Test of exotic scalar and tensor interactions in K_e3 decay using stopped positive kaons

TL;DR

This study measures the form factors in K+ --> pi0 e+ nu decay to test for possible exotic scalar and tensor interactions, finding results consistent with the Standard Model's zero predictions.

Contribution

The paper provides the first precise experimental determination of scalar and tensor form factors in K_e3 decay, testing for physics beyond the Standard Model.

Findings

Scalar and tensor form factors are consistent with zero within uncertainties.

Results support the Standard Model predictions for K_e3 decay.

No evidence found for exotic scalar or tensor interactions.

Abstract

The form factors of the decay K+ --> pi0 e+ nu (K_e3) have been determined from the comparison of the experimental and Monte Carlo Dalitz distributions containing about 10^5 K_e3 events. The following values of the parameters were obtained: lambda_+ = 0.0278 +- 0.0017(stat) +- 0.0015(syst), f_S/f_+(0) = 0.0040 +- 0.0160(stat) +- 0.0067(syst) and f_T/f_+(0) = 0.019 +- 0.080(stat) +- 0.038(syst). Both scalar f_S and tensor f_T form factors are consistent with the Standard Model predictions of zero values.