CMS-BPH-13-009

CMS-BPH-13-009 ; CERN-EP/2016-161
Observation of the decay $\mathrm{B}^+ \to \psi( 2 \mathrm{S} ) \phi(1020) \mathrm{ K }^+$ in pp collisions at $\sqrt{s} = $ 8 TeV
CMS Collaboration
10 July 2016
Phys. Lett. B 764 (2017) 66
Abstract: The decay $\mathrm{B}^+ \to \psi( 2 \mathrm{S} ) \phi(1020) \mathrm{ K }^+$ is observed for the first time using data collected from pp collisions at $\sqrt{s} = $ 8 TeV by the CMS experiment at the LHC, corresponding to an integrated luminosity of 19.6 fb$^{-1}$. The branching fraction of this decay is measured, using the mode $\mathrm{B}^+\to \psi( 2 \mathrm{S} ) \mathrm{ K }^+$ as normalization, to be ( 4.0 $\pm$ 0.4 (stat) $\pm$ 0.6 (syst) $\pm$ 0.2 ($\mathcal{B})$ )$\times$ 10$^{-6}$, where the third uncertainty is from the imprecision in the normalization channel.
Links: e-print arXiv:1607.02638 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: The $\psi( 2 \mathrm{S} ) \phi \mathrm{ K }^+ $ mass distribution after the selection requirements. The solid curve shows the result of fitting this distribution to a signal represented by two Gaussian functions and a first-order polynomial for the background. The shaded area represents the signal component, while the dotted line shows the fitted background contribution.
png pdf	Figure 2: The distributions of the $\mathrm{ K }^+ \mathrm{ K }^- $ invariant mass closest to the nominal $\phi $ mass within (a) and outside (b) the $\mathrm{B}^+ $ mass window. The results show the total fit, as well as the four components: $\phi $ signal, non-$\mathrm{B}^+ $ background, non-$\phi $ signal, and in (b) the Crystal Ball function component of the non-$\mathrm{B}^+ $ background.
png pdf	Figure 2-a: The distributions of the $\mathrm{ K }^+ \mathrm{ K }^- $ invariant mass closest to the nominal $\phi $ mass within (a) and outside (b) the $\mathrm{B}^+ $ mass window. The results show the total fit, as well as the four components: $\phi $ signal, non-$\mathrm{B}^+ $ background, non-$\phi $ signal, and in (b) the Crystal Ball function component of the non-$\mathrm{B}^+ $ background.
png pdf	Figure 2-b: The distributions of the $\mathrm{ K }^+ \mathrm{ K }^- $ invariant mass closest to the nominal $\phi $ mass within (a) and outside (b) the $\mathrm{B}^+ $ mass window. The results show the total fit, as well as the four components: $\phi $ signal, non-$\mathrm{B}^+ $ background, non-$\phi $ signal, and in (b) the Crystal Ball function component of the non-$\mathrm{B}^+ $ background.
png pdf	Figure 3: The $\psi( 2 \mathrm{S} ) \mathrm{ K }^+ $ invariant mass distribution after implementing all the event selection requirements. The solid curve shows the result of fitting this distribution to a signal corresponding to two Gaussian functions and a first-order polynomial for the background. The shaded area represents the contribution from the $\mathrm{B}^+ \to \psi( 2 \mathrm{S} )\mathrm{ K }^+ $ channel, while the dotted line shows the fitted background contribution.
png pdf	Figure 4: The $\psi( 2 \mathrm{S} ) \mathrm{ K }^+ \mathrm{ K }^- \mathrm{ K }^+ $ invariant mass distribution with no $\phi $ mass selection. The solid curve shows the result of fitting this distribution to a signal represented by two Gaussian functions and a second-order polynomial for the background. The shaded area represents the signal component, while the dotted line shows the fitted background contribution.

Tables
png pdf	Table 1: The selection criteria derived from the optimization procedure.
png pdf	Table 2: Relative systematic uncertainties in the measurement of $\mathcal {B}(\mathrm{B}^+ \to \psi( 2 \mathrm{S} ) \phi \mathrm{ K }^+ )$ in percent. The total systematic uncertainty corresponds to the sum in quadrature of the listed uncertainties.

Summary

In summary, the $\mathrm{B}^+\to \psi( 2 \mathrm{S} )\phi \mathrm{ K }^+$ decay has been observed for the first time by the CMS Collaboration. The result has been achieved using data from pp collisions at $\sqrt{s} =$ 8 TeV, corresponding to an integrated luminosity of 19.6 fb$^{-1}$. The branching fraction $\mathcal{B}(\mathrm{B}^+\to \psi( 2 \mathrm{S} )\phi\mathrm{ K }^+)$ is determined to be (4.0 $\pm$ 0.4 (stat) $\pm$ 0.6 (syst) $\pm$ 0.2 ($\mathcal{B}$))$\times$ 10$^{-6}$, where the third uncertainty reflects the imprecision in the value of $\mathcal{B}(\mathrm{B}^+\to \psi( 2 \mathrm{S} )\mathrm{ K }^+)$. The upper limit on the fraction of $\mathrm{B}^+\to \psi( 2 \mathrm{S} ) (\text{non-}\phi)\mathrm{ K }^+$ decays in $\mathrm{B}^+ \to \psi( 2 \mathrm{S} ) \mathrm{ K }^+\mathrm{ K }^+\mathrm{ K }^+$ channel is found to be 0.26 at 95% confidence. The observation of $\mathrm{B}^+\to \psi( 2 \mathrm{S} )\phi \mathrm{ K }^+$ offers future opportunities in searches for resonances in the $\psi( 2 \mathrm{S} )\phi$ mass spectrum.

References
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