TheRratio in e+e-, the determination of α (MZ2) and a possible non-perturbative gluonic contribution
A D Martin, J Outhwaite, M G Ryskin
Journal of Physics G: Nuclear and Particle Physics
We review the determination of the QED coupling at the Z pole, which is a crucial parameter for electroweak theory. We include recent e+e- -> hadron data from Novosibirsk and Beijing to re-evaluate alpha (M_Z^2). We find 1/alpha (M_Z^2) = 128.973 +/- 0.035 or 128.934 +/- 0.040 according, respectively, to whether inclusive or exclusive e+e- -> hadron data are used in the interval 1.4 < √(s) < 2.1 GeV. The error is mainly due to uncertainties in the data in the low energy region, √(s) < 2.5 GeV.
... e find that no advantage is obtained by analytic continuation of the dispersion relation into the complex s plane. We show that the hints of structure for √(s) 2.5 GeV may be evidence of a non-perturbative gluonic contribution to R(s).