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| CMS-BPH-16-002 ; CERN-EP-2017-287 | ||
| Search for the X(5568) state decaying into $\mathrm{B}^{0}_{\mathrm{s}}\pi^{\pm}$ in proton-proton collisions at $\sqrt{s} = $ 8 TeV | ||
| CMS Collaboration | ||
| 17 December 2017 | ||
| Phys. Rev. Lett. 120 (2018) 202005 | ||
| Abstract: A search for resonance-like structures in the $\mathrm{B}^{0}_{\mathrm{s}}\pi^{\pm}$ invariant mass spectrum is performed using proton-proton collision data collected by the CMS experiment at the LHC at $\sqrt{s} = $ 8 TeV, corresponding to an integrated luminosity of 19.7 fb$^{-1}$. The $\mathrm{B}^{0}_{\mathrm{s}}$ mesons are reconstructed in the decay chain $\mathrm{B}^{0}_{\mathrm{s}} \rightarrow \mathrm{J}/\psi\,\phi$, with $\mathrm{J}/\psi \rightarrow \mu^+\mu^-$ and $\phi\rightarrow\mathrm{K^{+}}\mathrm{K^{-}}$. The $\mathrm{B}^{0}_{\mathrm{s}}\pi^{\pm}$ invariant mass distribution shows no statistically significant peaks for different selection requirements on the reconstructed $\mathrm{B}^{0}_{\mathrm{s}}$ and $\pi^{\pm}$ candidates. Upper limits are set on the relative production rates of the X(5568) and $\mathrm{B}^{0}_{\mathrm{s}}$ states times the branching fraction of the decay $\mathrm{X}(5568)^{\pm} \rightarrow \mathrm{B}^{0}_{\mathrm{s}} \pi^{\pm} $. In addition, upper limits are obtained as a function of the mass and the natural width of possible exotic states decaying into $\mathrm{B}^{0}_{\mathrm{s}}\pi^{\pm}$. | ||
| Links: e-print arXiv:1712.06144 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ; | ||
| Figures | |
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Figure 1:
Invariant mass distribution of the $ {\mathrm {B}^0_\mathrm {s}} $ candidates with the fit result superimposed. The outermost pairs of dark vertical arrows define the lower and upper $ {\mathrm {B}^0_\mathrm {s}} $ sidebands, while the innermost light vertical arrows delimit the signal region. |
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Figure 2:
(a) The $M^{\Delta}({\mathrm {B}^0_\mathrm {s}} {\pi ^\mathrm {{\pm}}})$ distribution for events in the $ {\mathrm {B}^0_\mathrm {s}} $ signal (points) and sideband regions (bands). The latter is normalized to the former. The vertical band indicates the region $m_{{\mathrm {X}}}\pm \Gamma _{{\mathrm {X}}}$. (b) The $M^{\Delta}({\mathrm {B}^0_\mathrm {s}} {\pi ^\mathrm {{\pm}}})$ distribution for events in the $ {\mathrm {B}^0_\mathrm {s}} $ signal (points) and lower and higher sideband regions (bands), when the requirement on $ M({\mathrm {K^+}} {\mathrm {K^-}}) $ is removed (see text for additional requirements). The three distributions are normalized from the mass threshold up to 5.74 GeV. The excess observed for events in the $ {\mathrm {B}^0_\mathrm {s}} $ signal and higher sideband regions is due to $ {{\mathrm {B}}}^{(*)}_{1,2}{}^+\to {\mathrm {B}^{*0}} {\pi ^+}$ decays. |
png pdf |
Figure 2-a:
The $M^{\Delta}({\mathrm {B}^0_\mathrm {s}} {\pi ^\mathrm {{\pm}}})$ distribution for events in the $ {\mathrm {B}^0_\mathrm {s}} $ signal (points) and sideband regions (bands). The latter is normalized to the former. The vertical band indicates the region $m_{{\mathrm {X}}}\pm \Gamma _{{\mathrm {X}}}$. |
png pdf |
Figure 2-b:
The $M^{\Delta}({\mathrm {B}^0_\mathrm {s}} {\pi ^\mathrm {{\pm}}})$ distribution for events in the $ {\mathrm {B}^0_\mathrm {s}} $ signal (points) and lower and higher sideband regions (bands), when the requirement on $ M({\mathrm {K^+}} {\mathrm {K^-}}) $ is removed (see text for additional requirements). The three distributions are normalized from the mass threshold up to 5.74 GeV. The excess observed for events in the $ {\mathrm {B}^0_\mathrm {s}} $ signal and higher sideband regions is due to $ {{\mathrm {B}}}^{(*)}_{1,2}{}^+\to {\mathrm {B}^{*0}} {\pi ^+}$ decays. |
png pdf |
Figure 3:
The $M^{\Delta}({\mathrm {B}^0_\mathrm {s}} {\pi ^\mathrm {{\pm}}})$ distribution for events in the $ {\mathrm {B}^0_\mathrm {s}} $ signal region with the result of the fit superimposed for the baseline selection with $ {p_{\mathrm {T}}} ({\mathrm {B}^0_\mathrm {s}}) > $ 10 GeV (a) and $ {p_{\mathrm {T}}} ({\mathrm {B}^0_\mathrm {s}}) > $ 15 GeV (b). The vertical band indicates the region $m_{{\mathrm {X}}}\pm \Gamma _{{\mathrm {X}}}$. The lower panels display the pull (difference between the data and the fit result, divided by the statistical uncertainty in the data). |
png pdf |
Figure 3-a:
The $M^{\Delta}({\mathrm {B}^0_\mathrm {s}} {\pi ^\mathrm {{\pm}}})$ distribution for events in the $ {\mathrm {B}^0_\mathrm {s}} $ signal region with the result of the fit superimposed for the baseline selection with $ {p_{\mathrm {T}}} ({\mathrm {B}^0_\mathrm {s}}) > $ 10 GeV. The vertical band indicates the region $m_{{\mathrm {X}}}\pm \Gamma _{{\mathrm {X}}}$. The lower panels display the pull (difference between the data and the fit result, divided by the statistical uncertainty in the data). |
png pdf |
Figure 3-b:
The $M^{\Delta}({\mathrm {B}^0_\mathrm {s}} {\pi ^\mathrm {{\pm}}})$ distribution for events in the $ {\mathrm {B}^0_\mathrm {s}} $ signal region with the result of the fit superimposed for the baseline selection with $ {p_{\mathrm {T}}} ({\mathrm {B}^0_\mathrm {s}}) > $ 15 GeV. The vertical band indicates the region $m_{{\mathrm {X}}}\pm \Gamma _{{\mathrm {X}}}$. The lower panels display the pull (difference between the data and the fit result, divided by the statistical uncertainty in the data). |
png pdf |
Figure 4:
The 95% CL upper limit (UL) on $\rho _{{\mathrm {X}}}$, Eq.(1), as a function of the mass of a possible exotic state decaying into $ {\mathrm {B}^0_\mathrm {s}} {\pi ^\mathrm {{\pm}}}$ for five different values of the natural width of the state. |
png pdf |
Figure 5:
The $M^{\Delta}({\mathrm {B}^0_\mathrm {s}} {\pi ^\mathrm {{\pm}}})$ distributions for events in the $ {\mathrm {B}^0_\mathrm {s}} $ (a) signal and (b) sideband regions for different $\Delta R$ requirements. The uncertainties are not shown for the sake of clarity. The vertical band indicates the region $m_{{\mathrm {X}}}\pm \Gamma _{{\mathrm {X}}}$. |
png pdf |
Figure 5-a:
The $M^{\Delta}({\mathrm {B}^0_\mathrm {s}} {\pi ^\mathrm {{\pm}}})$ distributions for events in the $ {\mathrm {B}^0_\mathrm {s}} $ signal region for different $\Delta R$ requirements. The uncertainties are not shown for the sake of clarity. The vertical band indicates the region $m_{{\mathrm {X}}}\pm \Gamma _{{\mathrm {X}}}$. |
png pdf |
Figure 5-b:
The $M^{\Delta}({\mathrm {B}^0_\mathrm {s}} {\pi ^\mathrm {{\pm}}})$ distributions for events in the $ {\mathrm {B}^0_\mathrm {s}} $ sideband region for different $\Delta R$ requirements. The uncertainties are not shown for the sake of clarity. The vertical band indicates the region $m_{{\mathrm {X}}}\pm \Gamma _{{\mathrm {X}}}$. |
| Summary |
|
In summary, a search for the X(5568) state is performed by the CMS Collaboration using pp collision data collected at $\sqrt{s} = $ 8 TeV and corresponding to an integrated luminosity of 19.7 fb$^{-1}$. With about 50 000 $\mathrm{B}^{0}_{\mathrm{s}}$ signal candidates, no significant structure in the $\mathrm{B}^{0}_{\mathrm{s}}\pi^{\pm}$ invariant mass spectrum is found around the mass reported by the D0 Collaboration (nor for masses up to 5.9 GeV). The absence of a peak is supported by direct comparison with the events in the $\mathrm{B}^{0}_{\mathrm{s}}$ sidebands, and by fits to the $\mathrm{B}^{0}_{\mathrm{s}}\pi^{\pm}$ invariant mass distribution with a resonant component included, using different kinematic selection requirements, as well as variants of the background modeling, fit regions, and quality criteria. Upper limits on the relative production rates of the X(5568) and $\mathrm{B}^{0}_{\mathrm{s}}$ states, multiplied by the unknown branching fraction of the $\mathrm{X}(5568)^{\pm}\to\mathrm{B}^{0}_{\mathrm{s}}\pi^{\pm}$ decay, are computed to be: $\rho_{\mathrm{X}} < $ 1.0% at 95% CL for $ p_{\mathrm{T}}(\mathrm{B}^{0}_{\mathrm{s}})> $ 15 GeV. The upper limits on $\rho_{\mathrm{X}}$ presented in this Letter are a factor of two more stringent than the previous best limits, and do not confirm the existence of the X(5568) state. Additionally, upper limits are set for different values of mass and natural width of a hypothetical exotic resonance decaying into $\mathrm{B}^{0}_{\mathrm{s}}\pi^{\pm}$. |
| References | ||||
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