Beyond oblique contributions: Δr and W-mass in models with scalar leptoquarks

Abstract

In this paper, we study the dominant nonuniversal contributions to muon decay for the five scalar leptoquarks (LQs) allowed by the Standard Model gauge symmetries. By using a common computational framework, we isolate the New-Physics (NP) one-loop corrections over the observable $\mathrm{\Delta }r$ and explore the connection with the W boson mass. We highlight the role of nonuniversal terms considering, for the $\mathrm{\text{SU}}(2)$ doublet and triplet LQs, a completely degenerate scenario, thus cancelling/moderating the effects of the oblique parameters S, T and U. We determine simple formulas that exhibit the leading nonuniversal behavior generated by the introduction of extra Yukawa terms and confront them against a present tension in $M_W$ and the projected FCC-ee accuracy.