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Register a new userAngular moments of the decay $Lambda_b^0 rightarrow Lambda mu^{+} mu^{-}$ at low hadronic recoil
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An analysis of the angular distribution of the decay $Lambda_b^0 rightarrow Lambda mu^{+} mu^{-}$ is presented, using data collected with the LHCb detector between 2011 and 2016 and corresponding to an integrated luminosity of approximately $5,fb^{-1}$. Angular observables are determined using a moment analysis of the angular distribution at low hadronic recoil, corresponding to the dimuon invariant mass squared range $15 < q^{2} < 20, GeV^2/c^4$. The full basis of observables is measured for the first time. The lepton-side, hadron-side and combined forward-backward asymmetries of the decay are determined to be begin{align} A_{FB}^{l} & = -0.39 pm 0.04,rm{stat} pm 0.01, rm{syst}, onumber A_{FB}^{h} & = -0.30 pm 0.05,rm{stat} pm 0.02, rm{syst}, onumber A_{FB}^{lh} & = +0.25 pm 0.04,rm{stat} pm 0.01, rm{syst}. onumber end{align} The measurements are consistent with Standard Model predictions.
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The suppressed decay $Lambda^{0}_{b}rightarrow ppi^{-}mu^{+}mu^{-}$, excluding the $J/psi$ and $psi(2S)rightarrow mu^{+}mu^{-}$ resonances, is observed for the first time with a significance of 5.5 standard deviations. The analysis is performed with proton-proton collision data corresponding to an integrated luminosity of $3mathrm{fb}^{-1}$ collected with the LHCb experiment. The $Lambda^{0}_{b}rightarrow ppi^{-}mu^{+}mu^{-}$ branching fraction is measured relative to the $Lambda^{0}_{b}rightarrow J/psi(rightarrow mu^{+}mu^{-})ppi^{-}$ branching fraction giving begin{align} onumber frac{mathcal{B}(Lambda^{0}_{b}rightarrow ppi^{-}mu^{+}mu^{-})}{mathcal{B}({Lambda^{0}_{b}rightarrow J/psi(rightarrow mu^{+}mu^{-})ppi^{-}})} &= 0.044pm0.012pm0.007, end{align} where the first uncertainty is statistical and the second is systematic. This is the first observation of a $brightarrow d$ transition in a baryonic decay.
The differential branching fraction of the rare decay $Lambda^{0}_{b} rightarrow Lambda mu^+mu^-$ is measured as a function of $q^{2}$, the square of the dimuon invariant mass. The analysis is performed using proton-proton collision data, corresponding to an integrated luminosity of $3.0 mbox{ fb}^{-1}$, collected by the LHCb experiment. Evidence of signal is observed in the $q^2$ region below the square of the $J/psi$ mass. Integrating over $15 < q^{2} < 20 mbox{ GeV}^2/c^4$ the branching fraction is measured as $dmathcal{B}(Lambda^{0}_{b} rightarrow Lambda mu^+mu^-)/dq^2 = (1.18 ^{+ 0.09} _{-0.08} pm 0.03 pm 0.27) times 10^{-7} ( mbox{GeV}^{2}/c^{4})^{-1}$, where the uncertainties are statistical, systematic and due to the normalisation mode, $Lambda^{0}_{b} rightarrow J/psi Lambda$, respectively. In the $q^2$ intervals where the signal is observed, angular distributions are studied and the forward-backward asymmetries in the dimuon ($A^{l}_{rm FB}$) and hadron ($A^{h}_{rm FB}$) systems are measured for the first time. In the range $15 < q^2 < 20 mbox{ GeV}^2/c^4$ they are found to be $A^{l}_{rm FB} = -0.05 pm 0.09 mbox{ (stat)} pm 0.03 mbox{ (syst)}$ and $A^{h}_{rm FB} = -0.29 pm 0.07 mbox{ (stat)} pm 0.03 mbox{ (syst)}$.
We present an angular analysis of the $B^{+}rightarrow K^{ast+}(rightarrow K_{S}^{0}pi^{+})mu^{+}mu^{-}$ decay using 9$,mbox{fb}^{-1}$ of $pp$ collision data collected with the LHCb experiment. For the first time, the full set of CP-averaged angular observables is measured in intervals of the dimuon invariant mass squared. Local deviations from Standard Model predictions are observed, similar to those in previous LHCb analyses of the isospin-partner $B^{0}rightarrow K^{ast0}mu^{+}mu^{-}$ decay. The global tension is dependent on which effective couplings are considered and on the choice of theory nuisance parameters.
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.
An angular analysis of the $B^{0}rightarrow K^{*0}(rightarrow K^{+}pi^{-})mu^{+}mu^{-}$ decay is presented. The dataset corresponds to an integrated luminosity of $3.0,{mbox{fb}^{-1}}$ of $pp$ collision data collected at the LHCb experiment. The complete angular information from the decay is used to determine $C!P$-averaged observables and $C!P$ asymmetries, taking account of possible contamination from decays with the $K^{+}pi^{-}$ system in an S-wave configuration. The angular observables and their correlations are reported in bins of $q^2$, the invariant mass squared of the dimuon system. The observables are determined both from an unbinned maximum likelihood fit and by using the principal moments of the angular distribution. In addition, by fitting for $q^2$-dependent decay amplitudes in the region $1.1<q^{2}<6.0mathrm{,Gekern -0.1em V}^{2}/c^{4}$, the zero-crossing points of several angular observables are computed. A global fit is performed to the complete set of $C!P$-averaged observables obtained from the maximum likelihood fit. This fit indicates differences with predictions based on the Standard Model at the level of 3.4 standard deviations. These differences could be explained by contributions from physics beyond the Standard Model, or by an unexpectedly large hadronic effect that is not accounted for in the Standard Model predictions.
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