Probing low energy scalar leptoquarks by the leptonic W and Z couplings

Abstract We compute the generic one-loop contribution involving scalar leptoquarks (LQ) to the W and Z leptonic decay widths. In our computation we include for the first time the finite terms and the corrections due to the external momenta of the electroweak bosons, which is a step beyond the leading-logarithmic approximation considered in the literature so far. We show that the terms we include can be numerically quite significant. They amount to about 20% for scalar LQ masses below 1.5 TeV, as currently allowed by the direct searches at the LHC. To further illustrate the relevance of our results we revisit a model with two light scalar LQs, proposed to accommodate the B-physics anomalies. We show that the finite terms we computed can reduce the tension with the Z-pole data