With vector-meson effects included, the WZW anomalous coupling extracted from eta-prime to pi+ pi- gamma matches theory and implies a box-anomaly branching fraction about an order of magnitude larger than the published value.
New measurement of the charged kaon semileptonic (Ke4) decay Branching Ratio and Hadronic Form Factors
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abstract
A sample of more than one million Ke4 decay candidates with less than one percent background contamination has been collected by the NA48/2 experiment at the CERN SPS in 2003-2004, allowing a detailed study of the decay properties. The branching ratio, inclusive of radiative Ke4gamma decays, is measured to be BR(Ke4) = (4.257 +/- 0.016_exp +/- 0.031_ext) x 10-5 with a total relative error of 0.8%. This measurement complements the study of S- and P-wave hadronic form factors by assigning absolute values to the relative hadronic form factors obtained earlier in a simultaneous analysis of the pion-pion scattering lengths conducted on the same data sample. The overall form factor normalization f_s = 5.705 +/- 0.017_exp +/- 0.031_ext is obtained with a total relative precision of 0.6%.
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Identify hadron anomalous couplings at colliders
With vector-meson effects included, the WZW anomalous coupling extracted from eta-prime to pi+ pi- gamma matches theory and implies a box-anomaly branching fraction about an order of magnitude larger than the published value.