Effect of an RRRR dimension 5 operator on the proton decay in the minimal SU(5) SUGRA GUT model

We reanalyze the proton decay in the minimal SU(5) SUGRA GUT model. Unlike previous analyses, we take into account a Higgsino dressing diagram of dimension 5 operator with right-handed matter fields (RRRR operator). It is shown that this diagram gives a dominant contribution for p → Kντ over that from LLLL operator, and decay rate of this mode can be comparable with that of p → Kνμ which is dominated by the LLLL contribution. It is found that we cannot reduce both the decay rate of p → Kντ and that of p → Kνμ simultaneously by adjusting relative phases between Yukawa couplings at colored Higgs interactions. Constraints on the colored Higgs mass MC and a typical squark and slepton mass mf̃ from Super-Kamiokande limit become considerably stronger due to the Higgsino dressing diagram of the RRRR operator: MC > 6.5× 10 GeV for mf̃ < 1 TeV, and mf̃ > 2.5 TeV for MC < 2.5× 10 GeV.