cern.ch

Observation of the decay $\overline{B_s^0} \rightarrow \chi_{c2} K^+ K^- $ in the $\phi$ mass region

[to restricted-access page]

Information

Tools

Contact

Abstract

The $\overline{B_s^0} \rightarrow \chi_{c2} K^+ K^- $ decay mode is observed and its branching fraction relative to the corresponding $\chi_{c1}$ decay mode, in a $\pm 15 \textrm{MeV}/c^2$ window around the $\phi$ mass, is found to be $\frac{\mathcal{B}(\overline{B_s^0} \rightarrow \chi_{c2} K^+ K^-) }{ \mathcal{B}(\overline{B_s^0} \rightarrow \chi_{c1} K^+ K^-)} = (17.1 \pm 3.1 \pm 0.4 \pm 0.9)\%,$ where the first uncertainty is statistical, the second systematic and the third due to the knowledge of the branching fractions of radiative $\chi_c$ decays. The decay mode $\overline{B_s^0} \rightarrow \chi_{c1} K^+ K^- $ allows the $ B_s^0$ mass to be measured as $m(B_s^0) = 5366.83 \pm 0.25 \pm 0.27 \, \textrm{MeV}/c^2,$ where the first uncertainty is statistical and the second systematic. A combination of this result with other LHCb determinations of the $B_s^0$ mass is made.

Figures and captions

Tree-level Feynman diagram for the $\overline{ B }{} {}^0_ s \rightarrow \chi_{cJ} \phi$ decay mode.

fig1.pdf [78 KiB]
HiDef png [31 KiB]
Thumbnail [5 KiB]
*.C file
fig1.pdf

Invariant-mass distributions of (left) $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \gamma$ and (right) $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \gamma K^+ K^-$ after the loose selection criteria.

fig2a.pdf [11 KiB]
HiDef png [83 KiB]
Thumbnail [19 KiB]
*.C file
fig2a.pdf
fig2b.pdf [11 KiB]
HiDef png [86 KiB]
Thumbnail [20 KiB] *.C file
fig2b.pdf

MLP response for (solid yellow) the $\overline{ B }{} {}^0_ s \rightarrow \chi _{ c 1} K^+ K^-$ simulation sample, (hashed blue) high-mass sideband and (black points) the background subtracted $\overline{ B }{} {}^0_ s \rightarrow \chi _{ c 1} K^+ K^-$ signal in data. The histogram areas are normalized to the number of $\overline{ B }{} {}^0_ s \rightarrow \chi _{ c 1} K^+ K^-$ candidates observed in data after the loose selection. The arrow indicates the selected threshold.

fig3.pdf [9 KiB]
HiDef png [304 KiB]
Thumbnail [65 KiB]
*.C file
fig3.pdf

Invariant-mass distributions of selected candidates for (left) the $\chi _{ c 1} K^+ K^-$ fit and (right) the $\chi _{ c 2} K^+ K^-$ fit. The total fitted function is superimposed (solid red line) together with the (blue hashed area) $\chi _{ c 1} $ component, (solid yellow) $\chi _{ c 2} $ component and (dashed black line) the background component. The pull, i.e. the difference between the observed and fitted value divided by the uncertainty, is shown below each of the plots.

fig4a.pdf [13 KiB]
HiDef png [276 KiB]
Thumbnail [78 KiB]
*.C file
fig4a.pdf
fig4b.pdf [12 KiB]
HiDef png [362 KiB]
Thumbnail [95 KiB] *.C file
fig4b.pdf

Invariant-mass distribution of the $K^+K^-$ pair for the (left) $\overline{ B }{} {}^0_ s \rightarrow \chi _{ c 1} K^+ K^-$ decay obtained with the $\chi _{ c 1} $ mass constraint applied to the $ B ^0_ s $ candidate invariant mass and (right) $\overline{ B }{} {}^0_ s \rightarrow \chi _{ c 2} K^+ K^-$ decay obtained with the $\chi _{ c 2} $ mass constraint applied to the $ B ^0_ s $ candidate invariant mass. The (red solid line) total fitted function is superimposed together with (blue hashed area) the S-wave component.

fig5a.pdf [14 KiB]
HiDef png [225 KiB]
Thumbnail [69 KiB]
*.C file
fig5a.pdf
fig5b.pdf [13 KiB]
HiDef png [167 KiB]
Thumbnail [63 KiB] *.C file
fig5b.pdf

Animated gif made out of all figures.

PAPER-2018-018.gif
Thumbnail
thumbnail_PAPER-2018-018.gif

Tables and captions

Results of the $\chi _{ c 1} K^+ K^-$ and $\chi _{ c 2} K^+ K^-$ fits to the invariant-mass distributions. A Gaussian constraint is applied to the $s_f$ parameter.

Table_1.pdf [62 KiB]
HiDef png [74 KiB]
Thumbnail [12 KiB]
tex code
Table_1.pdf

Systematic uncertainties for the measurement of the ratio $\mathcal{B}(\overline{ B }{} {}^0_ s \rightarrow \chi _{ c 2} K^+ K^-)/\mathcal{B}(\overline{ B }{} {}^0_ s \rightarrow \chi _{ c 1} K^+ K^-)$.

Table_2.pdf [55 KiB]
HiDef png [60 KiB]
Thumbnail [8 KiB]
tex code
Table_2.pdf

Systematic uncertainties on the $ B ^0_ s $ mass measurement.

Table_3.pdf [37 KiB]
HiDef png [79 KiB]
Thumbnail [11 KiB]
tex code
Table_3.pdf

Supplementary Material [file]

Supplementary material full pdf

supple[..].pdf [195 KiB]
supplementary.pdf

This ZIP file contains supplemetary material for the publication LHCb-PAPER-2018-018. The files are: Supplementary.pdf : An overview of the extra figures *.pdf, *.png, *.eps : The figures in variuous formats

fig6a.pdf [13 KiB]
HiDef png [98 KiB]
Thumbnail [22 KiB]
*C file
fig6a.pdf
fig6b.pdf [13 KiB]
HiDef png [109 KiB]
Thumbnail [26 KiB]
*C file
fig6b.pdf
fig7.pdf [10 KiB]
HiDef png [99 KiB]
Thumbnail [29 KiB]
*C file
fig7.pdf
fig8.pdf [10 KiB]
HiDef png [93 KiB]
Thumbnail [29 KiB]
*C file
fig8.pdf

Created on 09 December 2018.Citation count from INSPIRE on 18 December 2018.