Hide and Seek with Massive Fields in Modulus Mediation

We study the modulus mediation of supersymmetry breaking motivated by superstring theory. We show that the renormalization group running of the soft supersymmetry breaking parameters due to the interactions of massive fields is canceled by the threshold corrections at one-loop order, if their mass is given by nonperturbative dynamics controlled by the same modulus that mediates supersymmetry breaking and a sum rule of the modular weights holds for the Yukawa couplings. As an example, we discuss order reduction of lepton flavor violation in the supersymmetric seesaw mechanism, which revives the parameter space already excluded.

Figure 1

$\mathrm{BR}(\mu \to e\gamma )$ in the MSSM with right-handed neutrinos. The solid (dashed) curve represents the result for the nonperturbative (constant) mass term. The gluino mass is 2.3 TeV at the one-loop level.

Figure 2

The same as in Fig. 1 except the sum rule is violated in the neutrino Yukawa coupling ($c_{\overline{N}=0}$).