Search for the $X(4140)$ state in $B^+\to J/\psi\phi K^+$ decays

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A search for the X(4140) state in B+ to J/psi phi K+ decays is performed with 0.37 fb-1 of pp collisions at sqrt(s)=7 TeV collected by the LHCb experiment. No evidence for this state is found, in 2.4 sigma disagreement with a measurement by CDF. An upper limit on its production rate is set, BR(B+ to X(4140) K+) BR(X(4140) to J/psi phi) / BR(B+ to J/psi phi K+) < 0.07 at 90 confidence level.

Figures and captions

Mass distribution for $B^+\rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \phi K^+$ candidates in the data after the $\pm15$ MeV $\phi$ mass requirement. The fit of a Gaussian signal with a quadratic background (dashed line) is superimposed (solid red line).

figx_j[..].pdf [15 KiB]
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Invariant $M(K^+K^-)$ mass distribution selecting $B^+\rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K^+K^-K^+$ events in the $\pm2.5 \sigma$ region around the $B^+$ mass peak. The dashed line shows the two-body phase-space contribution. The small blue dotted $\phi$ peak on top of it illustrates the amount of the background $\phi$ mesons estimated from the fit to the $B^+$ mass near-sidebands.

figx_k[..].pdf [18 KiB]
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Distribution of the mass difference $M( { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \phi)-M( { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} )$ for the $B^+\rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \phi K^+$ in the $B^+$ ($\pm2.5 \sigma$) and $\phi$ ($\pm15$ MeV) mass windows. Fit of $X(4140)$ signal on top of a smooth background is superimposed (solid red line). The dashed blue (dotted blue) line on top illustrates the expected $X(4140)$ ($X(4274)$) signal yield from the CDF measurement [2]. The top and bottom plots differ by the background function (dashed black line) used in the fit: (a) an efficiency-corrected three-body phase-space (${\cal F}^{\rm bkg}_1$); (b) a quadratic function multiplied by the efficiency-corrected three-body phase-space factor (${\cal F}^{\rm bkg}_2$). The fit ranges are 1030--1400 and 1020--1400 MeV, respectively.

figx_j[..].pdf [40 KiB]
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Efficiency dependence on $M( { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \phi)-M( { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} )$ as determined from the simulation (points with error bars). The efficiency is normalized with respect to the efficiency of the $\phi$ signal fit to the $B^+\rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \phi K^+$ events distributed according to the phase-space model. A cubic polynomial was fitted to the simulated data (superimposed).

figx_e[..].pdf [14 KiB]
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*.C file

Animated gif made out of all figures.


Created on 19 February 2021.