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

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## Abstract

First observations of the $B^0_s \rightarrow \psi(2S) \eta$, $B^0 \rightarrow \psi(2S) \pi^+ \pi^-$ and $B^0_s \rightarrow \psi(2S) \pi^+ \pi^-$ decays are made using a dataset corresponding to an integrated luminosity of 1.0 $fb^{-1}$ collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=7$ TeV. The ratios of the branching fractions of each of the $\psi(2S)$ modes with respect to the corresponding $J/\psi$ decays are $\frac{\mathcal{B}(B^0_s \rightarrow \psi(2S) \eta) }{\mathcal{B}(B^0_s \rightarrow J/\psi \eta)} =0.83\pm0.14 (stat)\pm0.12 (syst)\pm0.02 (\mathcalB}),$ $\frac{\mathcal{B}(B^0 \rightarrow \psi(2S) \pi^+ \pi^-)}{\mathcal{B}(B^0 \rightarrow J/\psi \pi^+ \pi^-)} =0.56\pm0.07 (stat)\pm0.05 (syst)\pm0.01 (\mathcal{B}),$ $\frac{\mathcal{B}(B^0_s \rightarrow \psi(2S) \pi^+ \pi^-)}{\mathcal{B}(B^0_s \rightarrow J/\psi \pi^+ \pi^-)} =0.34\pm0.04 (stat)\pm0.03 (syst)\pm0.01 (\mathcal{B}),$ where the third uncertainty corresponds to the uncertainties of the dilepton branching fractions of the $J/\psi$ and $\psi(2S)$ meson decays.

## Figures and captions

 Mass distributions of (a) $B ^{0}_{\mathrm{(s)}} \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \eta$ and (b) $B ^{0}_{\mathrm{(s)}} \rightarrow \psi {(2\mathrm{S})} \eta$ candidates. The total fit function (solid black) and the combinatorial background (dashed) are shown. The solid red lines show the signal $B ^0_ s$ contribution and the red dot dashed line corresponds to the $B ^0$ contribution. Fig_1.pdf [73 KiB] HiDef png [173 KiB] Thumbnail [159 KiB] *.C file tex code Background subtracted (a) $\gamma \gamma$ and (b) $\mu ^+\mu ^-$ mass distributions in $B ^0_ s \rightarrow \psi {(2\mathrm{S})} \eta$ decays. In both cases the blue line is the result of the fit described in the text. Fig_2.pdf [75 KiB] HiDef png [132 KiB] Thumbnail [113 KiB] *.C file tex code Mass distributions of (a) $B ^{0}_{\mathrm{(s)}} \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \pi ^+\pi ^-$ and (b) $B ^{0}_{\mathrm{(s)}} \rightarrow \psi {(2\mathrm{S})} \pi ^+\pi ^-$ candidates. The total fit function (solid black) and the combinatorial background (dashed) are shown. The solid red lines show the signal $B ^0_ s$ contribution and the red dot dashed lines correspond to the $B ^0$ contributions. The reflections from misidentified $B ^0 \rightarrow \psi K ^{*0}$, $K ^{*0} \rightarrow K ^+ \pi ^-$ decays are shown with dotted blue lines. Fig_3.pdf [90 KiB] HiDef png [204 KiB] Thumbnail [170 KiB] *.C file tex code Background subtracted $\pi ^+\pi ^-$ mass distribution in (a) $B ^0 \rightarrow \psi {(2\mathrm{S})} \pi ^+\pi ^-$ and (b) $B ^0_ s \rightarrow \psi {(2\mathrm{S})} \pi ^+\pi ^-$ (black points). The red filled area shows the expected signal spectrum for the $\psi {(2\mathrm{S})}$ channel derived from the measured spectrum of the ${ J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}$ channel (the fit has one parameter --- the normalisation). The width of the band corresponds to the uncertainties of the distribution from the ${ J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}$ channel. In case of $B ^0 \rightarrow \psi {(2\mathrm{S})} \pi ^+\pi ^-$, the blue vertical filled area shows the $K ^0_{\rm\scriptscriptstyle S}$ region that is excluded from the fit. Fig_4.pdf [88 KiB] HiDef png [219 KiB] Thumbnail [150 KiB] *.C file tex code Animated gif made out of all figures. PAPER-2012-053.gif Thumbnail

## Tables and captions

 Fitted values of signal events ($N_{\mathrm{B}}$), signal peak position ($\mathrm{M}_{\mathrm{B}}$) and resolution ($\sigma_{\mathrm{B}}$). The quoted uncertainties are statistical only. Table_1.pdf [51 KiB] HiDef png [40 KiB] Thumbnail [19 KiB] tex code Fitted values of signal events ($N_{\mathrm{B}}$), signal peak position ($\mathrm{M}_{\mathrm{B}}$) and resolution ($\sigma_{\mathrm{B}}$). The quoted uncertainties are statistical only. Table_2.pdf [57 KiB] HiDef png [65 KiB] Thumbnail [33 KiB] tex code Relative systematic uncertainties (in %) of the relative branching fractions. Table_3.pdf [53 KiB] HiDef png [49 KiB] Thumbnail [22 KiB] tex code

Created on 19 February 2021.