CMS-BPH-17-005

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

Figures
png pdf	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.
png pdf	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.
png pdf	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.
png pdf	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.
png pdf	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.
png pdf	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.
png pdf	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.
png pdf	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
png pdf	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
png pdf	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).
png pdf	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].
png pdf	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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