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CMS-BPH-16-003 ; CERN-EP-2018-224
Studies of Bs2(5840)0Bs2(5840)0 and Bs1(5830)0Bs1(5830)0 mesons including the observation of the Bs2(5840)0B0K0SBs2(5840)0B0K0S decay in proton-proton collisions at s=s= 8 TeV
Eur. Phys. J. C 78 (2018) 939
Abstract: Measurements of Bs2(5840)0Bs2(5840)0 and Bs1(5830)0Bs1(5830)0 mesons are performed using a data sample of proton-proton collisions corresponding to an integrated luminosity of 19.6 fb11 , collected with the CMS detector at the LHC at a centre-of-mass energy of 8 TeV. The analysis studies PP-wave B0sB0s meson decays into B()+KB()+K and B()0K0SB()0K0S, where the B+B+ and B0B0 mesons are identified using the decays B+J/ψK+B+J/ψK+ and B0J/ψK(892)0B0J/ψK(892)0. The masses of the PP-wave B0sB0s meson states are measured and the natural width of the Bs2(5840)0Bs2(5840)0 state is determined. The first measurement of the mass difference between the charged and neutral BB mesons is also presented. The Bs2(5840)0Bs2(5840)0 decay to B0K0SB0K0S is observed, together with a measurement of its branching fraction relative to the Bs2(5840)0B+KBs2(5840)0B+K decay.
Figures & Tables Summary References CMS Publications
Figures

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Figure 1:
Invariant mass distributions of (a) J/ψK+J/ψK+ and (b) J/ψK0J/ψK0 candidates in data with the fit results superimposed. The points represent the data, with the vertical bars giving the corresponding statistical uncertainties. The thick curves are results of the fits, the dash-dotted lines display the signal contributions, and the short-dashed lines show the combinatorial background contributions. The long-dashed line shows in (a) the contribution from the B+J/ψπ+B+J/ψπ+ decay, and in (b) the contribution from partially reconstructed BJ/ψK0XBJ/ψK0X decays. The dashed line in (b) displays the contribution from swapping K±π±K±π± in the reconstruction.

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Figure 1-a:
Invariant mass distribution of J/ψK+J/ψK+ candidates in data with the fit results superimposed. The points represent the data, with the vertical bars giving the corresponding statistical uncertainties. The thick curves are results of the fits, the dash-dotted lines display the signal contributions, and the short-dashed lines show the combinatorial background contributions. The long-dashed line shows the contribution from the B+J/ψπ+B+J/ψπ+ decay.

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Figure 1-b:
Invariant mass distribution of J/ψK0J/ψK0 candidates in data with the fit results superimposed. The points represent the data, with the vertical bars giving the corresponding statistical uncertainties. The thick curves are results of the fits, the dash-dotted lines display the signal contributions, and the short-dashed lines show the combinatorial background contributions. The long-dashed line shows the contribution from partially reconstructed BJ/ψK0XBJ/ψK0X decays. The dashed line displays the contribution from swapping K±π±K±π± in the reconstruction.

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Figure 2:
(a) Two-dimensional distribution of mB+KmB+K versus mB+πmB+π in data. (b) The fitted B+πB+π invariant mass distribution. The points represent the data, the thick solid curve is the fit projection, the thin lines indicate the three excited B0B0 signal contributions, the short-dashed curve is the combinatorial background, and the long-dashed lines show the contributions from the excited B0sB0s decays.

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Figure 2-a:
Two-dimensional distribution of mB+KmB+K versus mB+πmB+π in data.

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Figure 2-b:
The fitted B+πB+π invariant mass distribution. The points represent the data, the thick solid curve is the fit projection, the thin lines indicate the three excited B0B0 signal contributions, the short-dashed curve is the combinatorial background, and the long-dashed lines show the contributions from the excited B0sB0s decays.

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Figure 3:
Invariant mass distributions of (a) B+KB+K and (b) B0K0SB0K0S candidates with the results of the fit overlaid. The points represent the data, the thick solid curves are the results of the overall fits, and the thin solid lines display the signal contributions. The short-dashed lines show the combinatorial background contributions. The long-dashed lines show: in (a) the contributions from excited B0B0 meson decays, and in (b) the contributions from swapping K±π±K±π± in the reconstruction of the B0B0 mesons.

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Figure 3-a:
Invariant mass distribution of B0K0SB0K0S candidates with the results of the fit overlaid. The points represent the data, the thick solid curves are the results of the overall fits, and the thin solid lines display the signal contributions. The short-dashed lines show the combinatorial background contributions. The long-dashed lines show the contributions from swapping K±π±K±π± in the reconstruction of the B0B0 mesons.

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Figure 3-b:
Invariant mass distributions of (a) B+KB+K and (b) B0K0SB0K0S candidates with the results of the fit overlaid. The points represent the data, the thick solid curves are the results of the overall fits, and the thin solid lines display the signal contributions. The short-dashed lines show the combinatorial background contributions. The long-dashed lines show: in (a) the contributions from excited B0B0 meson decays, and in (b) the contributions from swapping K±π±K±π± in the reconstruction of the B0B0 mesons.
Tables

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Table 1:
Results on the masses, mass differences, and natural widths of the B()s1,2B()s1,2 mesons from previous measurements. The mass differences are defined as ΔM±Bs1M(Bs1)MPDGB+MPDGKΔM±Bs1M(Bs1)MPDGB+MPDGK and ΔM±Bs2M(Bs2)MPDGB+MPDGKΔM±Bs2M(Bs2)MPDGB+MPDGK, where the PDG superscript refers to the world-average mass values at the time of each publication.

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Table 2:
The observed signal yields (NN), natural widths (ΓΓ), and mass differences from the fits to the mBKmBK distributions in data. The uncertainties are statistical only.

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Table 3:
Relative systematic uncertainties in percent in the ratios R0±2R0±2 and R0±1R0±1.

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Table 4:
Relative systematic uncertainties in percent in the ratios R±2R±2, R02R02, R±σR±σ, and R0σR0σ.

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Table 5:
Systematic uncertainties (in MeV) in the measured mass differences and natural width. The Bs2Bs2 width is measured only in the B+KB+K channel.
Summary
The PP-wave B0sB0s meson states are studied using a data sample corresponding to an integrated luminosity of 19.6 fb11 of proton-proton collisions collected by the CMS experiment at s=s= 8 TeV in 2012. Observation and evidence are reported for the decays Bs2(5840)0B0K0SBs2(5840)0B0K0S and Bs1(5830)0B0K0SBs1(5830)0B0K0S, respectively. Four ratios of branching fractions and two ratios of production cross sections multiplied by the branching fractions of the PP-wave B0sB0s mesons into a B meson and kaon are measured. In addition, the differences between the Bs1,2Bs1,2 mass and the sum of the B meson and kaon mass are determined, as well as the Bs2(5840)0Bs2(5840)0 natural width. Finally, using a new approach, the mass differences MB0MB+MB0MB+ and MB0MB+MB0MB+ are measured, where the latter is determined for the first time.
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