1S and MS¯ bottom quark masses from Υ sum rules

The bottom quark 1S mass M^1S_b is determined using sum rules which relate the masses and the electronic decay widths of the Υ mesons to moments of the vacuum polarization function. The 1S mass is defined as half the perturbative mass of a fictitious ³S₁ bottom-quark-bottom-antiquark bound state, and is free of the ambiguity of order Λ_QCD which plagues the pole mass definition. Compared to an earlier analysis by the same author, which had been carried out in the pole mass scheme, the 1S mass scheme leads to a much better behaved perturbative series of the moments, smaller uncertainties in the mass extraction and a reduced correlation of the mass and the strong coupling. We arrive at M^1S_b=4.71+/-0.03 GeV, taking α_s(M_Z)=0.118+/-0.004 as an input. From that we determine the MS¯ mass as m¯_b(m¯_b)=4.20+/-0.06 GeV. The error in m¯_b(m¯_b) can be reduced if the three-loop corrections to the relation of pole and MS¯ mass are known and if the error in the strong coupling is decreased.