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Sfermion masses in Nelson-Strassler type of models: SUSY standard models coupled with SCFTs

Tatsuo Kobayashi, Haruhiko Terao

TL;DR

The paper analyzes soft SUSY breaking in Nelson–Strassler type models where SUSY Standard Models are coupled to SCFTs. By deriving exact beta functions and studying RG flows near IR fixed points, it shows that soft terms can be exponentially suppressed for fields with definite anomalous dimensions, promoting sfermion degeneracy. In realistic scenarios with SM gauge couplings, residual splittings remain of order $O(\alpha_a M_a^2)$, with degeneracy enhanced for squarks but less so for sleptons, and explicit models demonstrate convergence toward finite, flavor-dependent masses. Additionally, the work proposes a mechanism to generate the $\mu$-term via a singlet coupled to the SCFT and provides representative mass spectra and convergence behavior, highlighting implications for FCNC constraints and model-building viability.

Abstract

We study soft SUSY breaking parameters in the Nelson-Strassler type of models: SUSY standard models coupled with SCFTs. In this type of models, soft SUSY breaking parameters including sfermion masses can be suppressed around the decoupling scale of SCFTs. We clarify the condition to derive exponential suppression of sfermion masses within the framework of pure SCFTs. Such behavior is favorable for degeneracy of sfermion masses. However, the realistic sfermion masses are not quite degenerate due to the gauge couplings and the gaugino masses in the SM sector. We show the sfermion mass spectrum obtained in such models. The aspect of suppression for the soft SUSY breaking parameters is also demonstrated in an explicit model. We also give a mechanism generating the $μ$-term of the Electro-Weak scale by a singlet field coupled with the SCFT.

Sfermion masses in Nelson-Strassler type of models: SUSY standard models coupled with SCFTs

TL;DR

The paper analyzes soft SUSY breaking in Nelson–Strassler type models where SUSY Standard Models are coupled to SCFTs. By deriving exact beta functions and studying RG flows near IR fixed points, it shows that soft terms can be exponentially suppressed for fields with definite anomalous dimensions, promoting sfermion degeneracy. In realistic scenarios with SM gauge couplings, residual splittings remain of order , with degeneracy enhanced for squarks but less so for sleptons, and explicit models demonstrate convergence toward finite, flavor-dependent masses. Additionally, the work proposes a mechanism to generate the -term via a singlet coupled to the SCFT and provides representative mass spectra and convergence behavior, highlighting implications for FCNC constraints and model-building viability.

Abstract

We study soft SUSY breaking parameters in the Nelson-Strassler type of models: SUSY standard models coupled with SCFTs. In this type of models, soft SUSY breaking parameters including sfermion masses can be suppressed around the decoupling scale of SCFTs. We clarify the condition to derive exponential suppression of sfermion masses within the framework of pure SCFTs. Such behavior is favorable for degeneracy of sfermion masses. However, the realistic sfermion masses are not quite degenerate due to the gauge couplings and the gaugino masses in the SM sector. We show the sfermion mass spectrum obtained in such models. The aspect of suppression for the soft SUSY breaking parameters is also demonstrated in an explicit model. We also give a mechanism generating the -term of the Electro-Weak scale by a singlet field coupled with the SCFT.

Paper Structure

This paper contains 14 sections, 68 equations, 2 figures.

Table of Contents

  1. Introduction
  2. Exact results for soft masses in SCFT
  3. Beta functions
  4. RG flows around the IR stable fixed points
  5. Higher dimensional interactions
  6. SSMs coupled with SCFT
  7. Yukawa hierarchy
  8. Degeneracy of sfermion masses
  9. Mass spectrum
  10. Analyses of squark masses in explicit models
  11. Models with suppressed soft parameters
  12. Sfermion mass convergence in $SU(3)_{SC}\times SU(3)_C$ model
  13. Generation of $\mu$-term by a singlet
  14. Conclusions and discussions

Figures (2)

  • Figure 7: The running couplings $(y_1, M', A_{\lambda})$ are shown in ratio to their initial values by a solid, a dashed and a long-dashed line respectively. $t=\log_{10}(\mu/\Lambda_c)$.
  • Figure 8: RG flows for $(m^2_1, m^2_Q+m^2_P)$ shown by solid and dashed lines respectively. The long dashed line gives $\alpha M^2$.