Proton decay from quark and lepton compositeness

Abstract

Within a chiral SU(15) gauge theory in which the Standard Model fermions are bound states of massless preons, we show that proton-decay operators are likely induced at the compositeness scale, Λpre. Our estimate of the limit imposed by searches for proton decays is Λpre> 104 TeV1/2 {C}_8^{1/4} {m}_{mathcal{Q}}^{1/2} , where C8 is a rescaled coefficient of an 8-prebaryon operator induced by SU(15) dynamics, and {m}_{mathcal{Q}} is the mass of a composite vectorlike quark. The latter has a lower limit related to the mass of a composite vectorlike lepton, which in turn is required by LHC searches to be above 1 TeV. For C8 in the 10−5 – 1 range, the lower limit on Λpre varies between 3 × 103 TeV and 5 × 104 TeV. We point out that exotic proton decay modes, into a π+ and a heavy right-handed neutrino, could be observed using the Super-Kamiokande or DUNE detectors.