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, ${\Lambda }_{\mathrm{pre}}$. Our estimate of the limit imposed by searches for proton decays is ${\Lambda }_{\mathrm{pre}}>10^4{\mathrm{TeV}}^{1/2}{C}_8^{1/4}{m}_{\mathcal{Q}}^{1/2}$, where $C_8$ 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 $C_8$ in the $10^{-5}-1$ range, the lower limit on ${\Lambda }_{\mathrm{pre}}$ varies between $3\times 10^3$ TeV and $5\times 10^4$ TeV. We point out that exotic proton decay modes, into a ${\pi }^{+}$ and a heavy right-handed neutrino, could be observed using the Super-Kamiokande or DUNE detectors.

Comments: 24 pages, 5 figures