Masses and decay constants of the B-system in Lattice QCD

TL;DR

This paper uses Lattice QCD to calculate properties of B-mesons and related particles, providing estimates for decay constants and masses relevant to experiments, with comparisons to other methods and experimental data.

Contribution

It presents new lattice QCD calculations of B-meson decay constants and masses, including extrapolations to the b-quark mass, and compares these with other theoretical and experimental results.

Findings

Decay constant f_B = 180(50) MeV

Mass of Λ_b extrapolated to continuum

Comparison with sum rule predictions

Abstract

Heavy-light bound states are studied in Lattice QCD with emphasis on parameters of the B-system relevant to experiment. Results are obtained on lattices with lattice spacings from about 0.15 fm to 0.06 fm corresponding to $\beta=5.74, 6.0$ and 6.26, and covering sizes from about 0.7 fm to 2 fm. From our results at the infinite quark mass limit and from propagating heavy quarks with mass of about 1-2.5 GeV we extrapolate to the b-quark mass to obtain the decay constant of the B-meson as well as the mass of $\Lambda_b$ in the continuum. The necessary extrapolations introduce rather large errors and lead to the value $f_B=180(50)$ MeV. We compare with the results from other lattice groups as well as with predictions coming from sum rules. The phenomenological consequences of this value of $f_B$, together with new experimental constraints, are briefly discussed.