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Register a new userMeasurement of $C!P$ asymmetries in the decays $B^0 rightarrow K^{*0} mu^+ mu^-$ and $B^+ rightarrow K^{+} mu^+ mu^-$
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The direct $C!P$ asymmetries of the decays $B^0 rightarrow K^{*0} mu^+ mu^-$ and $B^+ rightarrow K^{+} mu^+ mu^-$ are measured using $pp$ collision data corresponding to an integrated luminosity of 3.0$mbox{fb}^{-1}$ collected with the LHCb detector. The respective control modes $B^0 rightarrow J/psi K^{*0}$ and $B^+ rightarrow J/psi K^{+}$ are used to account for detection and production asymmetries. The measurements are made in several intervals of $mu^+ mu^-$ invariant mass squared, with the $phi(1020)$ and charmonium resonance regions excluded. Under the hypothesis of zero $C!P$ asymmetry in the control modes, the average values of the asymmetries are begin{align} {cal A}_{C!P}(B^0 rightarrow K^{*0} mu^+ mu^-) &= -0.035 pm 0.024 pm 0.003, cr {cal A}_{C!P}(B^+ rightarrow K^{+} mu^+ mu^-) &= phantom{-}0.012 pm 0.017 pm 0.001, end{align} where the first uncertainties are statistical and the second are due to systematic effects. Both measurements are consistent with the Standard Model prediction of small $C!P$ asymmetry in these decays.
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A measurement of the differential branching fraction of the decay ${B^{0}rightarrow K^{ast}(892)^{0}mu^{+}mu^{-}}$ is presented together with a determination of the S-wave fraction of the $K^+pi^-$ system in the decay $B^{0}rightarrow K^{+}pi^{-}mu^{+}mu^{-}$. The analysis is based on $pp$-collision data corresponding to an integrated luminosity of 3,fb$^{-1}$ collected with the LHCb experiment. The measurements are made in bins of the invariant mass squared of the dimuon system, $q^2$. Precise theoretical predictions for the differential branching fraction of $B^{0}rightarrow K^{ast}(892)^{0}mu^{+}mu^{-}$ decays are available for the $q^2$ region $1.1<q^2<6.0,{rm GeV}^2/c^4$. In this $q^2$ region, for the $K^+pi^-$ invariant mass range $796 < m_{Kpi} < 996,{rm MeV}/c^2$, the S-wave fraction of the $K^+pi^-$ system in $B^{0}rightarrow K^{+}pi^{-}mu^{+}mu^{-}$ decays is found to be begin{equation*} F_{rm S} = 0.101pm0.017({rm stat})pm0.009 ({rm syst}), end{equation*} and the differential branching fraction of $B^{0}rightarrow K^{ast}(892)^{0}mu^{+}mu^{-}$ decays is determined to be begin{equation*} {rm d}mathcal{B}/{rm d} q^2 = (0.342_{,-0.017}^{,+0.017}({rm stat})pm{0.009}({rm syst})pm0.023({rm norm}))times 10^{-7}c^{4}/{rm GeV}^{2}. end{equation*} The differential branching fraction measurements presented are the most precise to date and are found to be in agreement with Standard Model predictions.
A measurement of the $CP$ asymmetry in $B^+ rightarrow K^+ mu^+ mu^-$ decays is presented using $pp$ collision data, corresponding to an integrated luminosity of 1.0${,fb}^{-1}$, recorded by the LHCb experiment during 2011 at a centre-of-mass energy of 7 TeV. The measurement is performed in seven bins of $mu^+ mu^-$ invariant mass squared in the range ${0.05<q^{2}<22.00{mathrm{GeV^2/}c^4}}$, excluding the ${J/psi}$ and $psi{(2S)}$ resonance regions. Production and detection asymmetries are corrected for using the $B^+ rightarrow J/psi K^+$ decay as a control mode. Averaged over all the bins, the $CP$ asymmetry is found to be ${{cal A}_{CP} = 0.000pm 0.033{(stat.)} pm0.005 {(syst.)} pm 0.007{}(J/psi K^+)}$, where the third uncertainty is due to the $CP$ asymmetry of the control mode. This is consistent with the Standard Model prediction.
Transitions of the type $b to s l^+ l^-$ are flavour changing neutral current processes where new physics can enter in competing loop diagrams with respect to the Standard Model contributions. In these decays several observables sensitive to new physics, and where theoretical uncertainties are under control, can be constructed. Particularly interesting are the angular asymmetries in the decay $B_d to K^* mu^+ mu^-$ and the measurement of the branching fraction of the decays $B_{s,d} to mu^+ mu^-$. Recent measurements of these observables and the measurement of the isospin asymmetry in the decays $B to K^{(*)} mu^+ mu^-$ are presented.
A search for the decay $B_{s}^0 rightarrow overline{K}{}^{*0}mu^+mu^-$ is presented using data sets corresponding to 1.0, 2.0 and 1.6 $text{fb}^{-1}$ of integrated luminosity collected during $pp$ collisions with the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, respectively. An excess is found over the background-only hypothesis with a significance of 3.4 standard deviations. The branching fraction of the $B_{s}^0 rightarrow overline{K}{}^{*0}mu^+mu^-$ decay is determined to be $mathcal{B}(B_{s}^0 rightarrow overline{K}{}^{*0}mu^+mu^-) = [2.9 pm 1.0~(text{stat}) pm 0.2~(text{syst}) pm 0.3~(text{norm})] times 10^{-8}$, where the first and second uncertainties are statistical and systematic, respectively. The third uncertainty is due to limited knowledge of external parameters used to normalise the branching fraction measurement.
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