cern.ch

Observation of the annihilation decay mode $B^{0}\to K^{+}K^{-}$

[to restricted-access page]

Abstract

A search for the $B^{0}\to K^{+}K^{-}$ decay is performed using $pp$-collision data collected by LHCb. The data set corresponds to integrated luminosities of 1 and 2 fb$^{-1}$ at center-of-mass energies of 7 and 8 TeV, respectively. This decay is observed for the first time, with a significance of more than five standard deviations. The analysis also results in an improved measurement of the branching fraction for the $B_s^0\to \pi^+\pi^-$ decay. The measured branching fractions are $BR(B^0\to K^+K^-) = (7.80 \pm 1.27 \pm 0.81 \pm 0.21) \times 10^{-8}$ and $BR(B_s^0\to\pi^+\pi^-) = (6.91 \pm 0.54 \pm 0.63 \pm 0.19 \pm 0.40) \times 10^{-7}$. The first uncertainty is statistical, the second is systematic, the third is due to the uncertainty on the $B^0\to K^+\pi^-$ branching fraction used as a normalization. For the $B_s^0$ mode, the fourth accounts for the uncertainty on the ratio of the probabilities for $b$ quarks to hadronize into $B_s^0$ and $B^0$ mesons.

Figures and captions

Dominant Feynman graphs contributing to the $ B ^0 \rightarrow K ^+ K ^- $ and $ B ^0_ s \rightarrow \pi ^+ \pi ^- $ decay amplitudes: (left) penguin-annihilation and (right) $W$-exchange topologies.

Fig1a.pdf [248 KiB]
HiDef png [38 KiB]
Thumbnail [24 KiB]
*.C file
Fig1a.pdf
Fig1b.pdf [246 KiB]
HiDef png [27 KiB]
Thumbnail [16 KiB]
*.C file
Fig1b.pdf

Distributions of (left) $m_{ K ^+ K ^- }$ and (right) $m_{\pi ^+ \pi ^- }$ for candidates passing $S_{ K ^+ K ^- }$ and $S_{\pi ^+ \pi ^- }$, respectively. The continuous (blue) curves represent the results of the best fits to the data points. The most relevant contributions to the invariant mass spectra are shown as indicated in the legends. The vertical scales are chosen to magnify the relevant signal regions. The bin-by-bin differences between the fits and the data, in units of standard deviations, are also shown.

Fig2a.pdf [36 KiB]
HiDef png [307 KiB]
Thumbnail [268 KiB]
*.C file
Fig2a.pdf
Fig2b.pdf [42 KiB]
HiDef png [317 KiB]
Thumbnail [270 KiB]
*.C file
Fig2b.pdf

Log-likelihood ratio as a function of the $ B ^0 \rightarrow K ^+ K ^- $ signal yield. The dashed (red) and continuous (blue) curves correspond to the exclusion and to the inclusion of systematic uncertainties, respectively.

Fig3.pdf [13 KiB]
HiDef png [118 KiB]
Thumbnail [82 KiB]
*.C file
Fig3.pdf

Animated gif made out of all figures.

PAPER-2016-036.gif
Thumbnail
thumbnail_PAPER-2016-036.gif

Tables and captions

Systematic uncertainties on the yields for the $ B ^0 \rightarrow K ^+ K ^- $ and $ B ^0_ s \rightarrow \pi ^+ \pi ^- $ decays.

Table_1.pdf [53 KiB]
HiDef png [52 KiB]
Thumbnail [23 KiB]
tex code
Table_1.pdf

Supplementary Material [file]

Supplementary material full pdf

Supple[..].pdf [488 KiB]
Supplementary.pdf

This ZIP file contains supplemetary material for the publication LHCb-PAPER-2016-036. The files are: Supplementary.pdf : An overview of the extra figures and tables *.pdf, *.png, *.eps *.C : The figures in variuous formats

Fig1a.pdf [38 KiB]
HiDef png [224 KiB]
Thumbnail [202 KiB]
*C file
Fig1a.pdf
Fig1b.pdf [43 KiB]
HiDef png [265 KiB]
Thumbnail [244 KiB]
*C file
Fig1b.pdf
Fig1c.pdf [44 KiB]
HiDef png [264 KiB]
Thumbnail [247 KiB]
*C file
Fig1c.pdf
Fig2a.pdf [41 KiB]
HiDef png [301 KiB]
Thumbnail [266 KiB]
*C file
Fig2a.pdf
Fig2b.pdf [42 KiB]
HiDef png [326 KiB]
Thumbnail [289 KiB]
*C file
Fig2b.pdf
Fig3a.pdf [44 KiB]
HiDef png [241 KiB]
Thumbnail [211 KiB]
*C file
Fig3a.pdf
Fig3b.pdf [43 KiB]
HiDef png [244 KiB]
Thumbnail [220 KiB]
*C file
Fig3b.pdf
Fig3c.pdf [37 KiB]
HiDef png [233 KiB]
Thumbnail [209 KiB]
*C file
Fig3c.pdf
Fig4a.pdf [41 KiB]
HiDef png [293 KiB]
Thumbnail [254 KiB]
*C file
Fig4a.pdf
Fig4b.pdf [41 KiB]
HiDef png [323 KiB]
Thumbnail [280 KiB]
*C file
Fig4b.pdf

Created on 20 February 2021.