A complete analysis of FCNC and CP constraints in general SUSY extensions of the standard model

TL;DR

This work provides a comprehensive, model-independent analysis of FCNC and CP-violating constraints in general SUSY extensions using the mass insertion approximation. By parameterizing gluino- and photino-mediated effects with dimensionless insertions $\delta = \Delta / \tilde m^2$ across all chirality structures, the authors derive ΔF=2 and ΔF=1 bounds, including QCD-corrected Wilson coefficients and hadronic matrix elements, and apply them to SUSY-GUTs and non-universal soft-breaking scenarios. They show how constraints from $\Delta m_K$, $\varepsilon$, $\varepsilon'/\varepsilon$, $b\to s\gamma$, and lepton-flavor-violating decays tightly restrict the allowed flavor structure, and they caution that naive mass-insertion implementations can misestimate results in GUTs. The paper highlights the potential for SUSY to leave detectable indirect signatures in flavor and CP observables, especially in lepton-sector transitions like $\mu \to e \gamma$ and in kaon CP violation, thereby motivating careful, regime-aware phenomenology of SUSY models. Overall, the mass-insertion framework provides a practical, cross-model test of SUSY flavor physics with direct relevance to current and future experimental probes.

Abstract

We analyze the full set of constraints on gluino- and photino-mediated SUSY contributions to FCNC and CP violating phenomena. We use the mass insertion method, hence providing a model-independent parameterization which can be readily applied in testing extensions of the MSSM. In addition to clarifying controversial points in the literature, we provide a more exhaustive analysis of the CP constraints, in particular concerning $\varepsilon^\prime/\varepsilon$. As physically meaningful applications of our analysis, we study the implications in SUSY-GUT's and effective supergravities with flavour non-universality. This allows us to detail the domain of applicability and the correct procedure of implementation of the FC mass insertion approach.

Figures (13)

• Figure 1: Feynman diagrams for $\Delta S=2$ transitions, with $h,k,l,m=\{L,R\}$.
• Figure 2: The $\sqrt{\left|\mathop{\hbox{Re}} \left(\delta^{d}_{12} \right)_{LL}^{2}\right|}$ as a function of $x=m_{\tilde{g}}^2/m_{\tilde{q}}^2$, for an average squark mass $m_{\tilde{q}}=100\hbox{GeV}$.
• Figure 3: The $\sqrt{\left|\mathop{\hbox{Re}} \left(\delta^{d}_{12} \right)_{LR}^{2}\right|}$ as a function of $x=m_{\tilde{g}}^2/m_{\tilde{q}}^2$, for an average squark mass $m_{\tilde{q}}=100\hbox{GeV}$.
• Figure 4: The $\sqrt{\left|\mathop{\hbox{Re}} \left(\delta^{d}_{12} \right)_{LL} \left(\delta^{d}_{12} \right)_{RR}\right|}$ as a function of $x=m_{\tilde{g}}^2/m_{\tilde{q}}^2$, for an average squark mass $m_{\tilde{q}}=100\hbox{GeV}$.
• Figure 5: Box diagrams for $\Delta S=1$ transitions, with $h,k,m=\{L,R\}$.