Measurements of the K+→π0e+ν form factors

π → lνγ form factors at two-loop

“…[18]. Looking at K + → π 0 νe + as was done in [19] could not rule out the possibility of a small tensorial term in the amplitude.…”

Unitarity, chiral perturbation theory, and meson form factors

“…Therefore, in the experimental search for scalar and tensor couplings in the K l3 decays, these nonlinearities should be included in the analysis of the experimental data. The most recent experimental measurement points towards the conclusion that the presence of scalar and tensor couplings or nonlinearities in the f Kπ + form factor cannot be excluded [26]. However, this conclusion has to await verification from forthcoming kaon facilities such as DAΦNE [25].…”

Search for tensor interactions in kaon decays at DAΦNE

“…Fitting Dalitz plot to the distribution ρ(E π , E e ) leads to nonzero values of the form factors |F S /f + (0)| = 0.070 ± 0.016 and |F T /f + (0)| = 0.53 ± 0.10 [2]. An analysis was provided in terms of linearly parametrized f + (Q 2 ) = f + (0) [1 + λ + Q 2 /m 2 π ] and constants F S and F T .…”

“…The contribution of the electroweak radiative corrections to the scalar and tensor form factors is negligibly small. Therefore, the appearance of a considerable nonzero scalar and tensor form factors [16,2] points to deviations from the standard V -A interaction. The term in the vector matrix element with f − (Q 2 ) can be reduced (using Dirac equation) to the scalar form factor:…”

“…The recent experiments on semileptonic meson decays [1,2] point to the possible existence of an admixture of tensor interactions [3,4], which can help to reconcile [5] the results of the previous experiments [6]. Unfortunately, the experimental data is poor and the experimental status of the form factors determination of the three particles semileptonic decays is obscure [7].…”