School of Mathematics, Trinity College, Dublin 2, Ireland.
Thomas Jefferson National Accelerator Facility, 12000 Jefferson Avenue, Newport News, Virginia 23606, USA.
Phys Rev Lett. 2019 Jul 26;123(4):042002. doi: 10.1103/PhysRevLett.123.042002.
We present a determination of the isospin-1/2 elastic πK scattering amplitudes in S and P partial waves using lattice quantum chromodynamics. The amplitudes, constrained for a large number of real-valued energy points, are obtained as a function of light-quark mass, corresponding to four pion masses between 200 and 400 MeV, at a single lattice spacing. Below the first inelastic threshold, the P-wave scattering amplitude is dominated by a single pole singularity that evolves from being a stable bound state at the highest quark mass into a narrow resonance that broadens as the pion and kaon masses are reduced. As in experiment, the S-wave amplitude does not exhibit an obviously resonant behavior, but instead shows a slow rise from threshold, which is not inconsistent with the presence of a κ/K_{0}^{⋆}(700)-like resonance at the considered quark masses. As has been found in analyses of experimental scattering data, simple analytic continuations into the complex energy plane of precisely determined lattice QCD amplitudes on the real energy axis are not sufficient to model-independently determine the existence and properties of this state. The spectra and amplitudes we present will serve as an input for increasingly elaborate amplitude analysis techniques that implement more of the analytic structure expected at complex energies.
我们利用格点量子色动力学（lattice quantum chromodynamics）确定了同位旋 1/2 弹性 πK 散射振幅在 S 和 P 分波中的情况。这些振幅是在单个格点间距下，在大量实能点的约束下，作为轻夸克质量的函数得出的，对应于 200 到 400 MeV 之间的四个介子质量。在第一个非弹性阈之下，P 波散射振幅主要由一个单极点奇点主导，该奇点从最高夸克质量处的稳定束缚态演化成一个狭窄的共振，随着介子和 K介子质量的降低而变宽。与实验一样，S 波振幅没有表现出明显的共振行为，而是从阈缓慢上升，这与在考虑的夸克质量处存在κ/K_{0}^{⋆}(700)-样的共振并不矛盾。正如在对实验散射数据的分析中发现的那样，简单地将精确确定的格点 QCD 振幅在实能轴上的解析延拓到复能平面中，不足以独立于模型地确定该状态的存在和性质。我们呈现的谱和振幅将作为输入，用于越来越精细的振幅分析技术，这些技术将实现对复杂能下预期的更多解析结构的实现。
