Abstract
Long distance effects are studied in the rare exclusive semileptonic B(d,s) → Vℓ+ℓ− decays, where V denotes a K* or ϕ meson. The form factors, which describe the meson transition amplitudes in the effective Hamiltonian approach, are calculated by means of Ward identities, experimental constraints and extrapolated within a general vector meson dominance framework. These form factors are then compared to the ones obtained in Lattice QCD simulations, with Light Cone Sum Rules and a Dyson-Schwinger equation approach. Additionally, the Bd → K*ℓ+ℓ− and Bs → ϕℓ+ℓ− branching ratios are computed and the differential branching fractions are given as a function of the squared-momentum transfer.
Highlights
Rare B meson decays have been a subject of great interest for the past two decades
The form factors, which describe the meson transition amplitudes in the effective Hamiltonian approach, are calculated by means of Ward identities, experimental constraints and extrapolated within a general vector meson dominance framework. These form factors are compared to the ones obtained in Lattice QCD simulations, with Light Cone Sum Rules and a Dyson-Schwinger equation approach
Exclusive decays are more challenging due to the uncertainties in the calculation of hadronic transition form factors which, so far, are model-dependent quantities when computed for the entire range of squared momentum transfer q2
Summary
Rare B meson decays have been a subject of great interest for the past two decades. These decays provide a stringent tests of the Standard Model (SM), and serve as a tool to extract physics beyond the SM in the flavor sector. Different frameworks have been used to compute transition form factors, namely within the constituent quark model (CQM), light cone sum rules (LCSR), QCD sum rules (QCDSR), Dyson-Schwinger equation (DSE) approaches and lattice QCD (LQCD) amongst others These form factors are the ingredients of physical observables, such as branching ratios and different asymmetries related to final particle states, especially in B → K(K∗) + − [4, 5, 6], B → γ + − [7] decays. We study the transition form factors, Bd → K∗ and Bs → φ, using Ward identities to compute their values at q2 = 0 and extrapolate them in a general vector meson dominance model to larger q2 values. Eqs. (1) and (2) as well as with the predictions of the LCSR, Lattice QCD and DSE approaches
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