Seminar “Hadron Physics”

Date and Time: Friday, 7 October 2022, at 11:00 AM

Venue: Blokhintsev lecture hall (4th floor), Bogoliubov Laboratory of Theoretical Physics; online seminar on Zoom

Information about seminar and link to join via Zoom

Seminar topic: “Gluon anomaly in the dispersive approach and transition form factors of pseudoscalar mesons”

Speaker: Sergey Khlebtsov (NRC “Kurchatov Institute” – ITEP)

Abstract:

The dispersive approach to axial anomaly was generalized to a non-Abelian case with arbitrary photon virtualites. We derive the anomaly sum rule for the singlet current and obtain the π⁰, η,η^′ → γγ^(∗) transition form factors. The relevant low energy theorem was generalized to the case of mixed states and used to evaluate the subtraction constant of the strong anomaly-related form factor ⟨0|GG̃|γγ⟩. Using expressions for transition form factors, we established the behaviour of a non-perturbative gluon matrix element ⟨0|GG̃|γγ^∗ (q²)⟩ in both space-like and time-like regions. We found a significant contribution of the non-Abelian axial anomaly to the processes with one virtual photon, comparable to that of the electromagnetic anomaly. From the analysis of the experimental data we established existence of a non-zero π⁰ − η − η^′ mixing. The possibility of a light pseudoscalar glueball-like state is conjectured.