Abstract
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.
Highlights
The LHCb detector [12] is a single-arm forward spectrometer covering the pseudorapidity range 2 < η < 5, designed for the study of particles containing b or c quarks
The direct CP asymmetries of the decays B0 → K∗0μ+μ− and B+ → K+μ+μ− are measured using pp collision data corresponding to an integrated luminosity of 3.0 fb−1 collected with the LHCb detector
Under the hypothesis of zero CP asymmetry in the control modes, the average values of the asymmetries are ACP (B0 → K∗0μ+μ−) = −0.035 ± 0.024 ± 0.003, ACP (B+ → K+μ+μ−) = 0.012 ± 0.017 ± 0.001, where the first uncertainties are statistical and the second are due to systematic effects
Summary
The LHCb detector [12] is a single-arm forward spectrometer covering the pseudorapidity range 2 < η < 5, designed for the study of particles containing b or c quarks. Decays of hadronic particles are described by EvtGen [20], in which final-state radiation is generated using Photos [21]. The interaction of the generated particles with the detector and its response are implemented using the Geant toolkit [22, 23] as described in ref. The simulated samples are reweighted to model more accurately the data distributions in variables used in the analysis. These include the pT of the B meson, the number of tracks in the event, and the χ2 of the vertex fit to the final-state tracks, which may differ due to misalignments of the detector and mismodelling of the material description in the VELO region. The B+ → K+μ+μ− samples are reweighted for the pT of the decay products
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