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Register a new userDirect determination of Wilson coefficients using $B^0to K^{*0}mu^+mu^-$ decays
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A method to directly determine the Wilson coefficients for rare $bto s$ transitions using $B^0to K^{*0}mu^+mu^-$ decays in an unbinned maximum likelihood fit is presented. The method has several advantages compared to the conventional determination of the Wilson coefficients from angular observables that are determined in bins of $q^2$, the square of the mass of the dimuon system. The method uses all experimental information in an optimal way and automatically accounts for experimental correlations. Performing pseudoexperiments, we show the improved sensitivity of the proposed method for the Wilson coefficients. We also demonstrate that it will be possible to use the method with the combined Run 1 and 2 data sample taken by the LHCb experiment.
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We perform an analysis within the Standard Model of $B^{0,+} to K^{*0,+} mu^+ mu^-$ decays in light of the recent measurements from the LHCb experiment, showing that new data strengthen the need for sizable hadronic contributions and correlations among them. We then extend our analysis to New Physics via the Standard Model Effective Theory, and carry out a state-of-the-art fit of available $b to s ell^+ ell^-$ data, including possible hadronic contributions. We find the case of a fully left-handed operator standing out as the simplest scenario with a significance of almost $6sigma$.
Following updated and extended measurements of the full angular distribution of the decay $Lambda_bto Lambda(to p,pi^-)mu^+mu^-$ by the LHCb collaborations, as well as a new measurement of the $Lambda to p pi^-$ decay asymmetry parameter by the BESIII collaboration, we study the impact of these results on searches for non-standard effects in exclusive $bto smu^+mu^-$ decays. To this end, we constrain the Wilson coefficients $mathcal{C}_{9}$ and $mathcal{C}_{10}$ of the numerically leading dimension-six operators in the weak effective Hamiltonian, in addition to the relevant nuisance parameters. In stark contrast to previous analyses of this decay mode, the changes in the updated experimental results lead us to find very good compatibility with both the Standard Model and with the $bto smu^+mu^-$ anomalies observed in rare $B$-meson decays. We provide a detailed analysis of the impact of the partial angular distribution, the full angular distribution, and the $Lambda_bto Lambdamu^+mu^-$ branching fraction on the Wilson coefficients. In this process, we are also able to constrain the size of the production polarization of the $Lambda_b$ baryon at LHCb.
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.
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 $B^{0} to K^{*0} mu^+ mu^-$.
A method for determining the $q^2$ dependent $bar{K}^{*0}$ spin amplitudes of $bar{B}^{0}to bar{K}^{*0}mu^+mu^-$ decays through a maximum likelihood fit to data is presented. While current experimental techniques extract a limited set of observables in bins of $q^2$, our approach allows for the determination of all observable quantities as continuous distributions in $q^2$. By doing this, the method eliminates the need to correct theory predictions of these observables for $q^2$ averaging effects, thus increasing the sensitivity to the effects of physics beyond the Standard Model. Accounting for the symmetries of the angular distribution and using a three parameter ansatz for the $q^2$ dependence of the amplitudes, the precision of the angular observables and the sensitivity to new physics is estimated using simulated events. These studies are based on the sample sizes collected by the LHCb experiment during Run-I and expected for Run-II.
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