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CMS-BPH-18-004 ; CERN-EP-2021-271
Observation of B0ψ(2S)K0Sπ+π and B0sψ(2S)K0S decays
Eur. Phys. J. C 82 (2022) 499
Abstract: Using a data sample of s= 13 TeV proton-proton collisions collected by the CMS experiment at the LHC in 2017 and 2018 with an integrated luminosity of 103 fb1, the B0sψ(2S)K0S and B0ψ(2S)K0Sπ+π decays are observed with significances exceeding 5 standard deviations. The resulting branching fraction ratios, measured for the first time, correspond to B(B0sψ(2S)K0S)/B(B0ψ(2S)K0S)= (3.33 ± 0.69 (stat) ± 0.11 (syst) ± 0.34 (fs/fd)) × 102 and B(B0ψ(2S)K0Sπ+π)/B(B0ψ(2S)K0S)= 0.480 ± 0.013 (stat) ± 0.032 (syst), where the last uncertainty in the first ratio is related to the uncertainty in the ratio of production cross sections of B0s and B0 mesons, fs/fd.
Figures & Tables Summary References CMS Publications
Figures

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Figure 1:
Measured invariant mass distributions of ψ(2S)K0S (left) and ψ(2S)K0Sπ+π (right) candidates. The overlaid results from the fit are described in the text.

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Figure 1-a:
Measured invariant mass distribution of ψ(2S)K0S candidates. The overlaid results from the fit are described in the text.

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Figure 1-b:
Measured invariant mass distribution of ψ(2S)K0Sπ+π candidates. The overlaid results from the fit are described in the text.

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Figure 2:
Distributions of 2-body intermediate invariant masses from the B0ψ(2S)K0Sπ+π decay. The data distributions (black dots) are background subtracted. Overlaid are the predictions of phase space simulations (red triangles), as well as the predictions after applying the reweighting procedure described in Section 7 (grey squares).

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Figure 2-a:
Distribution of the π+π invariant mass from the B0ψ(2S)K0Sπ+π decay. The data distribution (black dots) is background subtracted. Overlaid are the predictions of phase space simulations (red triangles), as well as the predictions after applying the reweighting procedure described in Section 7 (grey squares).

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Figure 2-b:
Distribution of the ψ(2SK0S invariant mass from the B0ψ(2S)K0Sπ+π decay. The data distribution (black dots) is background subtracted. Overlaid are the predictions of phase space simulations (red triangles), as well as the predictions after applying the reweighting procedure described in Section 7 (grey squares).

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Figure 2-c:
Distribution of the ψ(2Sπ invariant mass from the B0ψ(2S)K0Sπ+π decay. The data distribution (black dots) is background subtracted. Overlaid are the predictions of phase space simulations (red triangles), as well as the predictions after applying the reweighting procedure described in Section 7 (grey squares).

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Figure 2-d:
Distribution of the K0Sπ invariant mass from the B0ψ(2S)K0Sπ+π decay. The data distribution (black dots) is background subtracted. Overlaid are the predictions of phase space simulations (red triangles), as well as the predictions after applying the reweighting procedure described in Section 7 (grey squares).

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Figure 2-e:
Distribution of the ψ(2Sπ+ invariant mass from the B0ψ(2S)K0Sπ+π decay. The data distribution (black dots) is background subtracted. Overlaid are the predictions of phase space simulations (red triangles), as well as the predictions after applying the reweighting procedure described in Section 7 (grey squares).

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Figure 2-f:
Distribution of the K0Sπ+ invariant mass from the B0ψ(2S)K0Sπ+π decay. The data distribution (black dots) is background subtracted. Overlaid are the predictions of phase space simulations (red triangles), as well as the predictions after applying the reweighting procedure described in Section 7 (grey squares).

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Figure 3:
Distributions of 3-body intermediate invariant masses from the B0ψ(2S)K0Sπ+π decay. Data distributions (black dots) are background subtracted. Overlaid are the predictions of phase space simulations (red triangles), as well as the predictions after applying the reweighting procedure described in Section 7 (grey squares).

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Figure 3-a:
Distribution of the ψ(2S)π+π invariant mass from the B0ψ(2S)K0Sπ+π decay. The data distribution (black dots) is background subtracted. Overlaid are the predictions of phase space simulations (red triangles), as well as the predictions after applying the reweighting procedure described in Section 7 (grey squares).

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Figure 3-b:
Distribution of the K0Sπ+π invariant mass from the B0ψ(2S)K0Sπ+π decay. The data distribution (black dots) is background subtracted. Overlaid are the predictions of phase space simulations (red triangles), as well as the predictions after applying the reweighting procedure described in Section 7 (grey squares).

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Figure 3-c:
Distribution of the ψ(2S)K0Sπ+ invariant mass from the B0ψ(2S)K0Sπ+π decay. The data distribution (black dots) is background subtracted. Overlaid are the predictions of phase space simulations (red triangles), as well as the predictions after applying the reweighting procedure described in Section 7 (grey squares).

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Figure 3-d:
Distribution of the ψ(2S)K0Sπ invariant mass from the B0ψ(2S)K0Sπ+π decay. The data distribution (black dots) is background subtracted. Overlaid are the predictions of phase space simulations (red triangles), as well as the predictions after applying the reweighting procedure described in Section 7 (grey squares).

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Figure 4:
Background-subtracted pT(B0) distribution in data for the B0ψ(2S)K0S signal. The last bin includes the overflow.
Tables

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Table 1:
Systematic uncertainties (in %) of the measured branching fraction ratios.
Summary
The B0sψ(2S)K0S and B0ψ(2S)K0Sπ+π decays are observed using proton-proton collision data collected by the CMS experiment at 13 TeV with an integrated luminosity of 103 fb1. Their branching fractions are measured with respect to the B0ψ(2S)K0S decay to be B(B0sψ(2S)K0S)/B(B0ψ(2S)K0S)= (3.33 ± 0.69 (stat) ± 0.11 (syst) ± 0.34 (fs/fd)) × 102, and B(B0ψ(2S)K0Sπ+π)/B(B0ψ(2S)K0S)= 0.480 ± 0.013 (stat) ± 0.032 (syst), where the last uncertainty in the first ratio corresponds to the uncertainty in the ratio of production cross sections of B0s and B0 mesons. The 2- and 3-body invariant mass distributions of the B0ψ(2S)K0Sπ+π decay products do not show significant exotic narrow structures in addition to the known light meson resonances. Further studies with more data will be needed to investigate more precisely the internal dynamics of the B0ψ(2S)K0Sπ+π decay, and to perform CP asymmetry measurements in the two observed decays in the future.
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