Observation of B$^0$ $\to$ $\psi$(2S)K$^0_\mathrm{S}\pi^+\pi^-$ and B$^0_\mathrm{S}$ $\to$ $\psi$(2S)K$^0_\mathrm{S}$ decays

TL;DR

This paper reports the first observation and measurement of branching fraction ratios for specific B meson decays involving $ ext{psi}(2S)$ and $K^0_S$ particles, using 13 TeV proton-proton collision data from the CMS experiment.

Contribution

First observation of B$^0$ $ o$ $ ext{psi}(2S)K^0_S o$ decay and measurement of its branching fraction ratio relative to B$^0$ decays, with results based on 103 fb$^{-1}$ of LHC data.

Findings

Observation of B$^0$ $ o$ $ ext{psi}(2S)K^0_S$ decay with >5 sigma significance.

Measurement of the branching fraction ratio $rac{ ext{B}(B^0_s o ext{psi}(2S)K^0_S)}{ ext{B}(B^0 o ext{psi}(2S)K^0_S)}$ as (3.33 ± 0.69 (stat) ± 0.11 (syst) ± 0.34 ($f_s/f_d$)) × 10$^{-2}$.

Measurement of the ratio $rac{ ext{B}(B^0 o ext{psi}(2S)K^0_S o ext{psi}(2S)K^0_S o)$ as 0.480 ± 0.013 (stat) ± 0.032 (syst).

Abstract

Using a data sample of $\sqrt{s} =$ 13 TeV proton-proton collisions collected by the CMS experiment at the LHC in 2017 and 2018 with an integrated luminosity of 103 fb$^{-1}$, the B$^0$ $\to$ $\psi$(2S)K$^0_\mathrm{S}$ and B$^0_\mathrm{S}$ $\to$ $\psi$(2S)K$^0_\mathrm{S}\pi^+\pi^-$ decays are observed with significances exceeding 5 standard deviations. The resulting branching fraction ratios, measured for the first time, correspond to $\mathcal{B}$(B$^0_\mathrm{S}$ $\to$ $\psi$(2S)K$^0_\mathrm{S}$) / $\mathcal{B}$(B$^0$ $\to$ $\psi$(2S)K$^0_\mathrm{S}$) = (3.33 $\pm$ 0.69 (stat) $\pm$ 0.11 (syst) $\pm$ 0.34 ($f_\mathrm{s} / f_\mathrm{d}$)) $\times$ 10$^{-2}$ and $\mathcal{B}$(B$^0$ $\to$ $\psi$(2S)K$^0_\mathrm{S}\pi^+\pi^-$) / $\mathcal{B}$(B$^0$ $\to$ $\psi$(2S)K$^0_\mathrm{S}$) = 0.480 $\pm$ 0.013 (stat) $\pm$ 0.032 (syst), where the last uncertainty in the first ratio is related to the uncertainty in the ratio of production cross sections of B$^0_\mathrm{s}$ and B$^0$ mesons, $f_\mathrm{s} / f_\mathrm{d}$.