QED in (B)over-bar →<(K)over bar>l +l- LFU ratios: theory versus experiment, a Monte Carlo study

Using analytic results obtained in a meson effective theory, that includes all infrared sensitive logs, we build a dedicated Monte Carlo framework to describe QED corrections in (B) over bar (0) -> (K) over barl+l(-) for a generic form factor. For the neutral mode (B) over bar (0) -> (K) over bar (0)l+l(-), we perform a detailed numerical comparison versus those obtained with the general-purpose photon-shower tool PHOTOS. The comparison indicates a good agreement, at the few per-mil level, when focusing on the rare mode only. In addition, our framework allows us to investigate the impact of the charmonium resonances. Interference effects, not described by PHOTOS in the experimental analysis, are found to be small in the dilepton invariant mass region q(2) < 6GeV(2), which is used to determine R-K(*). Using a semi-analytic framework we assess the full, rare and resonant, mode. Based thereupon, we discuss strategies to check the subtraction of the resonant mode, which has a sizeable impact at q(2) approximate to 6GeV(2) in the electron mode.

Automated summary

Using meson effective theory and a Monte Carlo framework, this study investigates the QED corrections in (B) over bar (0) -> (K) over barl+l(-). The comparison with the general-purpose photon-shower tool PHOTOS shows a good agreement in the rare mode, and interference effects in the dilepton invariant mass region are found to be small. The impact of charmonium resonances is also discussed.