cern.ch

First observations of the rare decays $B^+ \rightarrow K^+\pi^+\pi^-\mu^+\mu^-$ and $B^+ \rightarrow\phi K^+\mu^+\mu^-$

[to restricted-access page]

Information

Tools

Abstract

First observations of the rare decays $B^+\rightarrow K^+\pi^+\pi^-\mu^+\mu^-$ and $B^+\rightarrow \phi K^+\mu^+\mu^-$ are presented using data corresponding to an integrated luminosity of $3.0 {fb}^{-1}$, collected by the LHCb experiment at centre-of-mass energies of $7$ and $8\mathrm{ TeV}$. The branching fractions of the decays are \begin{eqnarray*} \mathcal{B}(B^+\rightarrow K^+\pi^+\pi^-\mu^+\mu^-) &=& (4.36 ^{+0.29}_{-0.27} \mathrm{(stat)}\pm 0.21 \mathrm{(syst)}\pm0.18 \mathrm{(norm)})\times10^{-7},\\ \mathcal{B}(B^+\rightarrow\phi K^+\mu^+\mu^-) &=& (0.82 ^{+0.19}_{-0.17} \mathrm{(stat)} ^{+0.10}_{-0.04} \mathrm{(syst)}\pm0.27 \mathrm{(norm)}) \times10^{-7},\end{eqnarray*} where the uncertainties are statistical, systematic, and due to the uncertainty on the branching fractions of the normalisation modes. A measurement of the differential branching fraction in bins of the invariant mass squared of the dimuon system is also presented for the decay $B^+\rightarrow K^+\pi^+\pi^-\mu^{+}\mu^{-}$.

Figures and captions

Invariant mass of $ B ^+ \rightarrow K ^+ \pi ^+ \pi ^- \mu ^+\mu ^- $ candidates in bins of $q^2$ with fit projections overlaid. The signal component (shaded light blue) is modelled by the sum of two Gaussian functions, each with a power-law tail at low mass. The background component (shaded dark blue) is modelled by an exponential function. In the $q^2$ ranges $4.30< q^2 <8.68$ $ {\mathrm{ Ge V^2 /}c^4}$ , $10.09< q^2 <12.86$ $ {\mathrm{ Ge V^2 /}c^4}$ , and $14.18< q^2 <19.00$ $ {\mathrm{ Ge V^2 /}c^4}$ , scaling factors are applied to account for the vetoes of the radiative tails of the charmonium resonances, resulting in steps in the background mass shape. The lower right plot shows a separate fit to the signal decay integrated over all $q^2$ bins.

 Fig1a.pdf [17 KiB]
HiDef png [214 KiB]
Thumbnail [174 KiB]
*.C file
Fig1a.pdf
Fig1b.pdf [18 KiB]
HiDef png [228 KiB]
Thumbnail [188 KiB]
*.C file
Fig1b.pdf
Fig1c.pdf [19 KiB]
HiDef png [258 KiB]
Thumbnail [208 KiB]
*.C file
Fig1c.pdf
Fig1d.pdf [18 KiB]
HiDef png [235 KiB]
Thumbnail [193 KiB]
*.C file
Fig1d.pdf
Fig1e.pdf [15 KiB]
HiDef png [155 KiB]
Thumbnail [137 KiB]
*.C file
Fig1e.pdf
Fig1f.pdf [20 KiB]
HiDef png [243 KiB]
Thumbnail [199 KiB]
*.C file
Fig1f.pdf

Invariant mass distribution of (a) the control decay $ B ^+ \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^+ \pi ^+ \pi ^- $ and (b) the normalisation mode $ B ^+ \rightarrow \psi {(2S)} K ^+ $ with fit projections overlaid.

 Fig2a.pdf [21 KiB]
HiDef png [232 KiB]
Thumbnail [198 KiB]
*.C file
Fig2a.pdf
Fig2b.pdf [20 KiB]
HiDef png [211 KiB]
Thumbnail [180 KiB]
*.C file
Fig2b.pdf

Differential branching fraction $ {\rm d}\cal B ( B ^+ \rightarrow K ^+ \pi ^+ \pi ^- \mu ^+\mu ^- )/ {\rm d} q^2 $. Errors shown include both statistical and systematic uncertainties. Shaded regions indicate the vetoed charmonium resonances.

 Fig3.pdf [14 KiB]
HiDef png [96 KiB]
Thumbnail [88 KiB]
*.C file
Fig3.pdf

Background-subtracted $m( K ^+ \pi ^+ \pi ^- )$ distributions for (a) the signal decay $ B ^+ \rightarrow K ^+ \pi ^+ \pi ^- \mu ^+\mu ^- $ and (b) the control channel $ B ^+ \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^+ \pi ^+ \pi ^- $. The vertical lines indicate the masses of the $K_1(1270)^+$ and $K_1(1400)^+$ resonances.

 Fig4a.pdf [19 KiB]
HiDef png [177 KiB]
Thumbnail [158 KiB]
*.C file
Fig4a.pdf
Fig4b.pdf [24 KiB]
HiDef png [179 KiB]
Thumbnail [158 KiB]
*.C file
Fig4b.pdf

Invariant $m(\phi K ^+ \mu ^+\mu ^- )$ distributions for (a) $ B ^+ \rightarrow \phi K ^+ \mu ^+\mu ^- $ and (b) $ B ^+ \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \phi K ^+ $ decays with fit projections overlaid.

 Fig5a.pdf [18 KiB]
HiDef png [213 KiB]
Thumbnail [180 KiB]
*.C file
Fig5a.pdf
Fig5b.pdf [20 KiB]
HiDef png [225 KiB]
Thumbnail [184 KiB]
*.C file
Fig5b.pdf

Animated gif made out of all figures.

 PAPER-2014-030.gif
Thumbnail
thumbnail_PAPER-2014-030.gif

Tables and captions

Signal yields for the decay $ B ^+ \rightarrow K ^+ \pi ^+ \pi ^- \mu ^+\mu ^- $ and resulting differential branching fractions in bins of $ q^2$ . The first contribution to the uncertainty is statistical, the second systematic, where the uncertainty due to the branching fraction of the normalisation channel is included. The $q^2$ binning used corresponds to the binning used in previous analyses of $b\rightarrow s\mu ^+ \mu ^- $ decays [1,2,3]. Results are also presented for the $q^2$ range from $1$ to $6 {\mathrm{ Ge V^2 /}c^4} $, where theory predictions are expected to be most reliable.

 Table_1.pdf [60 KiB]
HiDef png [102 KiB]
Thumbnail [52 KiB]
tex code 		Table_1.pdf

Created on 27 April 2024.