B →Vℓ+ℓ− in the Standard Model from light-cone sum rules

Abstract

We present B q → ρ, B q → ω, B q → K * , B s → K * and B s → φ form factors from light-cone sum rules (LCSR) at O(α s ) for twist-2 and 3 and O(α 0 s ) for twist-4 with updated hadronic input parameters. Three asymptotic light-cone distribution amplitudes of twist-4 (and 5) are determined, necessary for the form factors to obey the equations of motion. It is argued that the latter constrain the uncertainty of tensor-to-vector form factor ratios thereby improving the prediction of zeros of helicity amplitudes of major importance for B → K * angular observables. We provide easy-to-use fits to the LCSR results, including the full error correlation matrix, in all modes at low q 2 as well as combined fits to LCSR and lattice results covering the entire kinematic range for B q → K * , B s → K * and B s → φ. The error correlation matrix avoids the problem of overestimating the uncertainty in phenomenological applications. Using the new form factors and recent computations of non-factorisable contributions we provide Standard Model predictions for B → K * γ as well as B → K * + − and B s → φµ + µ − at low dilepton invariant mass. Employing our B → (ρ, ω) form factor results we extract the CKM element |V ub | from the semileptonic decays B → (ρ, ω) ν and find good agreement with other exclusive determinations.

Large hadronic power corrections or new physics in the rare decay B → K ∗ μ + μ −?

“…If the experimental result is reconfirmed with future measurements, flavour violating NP contributions would be the most probable explanation. Interestingly, this 2.6σ deviation can also be explained with a similar NP contribution to C 9 like the anomalies in the angular observables [15,18,[23][24][25][26][27][28]. Thus, a confirmation of the deviation in R K would also indirectly confirm the NP interpretation of the anomalies in the angular observables.…”

“…There are also slight theoretical differences, where we have employed the updated LCSR form factor calculations of ref. [27]. In addition, for the experimental results on BR(B → K * µ + µ − ) we have used the updated LHCb measurement [44] and we do not include BR(B → K * γ) which has been considered by ref.…”

“…[15], we show that the deviation can be reduced by doubling the error in the form factor calculation of ref. [27]. So one cannot rule out the option that the present anomalies are partially a result of underestimated uncertainties in the form factor determination.…”

“…Recently new LCSR results on the B → K * form factors, which also include the correlations among the form factor uncertainties have been presented [27]. Even if the B → K * form factors were precisely known, there would still be another source of hadronic uncertainty.…”

CP violation in multibody B decays from QCD factorization

“…where f ρ = 0.209 GeV and A 0 (m 2 π ) A 0 (0) = 0.36 ± 0.04 [26,27]. A similar procedure can be applied to the I = 0 channel, assuming dominance of a scalar resonance, B → S 0 → ππ.…”