DAMTP, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, United Kingdom.
Phys Rev Lett. 2013 May 31;110(22):222003. doi: 10.1103/PhysRevLett.110.222003.
We present the first lattice QCD calculation of the decay constants f(B) and f(B(s)) with physical light quark masses. We use configurations generated by the MILC Collaboration including the effect of u, d, s, and c highly improved staggered quarks in the sea at three lattice spacings and with three u/d quark mass values going down to the physical value. We use improved nonrelativistic QCD (NRQCD) for the valence b quarks. Our results are f(B)=0.186(4) GeV, f(B(s))=0.224(4) GeV, f(B(s))/f(B)=1.205(7), and M(B(s))-M(B)=85(2) MeV, superseding earlier results with NRQCD b quarks. We discuss the implications of our results for the standard model rates for B((s))→μ(+)μ(-) and B→τν.
我们提出了第一个晶格 QCD 计算，用物理轻夸克质量计算了衰变常数 f(B)和 f(B(s))。我们使用 MILC 合作组织生成的配置，包括海相中 u、d、s 和 c 高改进的交错夸克的影响，在三个晶格间距和三个 u/d 夸克质量值下降到物理值。我们使用改进的非相对论 QCD（NRQCD）来处理价 b 夸克。我们的结果是 f(B)=0.186(4)GeV，f(B(s))=0.224(4)GeV，f(B(s))/f(B)=1.205(7)，M(B(s))-M(B)=85(2)MeV，取代了以前用 NRQCD b 夸克得到的结果。我们讨论了我们的结果对标准模型 B((s))→μ(+)μ(-)和 B→τν 速率的影响。
