Leptoquarks with exactly stable protons

We explore a novel mechanism to restrict TeV-scale leptoquark interactions and render the proton exactly
stable to all orders in the effective field theory expansion. A scalar condensate breaks a lepton-flavoured
U(1)X gauge symmetry in the ultraviolet and generates neutrino masses, leaving a discrete Z9 or Z18
gauge symmetry in the infrared, forbidding �B = 1 processes. This provides an elegant framework to
address the flavour anomalies and can be adapted to many other new-physics models. The U(1)X can
emerge from a gauge–flavour unified SU(12) × SU(2) × SU(2) theory at even higher energies.