Neutral Pion Lifetime Measurements and the QCD Chiral Anomaly

Abstract

A fundamental property of QCD is the presence of the chiral anomaly, which is the primary component of the ${\pi }^0\to \gamma \gamma$ decay amplitude. Based on this anomaly and its small ($\simeq$ 4.5%) chiral correction, a firm prediction of the ${\pi }^0$ lifetime can be used as a test of QCD at confinement scale energies. The interesting experimental and theoretical histories of the ${\pi }^0$ meson are reviewed, from discovery to the present era. Experimental results are in agreement with the theoretical prediction, within the current ($\simeq$ 3%) experimental error; however, they are not yet sufficiently precise to test the chiral corrected result, which is a firm QCD prediction and is known to $\simeq$ 1% uncertainty. At this level there exist experimental inconsistencies, which require attention. Possible future work to improve the present precision is suggested.

75 pages, 17 figures

References in corpus (9)

• A New Measurement of the ${\pi }^0$ Radiative Decay Width
• The $\eta$ and ${\eta }^{\prime }$ mesons from Lattice QCD
• New Precise Measurement of the Pion Weak Form Factors in the Pi+ -> e+ nu gamma Decay
• Axial anomaly and the precise value of the ${\pi }^0\to 2\gamma$ decay width
• On the Radiative Pion Decay
• On the possibility to measure the (pi0 to gamma gamma) decay width and the (gamma* gamma to pi0) transition form factor with the KLOE-2 experiment
• Determination of the Parity of the Neutral Pion via the Four-Electron Decay
• Neutral pion photoproduction at high energies
• Photoproduction of Pseudoscalar Mesons off Nuclei at Forward Angles

Cited by in corpus (23)

• Quantum field theory in a magnetic field: From quantum chromodynamics to graphene and Dirac semimetals
• QCD and strongly coupled gauge theories: challenges and perspectives
• The pion: an enigma within the Standard Model
• Dispersive analysis of the pion transition form factor
• Experimental observation of anisotropic Adler-Bell-Jackiw anomaly in type-II Weyl semimetal WTe${}_{1.98}$ crystals at the quasi-classical regime
• Precision tests of fundamental physics with $\eta$ and ${\eta }^{\prime }$ mesons
• On the precision of a data-driven estimate of hadronic light-by-light scattering in the muon g-2: pseudoscalar-pole contribution
• Lattice QCD calculation of hadronic light-by-light scattering
• Radiative resonance couplings in $\gamma \pi \to \pi \pi$
• The NMSSM lives: with the 750 GeV diphoton excess
• Light Dark Sectors through the Fermion Portal
• Leading logarithms in the anomalous sector of two-flavour QCD
• Experimental study of rare charged pion decays
• Strong Interaction Physics at the Luminosity Frontier with 22 GeV Electrons at Jefferson Lab
• Lorentz invariance violation as an explanation of muon excess in Auger data
• Anomalous plasma: chiral magnetic effect and all that
• Dispersive approach to non-Abelian axial anomaly
• Strongly interacting matter in extreme magnetic fields
• The Antiparticles of Neutral Bosons
• Transition form-factor of $\gamma \to 3\pi$ in nonlocal quark model
• Chiral perturbation theory
• Tests of Three-Flavor Chiral Perturbation Theory
• PEN: a low energy test of lepton universality