Flavor in Supersymmetry with an Extended R-symmetry

TL;DR

The paper introduces the MRSSM, which enforces an extended R-symmetry to forbid Majorana gaugino masses, the mu-term, and A-terms, replacing the MSSM with a model featuring Dirac gauginos and an extended Higgs sector. This framework allows order-one flavor-violating soft masses in the squark and slepton sectors while keeping EDMs and εK within experimental bounds, thanks to the Dirac structure and absence of left-right mixing. At large tanβ, the modified Higgs sector prevents the usual tanβ-enhanced FCNCs, and CP-violating constraints can be satisfied with either CP-conserving SUSY breaking or moderate flavor degeneracy. The paper also discusses potential UV completions and distinctive phenomenology, including novel collider signatures and avenues for unification, establishing MRSSM as a viable alternative to flavor-blind mediation in SUSY models.

Abstract

We propose a new solution to the supersymmetric flavor problem without flavor-blind mediation. Our proposal is to enforce a continuous or a suitably large discrete R-symmetry on weak scale supersymmetry, so that Majorana gaugino masses, trilinear A-terms, and the mu-term are forbidden. We find that replacing the MSSM with an R-symmetric supersymmetric model allows order one flavor-violating soft masses, even for squarks of order a few hundred GeV. The minimal R-symmetric supersymmetric model contains Dirac gaugino masses and R-symmetric Higgsino masses with no left-right mixing in the squark or slepton sector. Dirac gaugino masses of order a few TeV with vanishing A-terms solve most flavor problems, while the R-symmetric Higgs sector becomes important at large tan(beta). epsilon_K can be accommodated if CP is preserved in the SUSY breaking sector, or if there is a moderate flavor degeneracy, which can arise naturally. epsilon'/epsilon, as well as neutron and electron EDMs are easily within experimental bounds. The most striking phenomenological distinction of this model is the order one flavor violation in the squark and slepton sector, while the Dirac gaugino masses tend to be significantly heavier than the corresponding squark and slepton masses.

Figures (10)

• Figure 1: Box diagram contributing to $K-\bar{K}$ mixing.
• Figure 2: Contours of $\delta$ where $\Delta M_{\rm box} = \Delta M_k$ for a) $\delta_{LL}=\delta$, $\delta_{RR}=0$, b) $\delta_{LL}=\delta_{RR}=\delta$. An identical plot to a) exists for $\delta_{LL}=0$, $\delta_{RR} =\delta$. Contours are $\delta =0.03,0.1,0.3,1$ for dotted, dot-dashed, solid, dashed respectively.
• Figure 3: Same as Fig. \ref{['fig:kkbarlimits']} but for $B_d$ mesons. Contours of $\delta$ where $\Delta M_{\rm box} = \Delta M_{B_d}$ for a) $\delta_{LL}=\delta$, $\delta_{RR}=0$, b) $\delta_{LL}=\delta_{RR}=\delta$. An identical plot to a) exists for $\delta_{LL}=0$, $\delta_{RR} =\delta$. Contours are $\delta =0.1,0.3,1$ for dot-dashed, solid, dashed respectively.
• Figure 4: Internal (Yukawa) chirality flip diagram contributing to $\mu \rightarrow e \gamma$; $\chi_d$, $\lambda$ denote the appropriate Dirac Higgsino and gaugino and the photon here and in Fig. \ref{['fig:LFVexternal']} can be attached to any charged line.
• Figure 5: External chirality flip diagram contributing to $\mu \rightarrow e\gamma$; $\lambda$ denotes the appropriate Dirac gaugino.