Speaker
Description
We evaluate the polarised Bjorken sum rule (BSR) $\overline{\Gamma}^{p-n}_1(Q^2)$ with truncated Operator Product Expansion (OPE) up to the $D=4$ term [1]. Due to the knowledge of the renormalon structure of the BSR, the leading-twist term of dimension $D=0$ is evaluated using a recently developed renormalon-based resummation [2], in this case with two variants of holomorphic QCD couplings [$a(Q^2) \mapsto {\mathcal A}(Q^2)$] which have no Landau singularities and thus require, in contrast to the perturbative QCD (pQCD) case [3], no regularisation of the resummation formula. The $D=2$ and $D=4$ terms are then included in the OPE of the inelastic BSR, and fits are performed to the available experimental data.
In comparison to applying the renormalon-based resummation method using the pQCD coupling, further advantages we note in our approach are that the $Q^2$-interval in the fit can be significantly extended to lower $Q^2$-values and the extracted residue parameter values are more stable, this being reflected in the significantly reduced experimental uncertainties of these values.
References:
[1] C. Ayala, C. Castro-Arriaza and G. Cvetič, Nucl. Phys. B 1007, 116668 (2024).
[2] G. Cvetič, Phys. Rev. D 99 no.1, 014028 (2019).
[3] C. Ayala, C. Castro-Arriaza and G. Cvetič, Phys. Lett. B 848, 138386 (2024).
