Radiative Corrections from Lattice QCD: Connecting Precision Measurements to Tests of the Standard Model

by Xin-Yu Tuo (Brookhaven national laboratory)

Tuesday 17 Nov 2026, 15:30 → 16:30 US/Eastern

Large Seminar Room

 

As precision tests of the Standard Model, such as CKM unitarity and lepton flavor universality, enter the sub-percent era, radiative corrections become indispensable for identifying small deviations that could signal new physics. Predicting them is highly challenging, as they intertwine long-distance QED with nonperturbative QCD and therefore require lattice QCD+QED calculations with controlled finite-volume systematics.

 

I will present an approach that treats the photon in infinite volume, strongly suppressing the finite-volume effects that have limited previous calculations. For first-row CKM unitarity, where current data show a tension with the Standard Model, we turn the isospin-breaking correction to kaon and pion leptonic decays from a leading into a subleading source of uncertainty. For lepton flavor universality, which the PIONEER experiment aims to test to 0.01% through the pion decay ratio $R_{e/\mu}$, we present the first lattice calculation of the hadronic-structure correction, giving a first-principles prediction of matching precision. In radiative leptonic decays, we find that higher-order corrections, enhanced by large collinear logarithms, reach 10% and explain significant discrepancies between theory and experiment, with direct implications for the ongoing NA62 measurement. Finally, I will discuss ongoing extensions of the method beyond leptonic decays and the opportunities they open for future precision tests of the Standard Model.