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Register a new userThe Pheno-analysis of B-> K(*) mu^+ mu^- decays in 2011 plus
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Gudrun Hiller
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We report on recent developments in the phenomenology of exclusive b -> s mu^+ mu^- decays in testing the standard model and explore its borders: the benefits of the region of large dimuon invariant masses and the exploitation of the angular distributions. Consequences of model-independent analyses from current and future data are pointed out.
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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 $8mathrm{,TeV}$. 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^+rightarrowphi 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 $B^+rightarrow K^+pi^+pi^-mu^{+}mu^{-}$.
The angular distributions of the rare decays $B^+ to K^+mu^+mu^-$ and $B^0 to K^0_{rmscriptscriptstyle S}mu^+mu^-$ are studied with data corresponding to 3$~$fb$^{-1}$ of integrated luminosity, collected in proton-proton collisions at 7 and 8$~$TeV centre-of-mass energies with the LHCb detector. The angular distribution is described by two parameters, $F_{rm H}$ and the forward-backward asymmetry of the dimuon system $A_{rm FB}$, which are determined in bins of the dimuon mass squared. The parameter $F_{rm H}$ is a measure of the contribution from (pseudo)scalar and tensor amplitudes to the decay width. The measurements of $A_{rm FB}$ and $F_{rm H}$ reported here are the most precise to date and are compatible with predictions from the Standard Model.
We analyse the results recently presented on the $B^{+} to K^{*+} mu^+ mu^-$ angular observables by the LHCb Collaboration which show indications for New Physics beyond the Standard Model. Within a model-independent analysis, we compare the fit results with the corresponding results for the angular observables in $B^{0} to K^{*0} mu^+ mu^-$.
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.
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.
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