τe$ decay channels and $6.40 \times {10}^{-10}$ for the $μe$ channel. After applying the constraints from the experimental bounds on the radiative two body decays $l_{i}\rightarrow l_{j} γ$, the branching ratios of the LFV of $Z$ boson decays get an additional suppression of $10^{-3}$ for the $τμ$ and $τe$ decay channels and $10^{-8}$ for the $μe$ channel. Our prediction of the branching ratios is several orders of magnitude below the current experimental bounds.

Lepton Flavor Violation of Z Gauge Boson Decays in Supersymmetric Type-III Seesaw Model

Abstract

In this study, we investigate the lepton flavor violation (LFV) of Z gauge boson decaying into two different flavor charged leptons (, and ). This work is performed in the framework of the constrained minimal supersymmetric standard model (CMSSM) which is extended by the type-III seesaw mechanism. By considering constraints from the current experimental bounds on neutrino and supersymmetric particle masses, we calculate the branching ratios of the LFV of boson decays. The numerical results are found to be for both the and decay channels and for the channel. After applying the constraints from the experimental bounds on the radiative two body decays , the branching ratios of the LFV of boson decays get an additional suppression of for the and decay channels and for the channel. Our prediction of the branching ratios is several orders of magnitude below the current experimental bounds.

Paper Structure

This paper contains 14 sections, 50 equations, 9 figures, 8 tables.

Table of Contents

  1. Introduction
  2. MSSM-Seesaw Type-III model
  3. The structure of Yukawa matrix
  4. The $Z$ boson LFV decays ($Z\rightarrow l_{i} l_{j}$)
  5. Numerical Results and Discussion
  6. BR($Z\rightarrow l_{i} l_{j}$) without constraints from $(l_{i}\rightarrow l_{j} \gamma)$ decays
  7. BR($Z\rightarrow l_i l_j$) with constraints from $(l_{i}\rightarrow l_{j} \gamma)$ decays
  8. Conclusions
  9. Appendix: Vertexes
  10. Two Fermions - Z Boson Interactions:
  11. Two Scalars - Z Boson Interactions:
  12. Two Fermions - One Scalar Interactions:
  13. Two Scalars - $\gamma$ Interactions:
  14. Two Fermions - $\gamma$ Interactions:

Figures (9)

  • Figure 1: One loop Feynman diagrams contributing to BR$(Z\rightarrow l_i \bar{l_j})$ in the MSSM-Seesaw type-III model.
  • Figure 2: BR$(Z\rightarrow l_i l_j)$ as a function of cos($\theta_{ij}$) at $A_0=0,\ 1850$ GeV and tan$\beta$=5, 20. For all above plots we set $m_{1/2} =$$m_0 = 500$ GeV, $f=1$ and $M_W= 2.5\times{10}^{13}$ GeV.
  • Figure 3: BR$(Z\rightarrow l_i l_j)$ as a function of the strength of neutrino Yukawa coupling (f) at two values of $M_W = 2.5\times{10}^{13}$ GeV (left), and $2.5\times{10}^{14}$ GeV (right). The other input parameter are fixed as $m_0=m_{1/2}=500$ GeV, $A_0=1850$ GeV, tan$\beta$=20 and cos($\theta_{ij}$)=0.91.
  • Figure 4: BR$(Z\rightarrow l_i l_j)$ as a contour in the $m_0$ and $m_{1/2}$ plane. BR$(Z\rightarrow \tau \mu)$ shown in upper-left figure, BR$(Z\rightarrow\tau e)$ shown in upper-right one and BR$(Z\rightarrow \mu e)$ shown in bottom one. Other input parameters are fixed as follows: $A_0 = 1850$ GeV, tan$\beta = 20$, cos($\theta_{ij}$) = 0.91, $f$=0.85 and $M_W= 2.5\times{10}^{13}$ GeV.
  • Figure 5: One loop Feynman diagrams contributing to BR$(l_{i}\rightarrow l_{j} \gamma)$ in the MSSM-Seesaw type-III model.
  • ...and 4 more figures