The polarized Bjorken sum rule analysis: revised

Abstract

We present progress in the QCD analysis of the Bjorken sum rule at low momentum transfers. We study asymptotic structure of the perturbative QCD expansion at low Q 2 scales based on analysis of recent accurate data on the Bjorken sum rule and available now four-loop expression for the coefficient-function CBj (Q 2 ). We demonstrate that the standard perturbative series for CBj (Q 2 ) gives a hint to its asymptotic nature manifesting itself in the region Q 2 1 GeV 2 . It is confirmed by the considered integral model for the perturbative QCD correction. We extract a value of highertwist µ4 coefficient and study the interplay between higher orders and higher-twist contributions. Results of other approaches to the description of Bjorken sum rule data are discussed.

Massless Propagators, $R(s)$ and Multiloop QCD

“…Moreover, the corresponding curve passes close to the central values of several data points, although the experimental accuracy (which is of the same order as both the three-and four-loop contributions) does not allow one to make a definite choice between four-and three-loop approximations." Second, a certain duality between higher orders and higher-twist contributions to the Bjorken sum rule (74) has been detected 6 in [87]. Indeed, the fitted value of first non-zero higher twist contribution, µ 4 , has proved to be strongly dependent on the order of PT terms kept in (79).…”

“…For the QCD case gauge we have found full agreement between eqs. (82)(83)(84)(85)(86)(87)(88)(89)(90)(91)(92)(93) and results of [99].…”

“…Phenomelogical implications of (79) have been studied in works [86,87]. Their results can be summarized as follows.…”