Electroweak Corrections to the Charm Quark Contribution to K+ -> pi+ nu nu-bar

TL;DR

This paper calculates electroweak and QED corrections to the charm quark's role in the rare decay K+ -> pi+ nu nu-bar, refining theoretical predictions for its branching ratio.

Contribution

It provides the first comprehensive calculation of electroweak and QED corrections to the charm contribution in this decay process, improving accuracy over previous QCD-only estimates.

Findings

P_c(X) increased by up to 2% due to corrections

Branching ratio B(K+ -> pi+ nu nu-bar) estimated at (8.5 +- 0.7) x 10^{-11}

Theoretical uncertainties are dominated by CKM parameters.

Abstract

We compute the leading-log QED, the next-to-leading-log QED-QCD, and the electroweak corrections to the charm quark contribution relevant for the rare decay K+ -> pi+ nu nu-bar. The corresponding parameter P_c(X) is increased by up to 2% with respect to the pure QCD estimate to P_c(X) = 0.372 +- 0.015 for m_c(m_c)= (1.286 +- 0.013) GeV, alphas(M_Z) = 0.1176 +- 0.0020 and |V_us| = 0.2255. For the branching ratio we find B(K+ -> pi+ nu nu-bar) = (8.5 +- 0.7)*10^{-11}, where the quoted uncertainty is dominated by the CKM elements.