Direct measurement of the lifetime of the neutral pion

Electromagnetic axial anomaly in a generalized linear sigma model

“…where the subscripts 1, 2 and 3 refer to [31], [32] and [33] respectively. Unfortunately there is no experimental data regarding the decay rates of π ′ 0p , η 3 and η 4 .…”

“…We apply Eq. (50) together with the numerical values for all the parameters involved computed in [8] to determine the theoretical decay rates summarized in Table I [31] 7.74 ± 0.66 × 10 −3 [32] 7.82 ± 0.14 × 10 −3 [33] Γ(π ′ 0p → γγ)…”

Chiral expansions of pi0 decays

“…The experimental situation then was the same as it is now according to the accepted numbers by the particle data group (PDG) [2]. At that time a new experimental prediction from CERN-NA030 [11] suggested a smaller value for the partial width 7.25 ± 0.23 eV (statistical and systematic errors combined in quadrature). Older experiments (Tomsk, Desy and Cornell [12]), seemed not to be so precise (7.23 ± 0.55, 11.7 ± 1.2, 7.92 ± 0.42 eV, respectively); they relied on the so-called Primakoff effect [13] that is based on…”

Test Fundamental Symmetries via Precision Measurements of \(\pi ^{0}\), \(\eta \), and \(\eta '\) Decays

“…The left hand side shaded band is the recent QCD sum rule prediction [5] and the right hand side shaded band is the next-to-leading order chiral theory predictions [2,3]. The experimental results with errors from the left are for: (1) the direct method [7]; (2, 3, 4) the Primakoff method [8][9][10]; (5) published PrimEx-I result [11]. The last point on the right represents the expected error for the PrimEx-II experiment arbitrarily plotted to agree with the leading order prediction.…”