First evidence of the $B_s^0\to K^{-}\ddot{I}{€}^{+}{\hat{I}}^3$ decay

Abstract

The first search for the $B_s^0\to K^{-}\ddot{I}{€}^{+}{\hat{I}}^3$ decay in the range $796<m(K^{-}\ddot{I}{€}^{+})<1800\text{MeV/}{c}^2$ is performed using data from proton-proton collisions collected by the LHCb experiment at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb${}^{-1}$. The photons are reconstructed through their conversion into an electron-positron pair, which significantly improves the mass resolution of the reconstructed decays with respect to decays with an unconverted photon. A signal excess with a significance of 3.5 standard deviations is measured, constituting the first experimental evidence for this decay. In the range $796<m(K^{-}\ddot{I}{€}^{+})<996\text{MeV/}{c}^2$, the ratio $\mathcal{R}$ between the branching fractions of the signal decay and the favoured $\overline{B}{}^0\to K^{-}\ddot{I}{€}^{+}{\hat{I}}^3$ decay is measured to be $\mathcal{R}=(3.7\pm 1.2\pm 0.4)\times 10^{-2}$ where the first uncertainty is statistical and the second is systematic. This measurement is consistent with the value predicted in the Standard Model. In the range $996<m(K^{-}\ddot{I}{€}^{+})<1800\text{MeV/}{c}^2$, the ratio $\mathcal{R}=(0.2\pm 2.7\pm 1.3)\times 10^{-2}$ is measured.

All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://lbfence.cern.ch/alcm/public/analysis/full-details/5390/ (LHCb public pages)