修正的轮廓-改进的摄动理论
Modified Contour-Improved Perturbation Theory
摘要：
半强子τ衰变宽度允许在低能量下干净地提取强耦合常数。我们提出了一种修改的标准的“轮廓改进”的方法的基础上衍生扩展的阿德勒功能。该方法消除了歧义来自不同的积分表达式的存在的半强子τ衰变比。与标准方法相比，修正围道改进微扰理论的重正化尺度依赖性弱了两倍多。膨胀的最后一项减少了，重整化方案的依赖性保持近似相等。提取的QCD耦合在tau质量尺度是由2 $%$低于“轮廓改善”的值。我们找到了$α_s(M_Z^2)=0.1211\pm 0.0010$。
英文摘要：
The semihadronic tau decay width allows a clean extraction of the strong coupling constant at low energies. We present a modification of the standard "contour improved" method based on a derivative expansion of the Adler function. The approach eliminates ambiguities coming from the existence of different integral expressions for the semihadronic tau decay ratio. Compared to the standard method, renormalization scale dependence is by more than a factor two weaker in modified contour improved perturbation theory. The last term of the expansion is reduced, and renormalization scheme dependence remains approximately equal. The extracted QCD coupling at the tau mass scale is by 2$%$ lower than the "contour improved" value. We find $α_s(M_Z^2)=0.1211\pm 0.0010$.
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