Determination of s- and p-wave I = 1/2 Kπ scattering amplitudes in Nf = 2 + 1 lattice QCD

Abstract

The elastic I = 1/2, sand p-wave kaon-pion scattering amplitudes are calculated using a single ensemble of anisotropic lattice QCD gauge field configurations with N f = 2 + 1 flavors of dynamical Wilsonclover fermions at m = 230 MeV. A large spatial extent of L = 3.7 fm enables a good energy resolution while partial wave mixing due to the reduced symmetries of the finite volume is treated explicitly. The p-wave amplitude is well described by a Breit-Wigner shape with parameters m K * /m = 3.808(18) and g BW K * K = 5.33(20) which are insensitive to the inclusion of d-wave mixing and variation of the s-wave parametrization. An effective range description of the near-threshold s-wave amplitude yields m a 0 = -0.353(25).