Nicola Valori: "Pion β decay and τ→π π ν_τ beyond leading logarithms"

Thursday 26 Mar 2026, 13:30 → 14:30 Europe/Rome

Sala Direzione

Semi-leptonic processes involving pions are used to test the Standard Model at high precision. On the theory side, the evaluation of radiative corrections is a crucial ingredient for a robust comparison between theoretical predictions and experimental measurements. In this talk, I will present the first complete effective field theory treatment of radiative corrections in pion $\beta$ decay ($\pi^{\pm} \rightarrow \pi^0 \, e \, \nu_{e}$) and $\tau^{\pm} \rightarrow  \pi^{\pm} \, \pi^{0} \, \nu_{\tau}$ beyond leading-logarithmic accuracy. As main applications, I will first show how the theoretical uncertainty for the SM prediction of $V_{ud}$ based on pion  $\beta$ decay is reduced by a factor of three, making it negligible even beyond the reach of the PIONEER experiment. Second, I will present an evaluation of isospin-breaking corrections to $\tau \rightarrow \pi \pi \nu_{\tau}$ with negligible uncertainty from the short-distance matching, as necessary for a future $\tau$-based determination of the hadronic-vacuum-polarization contribution to the anomalous magnetic moment of the muon.