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

Preprint number: CP3-Origins-2018-5 DNRF90
Authors: Ruairi Brett (Carnegie Mellon), John Bulava (CP3-Origins & DIAS), Jacob Fallica (U. of Kentucky), Andrew Hanlon (U. of Mainz), Ben Hoerz (U. of Mainz), and Colin Morningstar (Carnegie Mellon)
The elastic $$I=1/2$$, $$s$$- and $$p$$-wave kaon-pion scattering amplitudes are calculated using a single ensemble of anisotropic lattice QCD gauge field configurations with $$N_{\mathrm{f}} = 2+1$$ flavors of dynamical Wilson-clover fermions at $$m_{\pi} = 230\mathrm{MeV}$$. A large spatial extent of $$L = 3.7\mathrm{fm}$$ 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 $$m_{K^{*}}/m_{\pi} = 3.808(18)$$ and $$g^{\mathrm{BW}}_{K^{*}K\pi} = 5.33(20)$$ 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 $$m_{\pi}a_0 = -0.353(25)$$.