Updated determination of the pion-photon transition form factor

2023/10/24 by Hua Zhou, Yan Jiang, Qing Yu +1 · 1 voice
Physics and Astronomy · #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #High-Energy Particle Collisions Research

paper · pdf · doi:10.1103/physrevd.108.074020

openalex publication_date 2023/10/24 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/25

Abstract

In this paper, we study the properties of the pion-photon transition form factor (TFF), \ensuremathγ\ensuremathγ^*\ensuremath→\ensuremathπ⁰, by using the principle of maximum commonality (PMC) to deal with its perturbative QCD contribution up to next-to-next-to-leading order QCD corrections. Applying the PMC, we achieve precise pQCD prediction for the TFF in a large Q²-region without conventional renormalization scale ambiguity. We also discuss the power suppressed nonvalence quark contribution to the TFF, which is important for a sound prediction in a low and intermediate Q²-region, e.g. the nonvalence quark components affect the TFF by about 1% to 23% when Q² changes down from 40 GeV² to 4 GeV². The resultant pion-photon TFF shows a better agreement with previous Belle data. It is hoped that previous discrepancies between the experimental measurements and theoretical predictions could be clarified by the forthcoming precise data on the Belle II measurements.

Citations

• Anomalous Ward Identities in Spinor Field Theories
• Measurement of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>γ</mml:mi><mml:msup><mml:mi>γ</mml:mi><mml:mo>*</mml:mo></mml:msup><mml:mo>→</mml:mo><mml:msup><mml:mi>π</mml:mi><mml:mn>0</mml:mn></mml:msup></mml:math>transition form factor
• Measurement of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>γ</mml:mi><mml:msup><mml:mi>γ</mml:mi><mml:mo>*</mml:mo></mml:msup><mml:mo>→</mml:mo><mml:msup><mml:mi>π</mml:mi><mml:mn>0</mml:mn></mml:msup></mml:math>transition form factor at Belle
• Axial-Vector Vertex in Spinor Electrodynamics
• Review of Particle Physics

Discussions

• The initial valence quark assignment for the neutral pion came from the quark model, but the best direct experimental constraint on the quark content of the $\pi^0$ probably comes from its measured tw [stackexchange, 1 points]

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