Speaker
Description
We investigate a class of baryogenesis scenarios in which the Standard Model is extended by heavy right-handed neutrinos (RHNs) and a scalar leptoquark. The out-of-equilibrium, CP-violating decays of the RHNs into quarks and leptoquarks generate a net $B-L$ asymmetry, which is subsequently converted into a baryon asymmetry through electroweak sphaleron processes. Unlike standard type-I seesaw leptogenesis, the CP-asymmetry parameter $\epsilon$ is not directly bounded by the light-neutrino masses. Consequently, the Davidson–Ibarra bound can be evaded, allowing successful baryogenesis for RHN masses well below $10^9~{\rm GeV}$. We illustrate this mechanism using the scalar leptoquark $\bar S_1\sim(3,1,-2/3)$, which admits the diquark interaction $\bar S_1\,\overline{d_R^C}d_R$. In combination with the leptoquark–RHN coupling and active–sterile neutrino mixing, this interaction induces proton decay. We calculate the relevant proton-decay rates and branching fractions and derive constraints on the diquark couplings. Finally, we examine the complementary constraints arising from Big Bang nucleosynthesis, ATLAS searches for long-lived $R$-hadrons, and the sensitivity of Super-Kamiokande proton-decay searches.