Neutron decay into a Dark Sector via Leptoquarks

Abstract: In this paper, we extend the Standard Model (SM) scalar sector with scalar leptoquarks (LQ) as a portal to the dark sector to resolve some observational anomalies simultaneously. We introduce LQ coupling to scalar dark matter (DM) to suggest an exotic decay channel for the neutron into scalar DM and an SM anti-neutrino. If the branching ratio of this new neutron decay channel is $1\%$, a long-standing discrepancy in the measured neutron lifetime between two different experimental methods, bottle and beam experiments, can be solved. The mass of the scalar DM produced from neutron decay should be in a narrow range and as a result, its production in the early universe is challenging. We discuss that the freeze-in mechanism can produce this scalar DM in the early universe with the correct relic abundance. Then we show that the model can explain other SM anomalies like the muon $(g-2)$, and $R_{D^{(*)}}$ anomaly simultaneously.