A New B-Quark Mass Measurement

A new determination of the mass of a b-quark (sometimes called a bottom quark and sometimes called a beauty quark) incorporating electromagnetic effects rather than merely strong force interactions for the first time, largely confirms prior estimates. 

The Particle Data Group global average is 4.18 + 0.03 - 0.03 GeV.

We extend HPQCD's earlier nf=4 lattice-QCD analysis of the ratio of MSB⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ masses of the b and c quark to include results from finer lattices (down to 0.03fm) and a new calculation of QED contributions to the mass ratio. We find that m⎯⎯⎯⎯b(μ)/m⎯⎯⎯⎯c(μ)=4.586(12) at renormalization scale μ=3\,GeV. This result is nonperturbative. Combining it with HPQCD's recent lattice QCD+QED determination of m⎯⎯⎯⎯c(3GeV) gives a new value for the b-quark mass: m⎯⎯⎯⎯b(3GeV)=4.513(26)GeV. The b-mass corresponds to m⎯⎯⎯⎯b(m⎯⎯⎯⎯b,nf=5)=4.202(21)GeV. These results are the first based on simulations that include QED.

D. Hatton, et al., "Determination of m(b)/m(c) and m(b) from n(f)=4 lattice QCD+QED" arXiv:2102.09609 [hep-lat] (February 18, 2021).