CMS-PAS-BPH-16-003

CMS-PAS-BPH-16-003
Observation of the $\mathrm{B}^{*}_{\mathrm{s}2}(5840)^0\rightarrow\mathrm{B}^0\mathrm{K}^0_{\mathrm{S}}$ decay and studies of excited $\mathrm{B}^0_\mathrm{s}$ mesons in proton-proton collisions at $\sqrt{s}=$ 8 TeV
CMS Collaboration
June 2018

Abstract: The observation of the $\mathrm{B}^{}_{\mathrm{s}2}(5840)^0\rightarrow\mathrm{B}^0\mathrm{K}^0_{\mathrm{S}}$ decay is presented and a measurement of its relative branching fraction to the $\mathrm{B}^{}_{\mathrm{s}2}(5840)^0\rightarrow\mathrm{B}^+\mathrm{K}^{-}$ 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 $\mathrm{B}^{0}_\mathrm{s}$ meson decays into $\mathrm{B}^+\mathrm{K}^-$ and $\mathrm{B}^0 \mathrm{K}^0_{\mathrm{S}}$ states, where the ground-state $\mathrm{B}$ mesons are identified using the decays $\mathrm{B}^+ \rightarrow \mathrm{J}/\psi\mathrm{K}^+$ and $\mathrm{B}^0 \rightarrow \mathrm{J}/\psi\mathrm{K}^+ \pi^-$ . The masses of P-wave $\mathrm{B}^0_\mathrm{s}$ meson states are measured and the natural width of the $\mathrm{B}^{}_{\mathrm{s}2}(5840)^0$ state is determined to be $\Gamma(\mathrm{B}^{}_{\mathrm{s}2}(5840)^0)=$ (1.52 $\pm$ 0.34 (stat) $\pm$ 0.30 (syst) MeV. The first measurement of the mass difference between the charged and neutral $\mathrm{B}^*$ mesons is also presented.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; These preliminary results are superseded in this paper, EPJC 78 (2018) 939. The superseded preliminary plots can be found here.

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Invariant mass distributions of ${\mathrm {J} / \psi} {{{\mathrm {K}}} ^+}$ (a) and ${\mathrm {J} / \psi} {{{\mathrm {K}}} ^+} {{\pi} ^-}$ (b) candidates in the data with the fit results superimposed.
png pdf	Figure 1-a: Invariant mass distributions of ${\mathrm {J} / \psi} {{{\mathrm {K}}} ^+}$ (a) and ${\mathrm {J} / \psi} {{{\mathrm {K}}} ^+} {{\pi} ^-}$ (b) candidates in the data with the fit results superimposed.
png pdf	Figure 1-b: Invariant mass distributions of ${\mathrm {J} / \psi} {{{\mathrm {K}}} ^+}$ (a) and ${\mathrm {J} / \psi} {{{\mathrm {K}}} ^+} {{\pi} ^-}$ (b) candidates in the data with the fit results superimposed.
png pdf	Figure 2: (a) The fitted ${{{\mathrm {B}} ^+} {{\pi} ^-}}$ invariant mass distribution. The points represent the data, the thick solid curve is the fit projection, the thin lines indicate the excited ${{\mathrm {B}} ^0}$ signal contributions, the dashed curve is the background, and the long-dashed lines show the contributions from the excited ${{\mathrm {B}} ^0_ {\mathrm {s}}}$ decays. (b) Two-dimensional distribution of ${m_{{{{\mathrm {B}} ^+}} {{{\mathrm {K}}} ^-}}}$ versus ${m_{{{{\mathrm {B}} ^+}} {{\pi} ^-}}}$ in data.
png pdf	Figure 2-a: (a) The fitted ${{{\mathrm {B}} ^+} {{\pi} ^-}}$ invariant mass distribution. The points represent the data, the thick solid curve is the fit projection, the thin lines indicate the excited ${{\mathrm {B}} ^0}$ signal contributions, the dashed curve is the background, and the long-dashed lines show the contributions from the excited ${{\mathrm {B}} ^0_ {\mathrm {s}}}$ decays. (b) Two-dimensional distribution of ${m_{{{{\mathrm {B}} ^+}} {{{\mathrm {K}}} ^-}}}$ versus ${m_{{{{\mathrm {B}} ^+}} {{\pi} ^-}}}$ in data.
png pdf	Figure 2-b: (a) The fitted ${{{\mathrm {B}} ^+} {{\pi} ^-}}$ invariant mass distribution. The points represent the data, the thick solid curve is the fit projection, the thin lines indicate the excited ${{\mathrm {B}} ^0}$ signal contributions, the dashed curve is the background, and the long-dashed lines show the contributions from the excited ${{\mathrm {B}} ^0_ {\mathrm {s}}}$ decays. (b) Two-dimensional distribution of ${m_{{{{\mathrm {B}} ^+}} {{{\mathrm {K}}} ^-}}}$ versus ${m_{{{{\mathrm {B}} ^+}} {{\pi} ^-}}}$ in data.
png pdf	Figure 3: Invariant mass distributions of ${{{\mathrm {B}} ^+} {{{\mathrm {K}}} ^-}}$ (a) and ${{{\mathrm {B}} ^0} {{{\mathrm {K}}} ^0_{\rm {S}}}}$ (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 ${{\mathrm {B}} ^0}$ meson decays; in (b) the contributions from ${{{\mathrm {K}}} ^\pm} \leftrightarrow {{\pi} ^\pm}$ swap in ${{\mathrm {B}} ^0}$ reconstruction. The dashed lines show the background contribution.
png pdf	Figure 3-a: Invariant mass distributions of ${{{\mathrm {B}} ^+} {{{\mathrm {K}}} ^-}}$ (a) and ${{{\mathrm {B}} ^0} {{{\mathrm {K}}} ^0_{\rm {S}}}}$ (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 ${{\mathrm {B}} ^0}$ meson decays; in (b) the contributions from ${{{\mathrm {K}}} ^\pm} \leftrightarrow {{\pi} ^\pm}$ swap in ${{\mathrm {B}} ^0}$ reconstruction. The dashed lines show the background contribution.
png pdf	Figure 3-b: Invariant mass distributions of ${{{\mathrm {B}} ^+} {{{\mathrm {K}}} ^-}}$ (a) and ${{{\mathrm {B}} ^0} {{{\mathrm {K}}} ^0_{\rm {S}}}}$ (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 ${{\mathrm {B}} ^0}$ meson decays; in (b) the contributions from ${{{\mathrm {K}}} ^\pm} \leftrightarrow {{\pi} ^\pm}$ swap in ${{\mathrm {B}} ^0}$ reconstruction. The dashed lines show the background contribution.
png pdf	Figure 4: ${m_{{{\mathrm {B}} ^0}}}$ distribution in simulation with the fit result superimposed. (a) signal with matching; (b) reflection from ' ${{{\mathrm {K}}} ^\pm} \leftrightarrow {{\pi} ^\pm}$ swap' obtained by requiring the reconstructed kaon candidate to be matched to the generated pion and vice versa.
png pdf	Figure 4-a: ${m_{{{\mathrm {B}} ^0}}}$ distribution in simulation with the fit result superimposed. (a) signal with matching; (b) reflection from ' ${{{\mathrm {K}}} ^\pm} \leftrightarrow {{\pi} ^\pm}$ swap' obtained by requiring the reconstructed kaon candidate to be matched to the generated pion and vice versa.
png pdf	Figure 4-b: ${m_{{{\mathrm {B}} ^0}}}$ distribution in simulation with the fit result superimposed. (a) signal with matching; (b) reflection from ' ${{{\mathrm {K}}} ^\pm} \leftrightarrow {{\pi} ^\pm}$ swap' obtained by requiring the reconstructed kaon candidate to be matched to the generated pion and vice versa.
png pdf	Figure 5: The ${{{\mathrm {B}} ^+} {{\pi} ^-}}$ invariant mass distributions from the simulated decay: (a) ${{{\mathrm {B}} ^{}_{{\mathrm {s}} 2}} \to {{\mathrm {B}} ^+} {{{\mathrm {K}}} ^-}}$ ; (b) ${{{\mathrm {B}} ^{}_{{\mathrm {s}} 2}} \to {{\mathrm {B}} ^{+}} {{{\mathrm {K}}} ^-}}$ ; (c) ${{\mathrm {B}} _{{\mathrm {s}} 1}} \to {{\mathrm {B}} ^{+}} {{{\mathrm {K}}} ^-}$ .
png pdf	Figure 5-a: The ${{{\mathrm {B}} ^+} {{\pi} ^-}}$ invariant mass distributions from the simulated decay: (a) ${{{\mathrm {B}} ^{}_{{\mathrm {s}} 2}} \to {{\mathrm {B}} ^+} {{{\mathrm {K}}} ^-}}$ ; (b) ${{{\mathrm {B}} ^{}_{{\mathrm {s}} 2}} \to {{\mathrm {B}} ^{+}} {{{\mathrm {K}}} ^-}}$ ; (c) ${{\mathrm {B}} _{{\mathrm {s}} 1}} \to {{\mathrm {B}} ^{+}} {{{\mathrm {K}}} ^-}$ .
png pdf	Figure 5-b: The ${{{\mathrm {B}} ^+} {{\pi} ^-}}$ invariant mass distributions from the simulated decay: (a) ${{{\mathrm {B}} ^{}_{{\mathrm {s}} 2}} \to {{\mathrm {B}} ^+} {{{\mathrm {K}}} ^-}}$ ; (b) ${{{\mathrm {B}} ^{}_{{\mathrm {s}} 2}} \to {{\mathrm {B}} ^{+}} {{{\mathrm {K}}} ^-}}$ ; (c) ${{\mathrm {B}} _{{\mathrm {s}} 1}} \to {{\mathrm {B}} ^{+}} {{{\mathrm {K}}} ^-}$ .
png pdf	Figure 5-c: The ${{{\mathrm {B}} ^+} {{\pi} ^-}}$ invariant mass distributions from the simulated decay: (a) ${{{\mathrm {B}} ^{}_{{\mathrm {s}} 2}} \to {{\mathrm {B}} ^+} {{{\mathrm {K}}} ^-}}$ ; (b) ${{{\mathrm {B}} ^{}_{{\mathrm {s}} 2}} \to {{\mathrm {B}} ^{+}} {{{\mathrm {K}}} ^-}}$ ; (c) ${{\mathrm {B}} _{{\mathrm {s}} 1}} \to {{\mathrm {B}} ^{+}} {{{\mathrm {K}}} ^-}$ .
png pdf	Figure 6: The ${{{\mathrm {B}} ^+} {{{\mathrm {K}}} ^-}}$ invariant mass distributions from the simulated decay: (a) ${{\mathrm {B}} ^{}_{2}} \to {{\mathrm {B}} ^+} {{\pi} ^-}$ , (b) ${{\mathrm {B}} ^{}_{2}} \to {{\mathrm {B}} ^{+}} {{\pi} ^-}$ and (c) ${{\mathrm {B}} _{1}} \to {{\mathrm {B}} ^{+}} {{\pi} ^-}$ .
png pdf	Figure 6-a: The ${{{\mathrm {B}} ^+} {{{\mathrm {K}}} ^-}}$ invariant mass distributions from the simulated decay: (a) ${{\mathrm {B}} ^{}_{2}} \to {{\mathrm {B}} ^+} {{\pi} ^-}$ , (b) ${{\mathrm {B}} ^{}_{2}} \to {{\mathrm {B}} ^{+}} {{\pi} ^-}$ and (c) ${{\mathrm {B}} _{1}} \to {{\mathrm {B}} ^{+}} {{\pi} ^-}$ .
png pdf	Figure 6-b: The ${{{\mathrm {B}} ^+} {{{\mathrm {K}}} ^-}}$ invariant mass distributions from the simulated decay: (a) ${{\mathrm {B}} ^{}_{2}} \to {{\mathrm {B}} ^+} {{\pi} ^-}$ , (b) ${{\mathrm {B}} ^{}_{2}} \to {{\mathrm {B}} ^{+}} {{\pi} ^-}$ and (c) ${{\mathrm {B}} _{1}} \to {{\mathrm {B}} ^{+}} {{\pi} ^-}$ .
png pdf	Figure 6-c: The ${{{\mathrm {B}} ^+} {{{\mathrm {K}}} ^-}}$ invariant mass distributions from the simulated decay: (a) ${{\mathrm {B}} ^{}_{2}} \to {{\mathrm {B}} ^+} {{\pi} ^-}$ , (b) ${{\mathrm {B}} ^{}_{2}} \to {{\mathrm {B}} ^{+}} {{\pi} ^-}$ and (c) ${{\mathrm {B}} _{1}} \to {{\mathrm {B}} ^{+}} {{\pi} ^-}$ .

Tables
png pdf	Table 1: Results on ${{\mathrm {B}} ^{()}_{{\mathrm {s}} 1,2}}$ from previous measurements. Mass differences are designated as ${\Delta M_{{{\mathrm {B}} _{{\mathrm {s}} 1}}}^{\pm}} \equiv {M({{\mathrm {B}} _{{\mathrm {s}} 1}})-M({{\mathrm {B}} ^{+}})-M({{{\mathrm {K}}} ^-})}$ , ${\Delta M_{{{\mathrm {B}} ^{}_{{\mathrm {s}} 2}}}^{\pm}} \equiv {M({{\mathrm {B}} ^{}_{{\mathrm {s}} 2}})-M({{\mathrm {B}} ^+})-M({{{\mathrm {K}}} ^-})}$ .
png pdf	Table 2: Results from the fits to the ${m_{{{\mathrm {B}} {{\mathrm {K}}}}}}$ distributions in data.
png pdf	Table 3: Systematic uncertainties in percent in the ratios ${R^{0\pm}_{2}}$ and ${R^{0\pm}_{1}}$ .
png pdf	Table 4: Systematic uncertainties (in%) in the ratios ${R^{\pm}_{2}}$ , ${R^{0}_{2}}$ , ${R^{\pm}_{\sigma}}$ , and ${R^{0}_{\sigma}}$ .
png pdf	Table 5: Systematic uncertainties (in MeV) in the measured mass differences and natural width ( ${\Gamma _{{{\mathrm {B}} ^{*}_{{\mathrm {s}} 2}}}}$ , measured only in ${{{\mathrm {B}} ^+} {{{\mathrm {K}}} ^-}}$ channel).

Summary

In summary, the P-wave

$\mathrm{B}^{0}_\mathrm{s}$ 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

$\sqrt{s} =$ 8 TeV in 2012. The observation and the first evidence are reported for the decays

$\mathrm{B}^{*}_{\mathrm{s}2}\rightarrow\mathrm{B}^0\mathrm{K}^0_{\mathrm{S}}$ and

$\mathrm{B}_{\mathrm{s}1}\rightarrow\mathrm{B}^{*0}\mathrm{K}^0_{\mathrm{S}}$ , respectively. Four ratios of branching fractions and two ratios of cross section multiplied by the branching fractions of the P-wave

$\mathrm{B}^{0}_\mathrm{s}$ mesons into B meson and kaon are measured. In addition, the differences between the

${\mathrm{B}^{(*)}_{\mathrm{s}1,2}}$ mass and the sum of B meson and kaon mass are determined, as well as the

${\mathrm{B}^{(*)}_{\mathrm{s}2}}$ natural width. Finally, using a new approach, the mass differences

$m_{\mathrm{B}^0}-m_{\mathrm{B}^+}$ and

$m_{\mathrm{B}^{*0}}-m_{\mathrm{B}^{*+}}$ are measured, where the latter mass difference is measured for the first time.

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