Speaker
Описание
Using the dispersive approach to the axial anomaly, both Abelian and non-Abelian cases are considered. Anomalous sum rules for isovector, octet and singlet currents are derived and transition form factors of $\pi^0,\eta,\eta'$ mesons are obtained in the both space- and time-like regions. Also this approach allow us to express the nonperturbative gluon matrix element $\langle 0 |G\tilde{G}|\gamma\gamma^{(*)} \rangle$ from experimentally measured transition form factors $\pi^0,\eta,\eta'\rightarrow\gamma\gamma^{(*)}$ and describe it as a function of the photon virtuality. This matrix element differs from the matrix element $\langle 0 |G\tilde{G}|\gamma Z^{0} \rangle$ up to $\frac{1}{m_{W}^2}$ corrections only by a charge factor. Thus one can predict behaviour of the matrix element $\langle 0 |G\tilde{G}|\gamma Z^{0} \rangle$ as a function of $Z^0$ momentum in $\pi^{0},\eta\rightarrow \nu \bar{\nu} \gamma$ Dalitz decays. The decay widths of such processes were calculated, which may contribute to background in dark matter searches.
