Abstract
Measurements of the differential branching fraction and angular moments of the decay $B^0 \to K^+ \pi^- \mu^+ \mu^-$ in the $K^+\pi^-$ invariant mass range $1330<m(K^+ \pi^-)<1530~MeV/c^2$ are presented. Proton-proton collision data are used, corresponding to an integrated luminosity of 3 $fb^{-1}$ collected by the LHCb experiment. Differential branching fraction measurements are reported in five bins of the invariant mass squared of the dimuon system, $q^2$, between 0.1 and 8.0 $GeV^2/c^4$. For the first time, an angular analysis sensitive to the S-, P- and D-wave contributions of this rare decay is performed. The set of 40 normalised angular moments describing the decay is presented for the $q^2$ range 1.1--6.0 $GeV^2/c^4$.
Highlights
Angular distributionThe final state of the decay B0 → K+π−μ+μ− is fully described by five kinematic variables: three decay angles (θ , θK, φ), m(K+π−), and q2
Of the theory uncertainty on hadronic effects or if it requires a New Physics explanation
Since the form-factors for broad resonances remain poorly known, a more model-independent prescription was provided in ref. [12], which is used in this analysis
Summary
The final state of the decay B0 → K+π−μ+μ− is fully described by five kinematic variables: three decay angles (θ , θK, φ), m(K+π−), and q2. An additional minus sign is added to the dihedral angle when performing the CP conjugation, in order to keep the measured angular observables the same between B0 and B0 in the absence of direct CP violation. The measured angular observables are averaged over the range 1330 < m(K+π−) < 1530 MeV/c2 and 1.1 < q2 < 6.0 GeV2/c4 This q2 range is part of the large-recoil regime where the recoiling K∗0 has a relatively large energy, EK∗0, as measured in the rest frame of the parent B meson. The first moment, Γ1(q2), corresponds to the total decay rate
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