Work

Kaon radiative leptonic decay rates from lattice QCD simulations at the physical point

Year: 2025

Type: article

Abstract: We present a lattice quantum chromodynamics (QCD) calculation of the radiative leptonic decay rates of the kaon, improving upon our previous work in Desiderio [First lattice calculation of radiative leptonic decay rates of pseudoscalar mesons, ]. Our analysis uses gauge ensembles generated by the Extended Twisted Mass Collaboration (ETMC) with N f = 2 + 1 + 1 flavors of Wilson-clover twisted mass fermions. For the first time, we go beyond the electroquenched approximation by including quark-disconnected contributions. Several key improvements have been implemented: (i) the simulations are now performed directly at physical light- and strange-quark masses, (ii) finite-size effects are carefully investigated using lattices with spatial extents ranging from L ≃ 3.8 fm to L ≃ 7.7 fm , and (iii) the continuum extrapolation is based on three lattice spacings in the range a ∈ [ 0.08 , 0.058 ] fm . As a result of the high-precision determination of the relevant correlation functions, we reduce the uncertainties on both the axial and vector form factors by nearly a factor of two compared to our previous analysis. When compared to experimental measurements in the electron channel ( K − → e − ν ¯ e γ ), our results show a tension—at the level of 2.6 standard deviations—with respect to KLOE data. On the other hand, they are compatible with measurements from the E36 Collaboration at J-PARC. In the muonic decay channel ( K − → μ − ν ¯ μ γ ), we confirm the tensions, already observed in our previous study, between lattice QCD predictions and ISTRA + and OKA data, which are both primarily sensitive to the value of the negative-helicity form factor F − .

Source: Physical review. D/Physical review. D.

DOI: 10.1103/r55k-cnqg