Measurement of Form-Factor-Independent Observables in the Decay $B^0\to K^{*0}{\mu }^{\mathbf{+}}{\mu }^{\mathbf{-}}$

We present a measurement of form-factor-independent angular observables in the decay $B^0\to K^{*}(892{)}^0{\mu }^{+}{\mu }^{-}$. The analysis is based on a data sample corresponding to an integrated luminosity of $1.0{\mathrm{fb}}^{-1}$, collected by the LHCb experiment in $pp$ collisions at a center-of-mass energy of 7 TeV. Four observables are measured in six bins of the dimuon invariant mass squared $q^2$ in the range $0.1<q^2<19.0{\mathrm{GeV}}^2/c^4$. Agreement with recent theoretical predictions of the standard model is found for 23 of the 24 measurements. A local discrepancy, corresponding to 3.7 Gaussian standard deviations is observed in one $q^2$ bin for one of the observables. Considering the 24 measurements as independent, the probability to observe such a discrepancy, or larger, in one is 0.5%.

Figure 1

Measured values of $P_4^{\prime }$ and $P_5^{\prime }$ (black points) compared with SM predictions from Ref. [10] [gray (blue) bands]. The error bars indicate in each case the 68.3% confidence level.