High Precision Determination of the Q² Evolution of the Bjorken Sum

We present a significantly improved determination of the Bjorken sum for 0.6 ≤ Q2 ≤ 4.8 GeV2 using precise new gp1 and gd1 data taken with the CLAS detector at Jefferson Lab. A higher-twist analysis of the Q2 dependence of the Bjorken sum yields the twist-4 coefficient f p-n2= -0.064 ± 0.009 ± 0.032 0.036. This leads to the color polarizabilities χ p-n E= -0.032 ± 0.024 and χp-nB= 0.032 ± 0.013. The strong force coupling is determined to be α MSS (M2Z) = 0.1123 ± 0.0061, which has an uncertainty a factor of 1.5 smaller than earlier estimates using polarized deep inelastic scattering (DIS) data. This improvement makes the comparison between alpha sub(s) extracted from polarized DIS and other techniques a valuable test of QCD