Axial Currents of Virtual Charm in Light Quark Processes

TL;DR

This paper investigates the role of virtual charm axial currents in B-meson decays and nucleon spin structure, using instanton QCD vacuum models to derive effective actions and compute charm contributions.

Contribution

It introduces a rederivation of the Dyakonov-Petrov effective action within the instanton vacuum model to analyze virtual charm effects in hadronic processes.

Findings

Calculated the charm contribution to eta' coupling: -12.3 to -18.4 MeV.

Estimated the charm spin contribution in the nucleon: -0.015 to -0.024.

Provided explanations for recent B-meson decay experimental data.

Abstract

The systematic investigations of the role of the virtual charm axial currents in the decay of $B$-mesons to $\eta '$ $K$ and the spin structure of the nucleon are performed. We reduce the divergence of the virtual charm axial current to a specific gluon operator. Since this operator receives the main contribution from topologically nontrivial components of the QCD vacuum, we rederive the Dyakonov-Petrov Effective Action, based on the instanton QCD vacuum model. This action is applied to the calculations of the coupling of $\eta '$ to the charm axial current and found $f_{\eta '}^{(c)} (\mu \simeq m_c) = - (12.3 \sim 18.4 {\rm MeV}), $ providing a possibility for the explanations of the recent experimental data on $B \to \eta ' K$-decay. Analogous calculations of the virtual charm content of the nucleon spin leads to $\Delta c (\mu \simeq m_c) = - (0.015 \sim 0.024),$ which is one order of magnitude smaller than the analogous contribution of the strange quark.