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Apr 13 – 16, 2021
US/Eastern timezone

The spin of a proton: The role of the axial anomaly, emergent axion-like dynamics and the small x effective action

Apr 16, 2021, 1:50 PM
20m

Speaker

Andrey Tarasov (The Ohio State University)

Description

We discuss the role of the chiral “triangle” anomaly in deeply inelastic scattering (DIS) of electrons off polarized protons employing a powerful worldline formalism which allows for the efficient computation of perturbative multi-leg Feynman amplitudes. We demonstrate how the triangle anomaly appears at high energies in the DIS "box diagram" for the polarized structure function $g_1(x_B, Q^2)$ in both the Bjorken limit of large $Q^2$ and in the Regge limit of small $x_B$. We show for the first time that the off-forward infrared pole of the anomaly appears in both limits. We motivate a small x effective action, consistent with anomalous chiral Ward identities, that shows how non-perturbative effects cancel the infrared pole, leading to an effective axion-like dynamics at small x. There are two non-perturbative scales that control this dynamics: one is the saturation scale and the other is the pure Yang-Mills topological susceptibility; we discuss how their dynamical inter play can be uncovered in polarized DIS at the Electron-Ion Collider.

Primary authors

Andrey Tarasov (The Ohio State University) Dr Raju Venugopalan (Brookhaven National Laboratory)

Presentation materials