cern.ch

Measurement of the isospin asymmetry in $B \to K^{(*)}\mu^+ \mu^-$ decays

[to restricted-access page]

Information

Tools

Abstract

The isospin asymmetries of $B \to K^{(*)}\mu^+\mu^-$ decays and the partial branching fractions of $B^0 \to K^0\mu^+\mu^-$ and $B^+ \to K^{*+}\mu^+\mu^-$ are measured as a function of the di-muon mass squared $q^2$ using an integrated luminosity of 1.0 fb$^{-1}$ collected with the LHCb detector. The $B \to K\mu^+\mu^-$ isospin asymmetry integrated over $q^2$ is negative, deviating from zero with over 4 $\sigma$ significance. The $B \to K^{*}\mu^+\mu^-$ decay measurements are consistent with the Standard Model prediction of negligible isospin asymmetry. The observation of the decay $B^0 \to K^0_{\rm\scriptscriptstyle S}\mu^+\mu^-$ is reported with 5.7 $\sigma$ significance. Assuming that the branching fraction of $B^0 \to K^0\mu^+\mu^-$ is twice that of $B^0 \to K^0_{\rm\scriptscriptstyle S}\mu^+\mu^-$, the branching fractions of $B^0 \to K^0\mu^+\mu^-$ and $B \to K^{*+}\mu^+\mu^-$ are found to be ($0.31^{+0.07}_{-0.06}) \times 10^{-6}$ and ($1.16\pm0.19) \times 10^{-6}$, respectively.

Figures and captions

Mass of the di-muon versus the mass of the $ B ^+ \rightarrow K ^+ \mu ^+ \mu ^- $ candidates. Only the di-muon mass region close to the $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}$ and $\psi {(2S)}$ masses is shown. The lines show the boundaries of the regions which are removed. Regions (a)--(c) are explained in the text.

bvsjps[..].pdf [48 KiB]
HiDef png [719 KiB]
Thumbnail [402 KiB]
*.C file
bvsjpsi_lines.pdf

Mass distributions and fits of the signal channels integrated over the full $ q^{2}$ region. For the $ K ^0_{\rm\scriptscriptstyle S}$ channels, the plots are shown separately for the L and D $ K ^0_{\rm\scriptscriptstyle S}$ reconstruction categories, (a,b) and (c,d) respectively. The signal component is shown by the dashed line, the partially reconstructed component in 2(a) and 2(c) is shown by the dotted line while the solid line shows the entire fit model.

ksmumu_LL.pdf [19 KiB]
HiDef png [236 KiB]
Thumbnail [186 KiB]
*.C file
ksmumu_LL.pdf
bukst_LL.pdf [18 KiB]
HiDef png [202 KiB]
Thumbnail [172 KiB]
*.C file
bukst_LL.pdf
ksmumu_DD.pdf [21 KiB]
HiDef png [252 KiB]
Thumbnail [206 KiB]
*.C file
ksmumu_DD.pdf
bukst_DD.pdf [19 KiB]
HiDef png [236 KiB]
Thumbnail [197 KiB]
*.C file
bukst_DD.pdf
kmumu.pdf [21 KiB]
HiDef png [234 KiB]
Thumbnail [192 KiB]
*.C file
kmumu.pdf
kstmumu.pdf [21 KiB]
HiDef png [227 KiB]
Thumbnail [182 KiB]
*.C file
kstmumu.pdf

Efficiency of the $ K ^0_{\rm\scriptscriptstyle S}$ channels with respect to the $ K ^+$ channels for (left) $ B \rightarrow K \mu ^+ \mu ^- $ and (right) $ B \rightarrow K^{*} \mu ^+ \mu ^- $ , calculated using the simulation. The efficiencies are shown for both L and D $ K ^0_{\rm\scriptscriptstyle S}$ reconstruction categories and include the visible branching fraction of $ K ^0 \rightarrow K ^0_{\rm\scriptscriptstyle S} \rightarrow \pi ^+ \pi ^- $. The error bars are not visible as they are smaller than the marker size.

kmumu_eff.pdf [13 KiB]
HiDef png [137 KiB]
Thumbnail [117 KiB]
*.C file
kmumu_eff.pdf
kstmum[..].pdf [13 KiB]
HiDef png [135 KiB]
Thumbnail [114 KiB]
*.C file
kstmumu_eff.pdf

Differential branching fractions of (left) $ B ^0 \rightarrow K ^0 \mu ^+ \mu ^- $ and (right) $ B ^+ \rightarrow K^{*+} \mu ^+ \mu ^- $ . The theoretical SM predictions are taken from Refs. [23,24].

ksmumu_BF.pdf [18 KiB]
HiDef png [138 KiB]
Thumbnail [132 KiB]
*.C file
ksmumu_BF.pdf
bukst_BF.pdf [18 KiB]
HiDef png [151 KiB]
Thumbnail [144 KiB]
*.C file
bukst_BF.pdf

Isospin asymmetry of (left) $ B \rightarrow K \mu ^+ \mu ^- $ and (right) $ B \rightarrow K^{*} \mu ^+ \mu ^- $ . For $ B \rightarrow K^{*} \mu ^+ \mu ^- $ the theoretical SM prediction, which is very close to zero, is shown for $ q^{2}$ below 8.68 $ {\mathrm{ Ge V /}c^2}$ , from Ref. [25].

kmumu_AI.pdf [14 KiB]
HiDef png [68 KiB]
Thumbnail [40 KiB]
*.C file
kmumu_AI.pdf
kstmumu_AI.pdf [16 KiB]
HiDef png [123 KiB]
Thumbnail [126 KiB]
*.C file
kstmumu_AI.pdf

Animated gif made out of all figures.

PAPER-2012-011.gif
Thumbnail
thumbnail_PAPER-2012-011.gif

Tables and captions

Signal yields of the $ B \rightarrow K^{(*)} \mu ^+ \mu ^- $ decays. The upper bound of the highest $ q^{2}$ bin, $ q^{2} _{\mathrm{max}}$, is 19.3 $ {\mathrm{ Ge V^2 /}c^4}$ and 23.0 $ {\mathrm{ Ge V^2 /}c^4}$ for $ B \rightarrow K^{*} \mu ^+ \mu ^- $ and $ B \rightarrow K \mu ^+ \mu ^- $ , respectively.

Table_1.pdf [53 KiB]
HiDef png [77 KiB]
Thumbnail [38 KiB]
tex code
Table_1.pdf

Partial branching fractions of $ B ^0 \rightarrow K ^0 \mu ^+ \mu ^- $ and isospin asymmetries of $ B \rightarrow K \mu ^+ \mu ^- $ decays. The significance of the deviation of $ A_{\rm I}$ from zero is shown in the last column. The errors include the statistical and systematic uncertainties.

Table_2.pdf [53 KiB]
HiDef png [63 KiB]
Thumbnail [30 KiB]
tex code
Table_2.pdf

Partial branching fractions of $ B ^+ \rightarrow K^{*+} \mu ^+ \mu ^- $ and isospin asymmetries of $ B \rightarrow K^{*} \mu ^+ \mu ^- $ decays. The significance of the deviation of $ A_{\rm I}$ from zero is shown in the last column. The errors include the statistical and systematic uncertainties.

Table_3.pdf [53 KiB]
HiDef png [62 KiB]
Thumbnail [30 KiB]
tex code
Table_3.pdf

Supplementary Material [file]

Supplementary material full pdf

supple[..].pdf [440 KiB]
supplementary.pdf

This ZIP file contains supplemetary material for the publication LHCb-PAPER-2012-011. The files are: Supplementary.pdf : An overview of the extra figures *.pdf, *.png, *.eps : The figures in variuous formats

Fig1a-S.pdf [16 KiB]
HiDef png [182 KiB]
Thumbnail [137 KiB]
*C file
Fig1a-S.pdf
Fig1b-S.pdf [17 KiB]
HiDef png [185 KiB]
Thumbnail [140 KiB]
*C file
Fig1b-S.pdf
Fig1c-S.pdf [17 KiB]
HiDef png [184 KiB]
Thumbnail [143 KiB]
*C file
Fig1c-S.pdf
Fig1d-S.pdf [16 KiB]
HiDef png [174 KiB]
Thumbnail [136 KiB]
*C file
Fig1d-S.pdf
Fig1e-S.pdf [16 KiB]
HiDef png [163 KiB]
Thumbnail [132 KiB]
*C file
Fig1e-S.pdf
Fig1f-S.pdf [16 KiB]
HiDef png [173 KiB]
Thumbnail [132 KiB]
*C file
Fig1f-S.pdf
Fig2a-S.pdf [17 KiB]
HiDef png [187 KiB]
Thumbnail [139 KiB]
*C file
Fig2a-S.pdf
Fig2b-S.pdf [17 KiB]
HiDef png [198 KiB]
Thumbnail [151 KiB]
*C file
Fig2b-S.pdf
Fig2c-S.pdf [19 KiB]
HiDef png [230 KiB]
Thumbnail [177 KiB]
*C file
Fig2c-S.pdf
Fig2d-S.pdf [18 KiB]
HiDef png [208 KiB]
Thumbnail [158 KiB]
*C file
Fig2d-S.pdf
Fig2e-S.pdf [17 KiB]
HiDef png [183 KiB]
Thumbnail [139 KiB]
*C file
Fig2e-S.pdf
Fig2f-S.pdf [17 KiB]
HiDef png [198 KiB]
Thumbnail [148 KiB]
*C file
Fig2f-S.pdf
Fig3a-S.pdf [16 KiB]
HiDef png [153 KiB]
Thumbnail [129 KiB]
*C file
Fig3a-S.pdf
Fig3b-S.pdf [16 KiB]
HiDef png [163 KiB]
Thumbnail [134 KiB]
*C file
Fig3b-S.pdf
Fig3c-S.pdf [16 KiB]
HiDef png [148 KiB]
Thumbnail [124 KiB]
*C file
Fig3c-S.pdf
Fig3d-S.pdf [16 KiB]
HiDef png [154 KiB]
Thumbnail [131 KiB]
*C file
Fig3d-S.pdf
Fig3e-S.pdf [15 KiB]
HiDef png [138 KiB]
Thumbnail [118 KiB]
*C file
Fig3e-S.pdf
Fig3f-S.pdf [15 KiB]
HiDef png [138 KiB]
Thumbnail [119 KiB]
*C file
Fig3f-S.pdf
Fig4a-S.pdf [17 KiB]
HiDef png [182 KiB]
Thumbnail [148 KiB]
*C file
Fig4a-S.pdf
Fig4b-S.pdf [17 KiB]
HiDef png [177 KiB]
Thumbnail [146 KiB]
*C file
Fig4b-S.pdf
Fig4c-S.pdf [18 KiB]
HiDef png [187 KiB]
Thumbnail [160 KiB]
*C file
Fig4c-S.pdf
Fig4d-S.pdf [17 KiB]
HiDef png [177 KiB]
Thumbnail [150 KiB]
*C file
Fig4d-S.pdf
Fig4e-S.pdf [16 KiB]
HiDef png [142 KiB]
Thumbnail [120 KiB]
*C file
Fig4e-S.pdf
Fig4f-S.pdf [16 KiB]
HiDef png [160 KiB]
Thumbnail [134 KiB]
*C file
Fig4f-S.pdf

Created on 11 July 2020.