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

TL;DR

This paper reports the first observation of two rare B+ meson decays involving muon pairs, measuring their branching fractions and analyzing their differential decay rates using LHCb data at 7 and 8 TeV.

Contribution

The study provides the first experimental measurements of the branching fractions for the decays B+ to K+ pi+ pi- mu+ mu- and B+ to phi K+ mu+ mu-, including differential decay rate analysis.

Findings

First observation of the decays with statistical significance.

Measured branching fractions with statistical, systematic, and normalization uncertainties.

Presented differential branching fraction as a function of dimuon invariant mass squared.

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 $B^+\rightarrow K^+\pi^+\pi^-\mu^{+}\mu^{-}$.