用蒸馏法研究rho和a1介子在晶格上的衰变
Decay of rho and a1 mesons on the lattice using distillation
摘要：
我们提取的P波π-π相移的五个值的π介子相对动量，这给出了信息的ρ共振。Breit-Wigner公式很好地描述了π-π相移的依赖关系，我们在mpi=266 MeV处提取了m（rho）=792（7）（8）MeV和耦合g_{ρππ} =5.13（20）。我们从具有最小π介子相对动量的态中提取出P波散射长度a_{l=1} ^{ππ}=0.082（10）（3）fm^3。我们还确定了两个相对动量值的S波rho-pi相移，这提供了最低轴向共振a1（1260）的参数。使用Breit-Wigner拟合，我们提取出m（a1）=1.44（4）GeV和耦合g_{a_1ρπ} =1.1（3）GeV。从最低的状态，我们还提取rho-pi散射长度a_{l=0} ^{ρπ}=0.23（12）fm为我们的mpi。模拟使用一个Nf=2的规范配置与三叶草改进的威尔逊夸克系综。相移是由最低两个能级确定的，这是通过变分分析得到的夸克-反夸克和介子-介子插值。关联函数的计算采用了夸克的Laplacian Heaviside（LapH）涂抹的蒸馏方法。
英文摘要：
We extract the P-wave pi-pi phase shift for five values of pion relative momenta, which gives information on the rho resonance. The Breit-Wigner formula describes the pi-pi phase shift dependence nicely and we extract m(rho)=792(7)(8) MeV and the coupling g_{ρππ}=5.13(20) at our mpi=266 MeV. We extract the P-wave scattering length a_{l=1}^{ππ}=0.082(10)(3) fm^3 from the state with the lowest pion relative momenta. We also determine the S-wave rho-pi phase shift for two values of relative momenta, which provides parameters of the lowest axial resonance a1(1260). Using the Breit-Wigner fit we extract m(a1)=1.44(4) GeV and the coupling g_{a_1ρπ}=1.1(3) GeV. From the lowest state we also extract the rho-pi scattering length a_{l=0}^{ρπ}=0.23(12) fm for our mpi. The simulation is performed using one Nf=2 ensemble of gauge configurations with clover-improved Wilson quarks. The phase shifts are determined from the lowest two energy-levels, which are obtained by the variational analysis with a number of quark-antiquark and meson-meson interpolators. The correlation functions are calculated using the distillation method with the Laplacian Heaviside (LapH) smearing of quarks.
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