Higgs-Mediated Electric Dipole Moments in the MSSM: An Application to Baryogenesis and Higgs Searches

TL;DR

This work analyzes Higgs‑mediated EDMs in the MSSM, showing that two‑loop Barr–Zee diagrams with third‑generation fermions/sfermions, charginos, and gluinos dominate EDM signals when the first two sfermion generations are heavy. It demonstrates strong correlations among CP‑violating operators, leading to cancellations that can suppress d_Tl and d_n within current bounds, while highlighting the muon EDM as a powerful complementary probe. The study updates CPX benchmark scenarios to reflect these EDM constraints and discusses implications for electroweak baryogenesis and Higgs searches at colliders. The results underscore the interplay between precision EDM measurements and collider tests in constraining radiatively generated CP violation in the Higgs sector of the MSSM.

Abstract

We perform a comprehensive study of the dominant two- and higher-loop contributions to the $^{205}$Tl, neutron and muon electric dipole moments induced by Higgs bosons, third-generation quarks and squarks, charginos and gluinos in the Minimal Supersymmetric Standard Model (MSSM). We find that strong correlations exist among the contributing CP-violating operators, for large stop, gluino and chargino phases, and for a wide range of values of $\tanβ$ and charged Higgs-boson masses, giving rise to large suppressions of the $^{205}$Tl and neutron electric dipole moments below their present experimental limits. Based on this observation, we discuss the constraints that the non-observation of electric dipole moments imposes on the radiatively-generated CP-violating Higgs sector and on the mechanism of electroweak baryogenesis in the MSSM. We improve previously suggested benchmark scenarios of maximal CP violation for analyzing direct searches of CP-violating MSSM Higgs bosons at high-energy colliders, and stress the important complementary rôle that a possible high-sensitivity measurement of the muon electric dipole moment to the level of $10^{-24}$ $e$ cm can play in such analyses.

Figures (9)

• Figure 1: Feynman graphs contributing to a non-vanishing CP-odd electron--nucleon operator $C_S$. At the elementary particle level, $C_S$ is predominantly induced by quantum effects involving (a) $t$-,$b$- quarks and (b) $\tilde{t}$-, $\tilde{b}$- squarks. Blobs and heavy dots denote resummation of self-energy and vertex graphs, respectively.
• Figure 2: Dominant Higgs-boson two-loop contributions to EDM of a light fermion $f = e,\mu,d$ in the MSSM with explicit CP violation (mirror-symmetric graphs are not displayed). Heavy dots indicate resummation of self-energy and vertex graphs. Two-loop graphs generating a CEDM for a $d$-quark are also shown.
• Figure 3: Numerical estimates of $^{205}$Tl EDM $d_{\rm Tl}$ induced by the CP-odd electron--nucleon operator $C_S$ as functions of $\tan\beta$, in four selected CPX scenarios with $M_{\rm SUSY} = 1$ TeV. The values of the CPX parameters are given in (\ref{['CPX']}). The individual $b,\tilde{t},t,\tilde{b}$ contributions to $d_{\rm Tl}(C_S)$, along with their relative signs, are also displayed.
• Figure 4: Numerical estimates of resummed Higgs-boson two-loop effects on $d_e$, induced by $t,b$- quarks and $\tilde{t},\tilde{b}$- squarks, as functions of $\tan\beta$, in two variants of the CPX scenario, with (a) $M_{H^+} = 150$ GeV and (b) $M_{H^+} = 300$ GeV. The long-dash-dotted lines indicate the stop/sbottom contributions to $d_e$. The dotted lines $t_{1,2,3}$ correspond to top/bottom contributions, for ${\rm arg} (m_{\tilde{g}} ) = 90^\circ,\ 0^\circ,\ -90^\circ$, respectively. Likewise, the solid lines $1,2,3$ give the sum of all the aforementioned contributions to $d_e$ for the same values of gluino phases. Contributions to $d_e$ that are denoted with a minus sign are negative.
• Figure 5: Numerical values of resummed Higgs-boson two-loop effects on $d_e$, induced by $t,b$- quarks and $\tilde{t},\tilde{b}$- squarks, as functions of $\mu$, in two variants of the CPX scenario, with $\tan\beta = 20$, and (a) $M_{H^+} = 150$ GeV and (b) $M_{H^+} = 300$ GeV. The meaning of the different line types is identical to that of Fig. \ref{['fig2']}. For $A_{t,b} = 0$, the long-dash-dotted line disappears and so the solid lines collapse to the dotted ones.