New determination of the branching ratio of the structure dependent radiative $K^{+}\to e^{+}{\nu }_e\gamma$ decay

Abstract

The branching ratio of the structure dependent (SD) radiative $K^{+}\to e^{+}{\nu }_e\gamma$ decay relative to that of the $K^{+}\to e^{+}{\nu }_e(\gamma )$ decay including the internal bremsstrahlung (IB) process ($K_{e2(\gamma )}$) has been measured in the J-PARC E36 experiment using plastic scintillator/lead sandwich detectors. In the analysis, the effect of IB was also taken into account in the SD radiative decay as $K_{e2\gamma (\gamma )}^{\mathrm{SD}}$. By combining the new data with the previously reported result of the E36 experiment using a CsI(Tl) calorimeter after revision for the IB correction for $K_{e2\gamma (\gamma )}^{\mathrm{SD}}$, a new value $Br(K_{e2\gamma (\gamma )}^{\mathrm{SD}})/Br(K_{e2(\gamma )})=1.20\pm 0.07$ has been determined, which is consistent with a recent lattice QCD calculation, but larger than the expectation of Chiral Perturbation Theory (ChPT) at order $O(p^4)$ and the previous KLOE value. Also, using the method to relate form factor and branching ratio described in the KLOE paper, the present result is consistent with the form factor prediction based on a gauged nonlocal chiral quark model, but larger than ChPT at order $O(p^6)$.

19 pages

References in corpus (5)

• The Standard Model prediction for R_{e/mu}^{(pi,K)}
• Magnetic susceptibility of the QCD vacuum
• Comparison of lattice QCD+QED predictions for radiative leptonic decays of light mesons with experimental data
• Fabrication of silica aerogel with $n$ = 1.08 for $e^{+}/{\mu }^{+}$ separation in a threshold Cherenkov counter of the J-PARC TREK/E36 experiment
• The design and basic performance of a Spiral Fiber Tracker for the J-PARC E36 experiment

Cited by in corpus (1)

• Kaon radiative leptonic decay rates from lattice QCD simulations at the physical point