Precision for B-meson matrix elements - High Energy Physics - LatticeReport as inadecuate

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Abstract: We demonstrate how HQET and the Step Scaling Method for B-physics, pioneeredby the Tor Vergata group, can be combined to reach a further improvedprecision. The observables considered are the mass of the b-quark and theB s-meson decay constant. The demonstration is carried out in quenched latticeQCD. We start from a small volume, where one can use a standard Oa-improvedrelativistic action for the b-quark, and compute two step scaling functionswhich relate the observables to the large volume ones. In all steps weextrapolate to the continuum limit, separately in HQET and in QCD for massesbelow m b. The physical point m b is then reached by an interpolation of thecontinuum results in 1-m. The essential, expected and verified, feature is thatthe step scaling fuctions have a weak mass-dependence resulting in an easyinterpolation to the physical point. With r 0=0.5fm and the experimental B sand K masses as input, we find F Bs=1916MeV and the renormalization groupinvariant mass M b=6.8810GeV, translating into m bm b=4.426GeV in theMSbar scheme. This approach seems very promising for full QCD.

Author: Damiano Guazzini, Rainer Sommer, Nazario Tantalo


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