Analysis of K+ → e + νeγ in light-front quark model and chiral perturbation theory of order p6

Within the frameworks of the light-front quark model(LFQM) and chiral perturbation theory(ChPT) of O(p⁶), we reevaluate the form factors of the K⁺→γ transition. We use these form factors to study the decay of K⁺→e⁺ν_eγ, which is dominated by the structure-dependent  contribution. We show the differential decay branching ratio as a function of x=2E_γ/m_K, where E_γ(m_K) is the photon energy(kaon mass). Explicitly, we find that, in the standard model with the cut of x=0.01(0.1), the decay branching ratio of K⁺→e⁺ν_eγ is 1.54(1.44)×10⁻⁵ and 1.57(1.47)×10⁻⁵ in the LFQM and ChPT, respectively.