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| CMS-BPH-17-005 ; CERN-EP-2020-070 | ||
| Observation of the $\mathrm{B_{s}^{0} \to \mathrm{X}(3872)\phi}$ decay | ||
| CMS Collaboration | ||
| 10 May 2020 | ||
| Phys. Rev. Lett. 125 (2020) 152001 | ||
| Abstract: Using a data sample of proton-proton collisions at $\sqrt{s} = $ 13 TeV, corresponding to an integrated luminosity of 140 fb$^{-1}$ collected by the CMS experiment in 2016-2018, the $\mathrm{B_{s}^{0} \to \mathrm{X}(3872)\phi}$ decay is observed. Decays into $\mathrm{J/\psi}\pi^{+}\pi^{-}$ and $\mathrm{K^{+}K^{-}}$ are used to reconstruct, respectively, the $\mathrm{X(3872)}$ and $\phi$. The ratio of the product of branching fractions $\mathcal{B}(\mathrm{B_{s}^{0} \to \mathrm{X}(3872)\phi})\,\mathcal{B}(\mathrm{\mathrm{X}(3872)} \to \mathrm{J/\psi}\pi^{+}\pi^{-} )$ to the product $\mathcal{B}(\mathrm{B_{s}^{0} \to \psi(2S)\phi})\,\mathcal{B}(\mathrm{\psi(2S)} \to \mathrm{J/\psi}\pi^{+}\pi^{-} )$ is measured to be (2.21 $\pm$ 0.29 (stat) $\pm$ 0.17 (syst))%. The ratio $\mathcal{B}(\mathrm{B_{s}^{0} \to \mathrm{X}(3872)\phi})/\mathcal{B}(\mathrm{B^{0} \to \mathrm{X}(3872) K^{0}})$ is found to be consistent with one, while the ratio $\mathcal{B}(\mathrm{B_{s}^{0} \to \mathrm{X}(3872)\phi})/\mathcal{B}(\mathrm{B^{+} \to \mathrm{X}(3872) K^{+}})$ is two times smaller. This suggests a difference in the production dynamics of the $\mathrm{X(3872)}$ in $\mathrm{B^{0}}$ and $\mathrm{B_{s}^{0}}$ meson decays compared to $\mathrm{B^{+}}$. The reported observation may shed new light on the nature of the $\mathrm{X(3872)}$ particle. | ||
| Links: e-print arXiv:2005.04764 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ; | ||
| Figures & Tables | Summary | Additional Figures | References | CMS Publications |
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| Figures | |
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Figure 1:
The observed $\mathrm{J/\psi}\pi^{+}\pi^{-}$ (left) and ${\mathrm{K^{+}} \mathrm{K^{-}}}$ (right) invariant mass distributions for the ${\mathrm{B_{s}^{0}} \to \psi(\text{2S})\phi}$ candidates are shown by the points, with the vertical bars representing the statistical uncertainties. The projections of the 2D fit and its various components are shown by the lines. |
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Figure 1-a:
The observed $\mathrm{J/\psi}\pi^{+}\pi^{-}$ invariant mass distribution for the ${\mathrm{B_{s}^{0}} \to \psi(\text{2S})\phi}$ candidates is shown by the points, with the vertical bars representing the statistical uncertainties. The projections of the 2D fit and its various components are shown by the lines. |
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Figure 1-b:
The observed ${\mathrm{K^{+}} \mathrm{K^{-}}}$ invariant mass distribution for the ${\mathrm{B_{s}^{0}} \to \psi(\text{2S})\phi}$ candidates is shown by the points, with the vertical bars representing the statistical uncertainties. The projections of the 2D fit and its various components are shown by the lines. |
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Figure 2:
The observed $\mathrm{J/\psi}\pi^{+}\pi^{-}$ (left) and ${\mathrm{K^{+}} \mathrm{K^{-}}}$ (right) invariant mass distributions for the ${\mathrm{B_{s}^{0}} \to \mathrm{X(3872)} \phi}$ candidates are shown by the points, with the vertical bars representing the statistical uncertainties. The projections of the 2D fit and its various components are shown by the lines. |
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Figure 2-a:
The observed $\mathrm{J/\psi}\pi^{+}\pi^{-}$ invariant mass distribution for the ${\mathrm{B_{s}^{0}} \to \mathrm{X(3872)} \phi}$ candidates is shown by the points, with the vertical bars representing the statistical uncertainties. The projections of the 2D fit and its various components are shown by the lines. |
png pdf |
Figure 2-b:
The observed ${\mathrm{K^{+}} \mathrm{K^{-}}}$ invariant mass distribution for the ${\mathrm{B_{s}^{0}} \to \mathrm{X(3872)} \phi}$ candidates is shown by the points, with the vertical bars representing the statistical uncertainties. The projections of the 2D fit and its various components are shown by the lines. |
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Figure 3:
Background-subtracted $\psi(\text{2S})\phi $ (left) and $\mathrm{X(3872)} \phi $ (right) invariant mass distributions obtained by ${{}_{s}\mathcal {P}\mathrm {lot}}$ weighting. The result of each fit and its components are shown by the lines. |
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Figure 3-a:
Background-subtracted $\psi(\text{2S})\phi $ invariant mass distribution obtained by ${{}_{s}\mathcal {P}\mathrm {lot}}$ weighting. The result of each fit and its components are shown by the lines. |
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Figure 3-b:
Background-subtracted $\mathrm{X(3872)} \phi $ invariant mass distribution obtained by ${{}_{s}\mathcal {P}\mathrm {lot}}$ weighting. The result of each fit and its components are shown by the lines. |
| Tables | |
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Table 1:
Relative systematic uncertainties in the ratio $R$. |
| Summary |
| In summary, using a data sample corresponding to an integrated luminosity of 140 fb$^{-1}$ of proton-proton collisions collected by the CMS experiment at $\sqrt{s}= $ 13 TeV in 2016--2018, the $\mathrm{B_{s}^{0} \to X(3872)\phi}$ decay is observed for the first time. The comparison with similar decays of $\mathrm{B^{0}}$ and $\mathrm{B^{+}}$ mesons indicates that the $\mathrm{X(3872)}$ formation in B meson decays is different from $\psi(\text{2S})$ formation, suggesting that $\mathrm{X(3872)}$ is not a pure charmonium state and supporting similar conclusions derived from other experimental measurements [2, 5, 8–12]. This observation may shed new light on the nature of the $\mathrm{X(3872)}$ particle. |
| Additional Figures | |
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Additional Figure 1:
The observed $ {\mathrm {J}/\psi} \, {\pi ^{+}} {\pi ^{-}} $ invariant mass distribution for the selected $ {\mathrm {B}^0_\mathrm {s}} \to {\psi \mathrm {(2S)}}\, \phi$ candidates in three ranges of $m({\mathrm {K^{+}}} {\mathrm {K^{-}}})$: (a) left $\phi$ sideband, (b) $\phi$ signal region, (c) right $\phi$ sideband. The projections of the two dimensional fit and its various components are shown by the lines explained in the legend in (b). |
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Additional Figure 1-a:
The observed $ {\mathrm {J}/\psi} \, {\pi ^{+}} {\pi ^{-}} $ invariant mass distribution for the selected $ {\mathrm {B}^0_\mathrm {s}} \to {\psi \mathrm {(2S)}}\, \phi$ candidates in three ranges of $m({\mathrm {K^{+}}} {\mathrm {K^{-}}})$: left $\phi$ sideband. |
png pdf |
Additional Figure 1-b:
The observed $ {\mathrm {J}/\psi} \, {\pi ^{+}} {\pi ^{-}} $ invariant mass distribution for the selected $ {\mathrm {B}^0_\mathrm {s}} \to {\psi \mathrm {(2S)}}\, \phi$ candidates in three ranges of $m({\mathrm {K^{+}}} {\mathrm {K^{-}}})$: $\phi$ signal region. The projection of the two dimensional fit and its various components are shown by the lines explained in the legend. |
png pdf |
Additional Figure 1-c:
The observed $ {\mathrm {J}/\psi} \, {\pi ^{+}} {\pi ^{-}} $ invariant mass distribution for the selected $ {\mathrm {B}^0_\mathrm {s}} \to {\psi \mathrm {(2S)}}\, \phi$ candidates in three ranges of $m({\mathrm {K^{+}}} {\mathrm {K^{-}}})$: right $\phi$ sideband. |
png pdf |
Additional Figure 2:
The observed $ {\mathrm {K^{+}}} {\mathrm {K^{-}}}$ invariant mass distribution for the selected $ {\mathrm {B}^0_\mathrm {s}} \to {\psi \mathrm {(2S)}}\, \phi$ candidates in three ranges of $m({\mathrm {J}/\psi} \, {\pi ^{+}} {\pi ^{-}})$: (a) left ${\psi \mathrm {(2S)}}$ sideband, (b) ${\psi \mathrm {(2S)}}$ signal region, (c) right ${\psi \mathrm {(2S)}}$ sideband. The projections of the two dimensional fit and its various components are shown by the lines explained in the legend in (b). |
png pdf |
Additional Figure 2-a:
The observed $ {\mathrm {K^{+}}} {\mathrm {K^{-}}}$ invariant mass distribution for the selected $ {\mathrm {B}^0_\mathrm {s}} \to {\psi \mathrm {(2S)}}\, \phi$ candidates in three ranges of $m({\mathrm {J}/\psi} \, {\pi ^{+}} {\pi ^{-}})$: left ${\psi \mathrm {(2S)}}$ sideband. |
png pdf |
Additional Figure 2-b:
The observed $ {\mathrm {K^{+}}} {\mathrm {K^{-}}}$ invariant mass distribution for the selected $ {\mathrm {B}^0_\mathrm {s}} \to {\psi \mathrm {(2S)}}\, \phi$ candidates in three ranges of $m({\mathrm {J}/\psi} \, {\pi ^{+}} {\pi ^{-}})$: ${\psi \mathrm {(2S)}}$ signal region. The projection of the two dimensional fit and its various components are shown by the lines explained in the legend. |
png pdf |
Additional Figure 2-c:
The observed $ {\mathrm {K^{+}}} {\mathrm {K^{-}}}$ invariant mass distribution for the selected $ {\mathrm {B}^0_\mathrm {s}} \to {\psi \mathrm {(2S)}}\, \phi$ candidates in three ranges of $m({\mathrm {J}/\psi} \, {\pi ^{+}} {\pi ^{-}})$: right ${\psi \mathrm {(2S)}}$ sideband. |
png pdf |
Additional Figure 3:
The observed $ {\mathrm {J}/\psi} \, {\pi ^{+}} {\pi ^{-}} $ invariant mass distribution for the selected $ {\mathrm {B}^0_\mathrm {s}} \to \mathrm {X}(3872)\, \phi$ candidates in three ranges of $m({\mathrm {K^{+}}} {\mathrm {K^{-}}})$: (a) left $\phi$ sideband, (b) $\phi$ signal region, (c) right $\phi$ sideband. The projections of the two dimensional fit and its various components are shown by the lines explained in the legend in (b). |
png pdf |
Additional Figure 3-a:
The observed $ {\mathrm {J}/\psi} \, {\pi ^{+}} {\pi ^{-}} $ invariant mass distribution for the selected $ {\mathrm {B}^0_\mathrm {s}} \to \mathrm {X}(3872)\, \phi$ candidates in three ranges of $m({\mathrm {K^{+}}} {\mathrm {K^{-}}})$: left $\phi$ sideband. |
png pdf |
Additional Figure 3-b:
The observed $ {\mathrm {J}/\psi} \, {\pi ^{+}} {\pi ^{-}} $ invariant mass distribution for the selected $ {\mathrm {B}^0_\mathrm {s}} \to \mathrm {X}(3872)\, \phi$ candidates in three ranges of $m({\mathrm {K^{+}}} {\mathrm {K^{-}}})$: $\phi$ signal region. right $\phi$ sideband. The projection of the two dimensional fit and its various components are shown by the lines explained in the legend. |
png pdf |
Additional Figure 3-c:
The observed $ {\mathrm {J}/\psi} \, {\pi ^{+}} {\pi ^{-}} $ invariant mass distribution for the selected $ {\mathrm {B}^0_\mathrm {s}} \to \mathrm {X}(3872)\, \phi$ candidates in three ranges of $m({\mathrm {K^{+}}} {\mathrm {K^{-}}})$: right $\phi$ sideband. |
png pdf |
Additional Figure 4:
The observed $ {\mathrm {K^{+}}} {\mathrm {K^{-}}}$ invariant mass distribution for the selected $ {\mathrm {B}^0_\mathrm {s}} \to \mathrm {X}(3872)\, \phi$ candidates in three ranges of $m({\mathrm {J}/\psi} \, {\pi ^{+}} {\pi ^{-}})$: (a) left $\mathrm {X}$ sideband, (b) $\mathrm {X}$ signal region, (c) right $\mathrm {X}$ sideband. The projections of the two dimensional fit and its various components are shown by the lines explained in the legend in (b). |
png pdf |
Additional Figure 4-a:
The observed $ {\mathrm {K^{+}}} {\mathrm {K^{-}}}$ invariant mass distribution for the selected $ {\mathrm {B}^0_\mathrm {s}} \to \mathrm {X}(3872)\, \phi$ candidates in three ranges of $m({\mathrm {J}/\psi} \, {\pi ^{+}} {\pi ^{-}})$: left $\mathrm {X}$ sideband. |
png pdf |
Additional Figure 4-b:
The observed $ {\mathrm {K^{+}}} {\mathrm {K^{-}}}$ invariant mass distribution for the selected $ {\mathrm {B}^0_\mathrm {s}} \to \mathrm {X}(3872)\, \phi$ candidates in three ranges of $m({\mathrm {J}/\psi} \, {\pi ^{+}} {\pi ^{-}})$: $\mathrm {X}$ signal region. The projection of the two dimensional fit and its various components are shown by the lines explained in the legend. |
png pdf |
Additional Figure 4-c:
The observed $ {\mathrm {K^{+}}} {\mathrm {K^{-}}}$ invariant mass distribution for the selected $ {\mathrm {B}^0_\mathrm {s}} \to \mathrm {X}(3872)\, \phi$ candidates in three ranges of $m({\mathrm {J}/\psi} \, {\pi ^{+}} {\pi ^{-}})$: right $\mathrm {X}$ sideband. |
png pdf |
Additional Figure 5:
Comparison of the branching fractions $\mathcal {B}({{\mathrm {B}}}\to {\mathrm {J}/\psi}\, \mathrm {h})$ for ${{\mathrm {B}^{+}}}$, ${{\mathrm {B}^0}}$, and ${\mathrm {B}^0_\mathrm {s}}$ decays. The values are taken from Ref. [4]. |
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Additional Figure 6:
Comparison of the branching fractions $\mathcal {B}({{\mathrm {B}}}\to {\psi \mathrm {(2S)}}\, \mathrm {h})$ for ${{\mathrm {B}^{+}}}$, ${{\mathrm {B}^0}}$, and ${\mathrm {B}^0_\mathrm {s}}$ decays. The values are taken from Ref. [4]. |
png pdf |
Additional Figure 7:
Comparison of the branching fraction products $\mathcal {B}({{\mathrm {B}}}\to \mathrm {X}(3872)\, \mathrm {h})\times \mathcal {B}(\mathrm {X}(3872)\to {\mathrm {J}/\psi} \, {\pi ^{+}} {\pi ^{-}})$ for ${{\mathrm {B}^{+}}}$, ${{\mathrm {B}^0}}$ [4], and ${\mathrm {B}^0_\mathrm {s}}$ decays, where the last result by CMS is highlighted in red. |
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