CMS-PAS-BPH-16-003 | ||
Observation of the B∗s2(5840)0→B0K0S decay and studies of excited B0s mesons in proton-proton collisions at √s= 8 TeV | ||
CMS Collaboration | ||
June 2018 | ||
Abstract: The observation of the B∗s2(5840)0→B0K0S decay is presented and a measurement of its relative branching fraction to the B∗s2(5840)0→B+K− decay using a data sample of 19.6 fb−1 collected with the CMS detector in proton-proton collision at the centre-of-mass energy 8 TeV. The analysis is performed by studying P-wave B0s meson decays into B+K− and B0K0S states, where the ground-state B mesons are identified using the decays B+→J/ψK+ and B0→J/ψK+π−. The masses of P-wave B0s meson states are measured and the natural width of the B∗s2(5840)0 state is determined to be Γ(B∗s2(5840)0)= (1.52 ± 0.34 (stat) ± 0.30 (syst) MeV. The first measurement of the mass difference between the charged and neutral B∗ mesons is also presented. | ||
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These preliminary results are superseded in this paper, EPJC 78 (2018) 939. The superseded preliminary plots can be found here. |
Figures | |
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Figure 1:
Invariant mass distributions of J/ψK+ (a) and J/ψK+π− (b) candidates in the data with the fit results superimposed. |
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Figure 1-a:
Invariant mass distributions of J/ψK+ (a) and J/ψK+π− (b) candidates in the data with the fit results superimposed. |
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Figure 1-b:
Invariant mass distributions of J/ψK+ (a) and J/ψK+π− (b) candidates in the data with the fit results superimposed. |
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Figure 2:
(a) The fitted B+π− invariant mass distribution. The points represent the data, the thick solid curve is the fit projection, the thin lines indicate the excited B0 signal contributions, the dashed curve is the background, and the long-dashed lines show the contributions from the excited B0s decays. (b) Two-dimensional distribution of mB+K− versus mB+π− in data. |
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Figure 2-a:
(a) The fitted B+π− invariant mass distribution. The points represent the data, the thick solid curve is the fit projection, the thin lines indicate the excited B0 signal contributions, the dashed curve is the background, and the long-dashed lines show the contributions from the excited B0s decays. (b) Two-dimensional distribution of mB+K− versus mB+π− in data. |
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Figure 2-b:
(a) The fitted B+π− invariant mass distribution. The points represent the data, the thick solid curve is the fit projection, the thin lines indicate the excited B0 signal contributions, the dashed curve is the background, and the long-dashed lines show the contributions from the excited B0s decays. (b) Two-dimensional distribution of mB+K− versus mB+π− in data. |
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Figure 3:
Invariant mass distributions of B+K− (a) and B0K0S (b) candidates with the results of the fit overlaid. The points represent the data, the thick curves are the fit projections, the thin lines display the signal contributions, and the long-dashed lines show: in (a) the contributions from excited B0 meson decays; in (b) the contributions from K±↔π± swap in B0 reconstruction. The dashed lines show the background contribution. |
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Figure 3-a:
Invariant mass distributions of B+K− (a) and B0K0S (b) candidates with the results of the fit overlaid. The points represent the data, the thick curves are the fit projections, the thin lines display the signal contributions, and the long-dashed lines show: in (a) the contributions from excited B0 meson decays; in (b) the contributions from K±↔π± swap in B0 reconstruction. The dashed lines show the background contribution. |
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Figure 3-b:
Invariant mass distributions of B+K− (a) and B0K0S (b) candidates with the results of the fit overlaid. The points represent the data, the thick curves are the fit projections, the thin lines display the signal contributions, and the long-dashed lines show: in (a) the contributions from excited B0 meson decays; in (b) the contributions from K±↔π± swap in B0 reconstruction. The dashed lines show the background contribution. |
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Figure 4:
mB0 distribution in simulation with the fit result superimposed. (a) signal with matching; (b) reflection from 'K±↔π± swap' obtained by requiring the reconstructed kaon candidate to be matched to the generated pion and vice versa. |
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Figure 4-a:
mB0 distribution in simulation with the fit result superimposed. (a) signal with matching; (b) reflection from 'K±↔π± swap' obtained by requiring the reconstructed kaon candidate to be matched to the generated pion and vice versa. |
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Figure 4-b:
mB0 distribution in simulation with the fit result superimposed. (a) signal with matching; (b) reflection from 'K±↔π± swap' obtained by requiring the reconstructed kaon candidate to be matched to the generated pion and vice versa. |
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Figure 5:
The B+π− invariant mass distributions from the simulated decay: (a) B∗s2→B+K−; (b) B∗s2→B∗+K−; (c) Bs1→B∗+K−. |
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Figure 5-a:
The B+π− invariant mass distributions from the simulated decay: (a) B∗s2→B+K−; (b) B∗s2→B∗+K−; (c) Bs1→B∗+K−. |
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Figure 5-b:
The B+π− invariant mass distributions from the simulated decay: (a) B∗s2→B+K−; (b) B∗s2→B∗+K−; (c) Bs1→B∗+K−. |
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Figure 5-c:
The B+π− invariant mass distributions from the simulated decay: (a) B∗s2→B+K−; (b) B∗s2→B∗+K−; (c) Bs1→B∗+K−. |
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Figure 6:
The B+K− invariant mass distributions from the simulated decay: (a) B∗2→B+π−, (b) B∗2→B∗+π− and (c) B1→B∗+π−. |
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Figure 6-a:
The B+K− invariant mass distributions from the simulated decay: (a) B∗2→B+π−, (b) B∗2→B∗+π− and (c) B1→B∗+π−. |
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Figure 6-b:
The B+K− invariant mass distributions from the simulated decay: (a) B∗2→B+π−, (b) B∗2→B∗+π− and (c) B1→B∗+π−. |
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Figure 6-c:
The B+K− invariant mass distributions from the simulated decay: (a) B∗2→B+π−, (b) B∗2→B∗+π− and (c) B1→B∗+π−. |
Tables | |
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Table 1:
Results on B(∗)s1,2 from previous measurements. Mass differences are designated as ΔM±Bs1≡M(Bs1)−M(B∗+)−M(K−), ΔM±B∗s2≡M(B∗s2)−M(B+)−M(K−). |
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Table 2:
Results from the fits to the mBK distributions in data. |
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Table 3:
Systematic uncertainties in percent in the ratios R0±2 and R0±1. |
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Table 4:
Systematic uncertainties (in%) in the ratios R±2∗, R02∗, R±σ, and R0σ. |
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Table 5:
Systematic uncertainties (in MeV) in the measured mass differences and natural width (ΓB∗s2, measured only in B+K− channel). |
Summary |
In summary, the P-wave B0s meson states are studied using a data sample corresponding to an integrated luminosity of 19.6 fb−1 of pp collisions collected by the CMS experiment at √s= 8 TeV in 2012. The observation and the first evidence are reported for the decays B∗s2→B0K0S and Bs1→B∗0K0S, respectively. Four ratios of branching fractions and two ratios of cross section multiplied by the branching fractions of the P-wave B0s mesons into B meson and kaon are measured. In addition, the differences between the B(∗)s1,2 mass and the sum of B meson and kaon mass are determined, as well as the B(∗)s2 natural width. Finally, using a new approach, the mass differences mB0−mB+ and mB∗0−mB∗+ are measured, where the latter mass difference is measured for the first time. |
References | ||||
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Compact Muon Solenoid LHC, CERN |
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