Implications of the new LHCb angular analysis of B→K*μ+μ− : Hadronic effects or new physics?

Abstract

The new angular analysis of the decay B → K Ã l þ l − recently presented by the LHCb Collaboration still indicates some tensions with the Standard Model predictions. There are several ongoing analyses to solve the problem of separating hadronic and new physics effects in this decay, but the significance of the observed tensions in the angular observables in B → K Ã μ þ μ − is still dependent on a theory guesstimate of the hadronic contributions to these decays. Using the new data from LHCb, we offer two tests which make a statistical comparison to determine whether the most favored explanation of the anomalies is new physics or underestimated hadronic effects. We then analyze the usefulness of these tests in two future scenarios. Finally, we update our global fits to all available b → s data and discuss the impact of the new LHCb measurements.

Low scale U(1)X gauge symmetry as an origin of dark matter, neutrino mass and flavour anomalies

“…For these values of [n 2 , n 1 ] and for g X = 0.001, within the allowed ranges of q 2 and M X the numerical values of the WCs ∆C µ 9 and ∆C e 9 will lie in between [−0.827, −1.83] and [0.413, 0.91], respectively. These values of the WCs are consistent with the result (within 2σ CI) obtained from a global fit to all the available data in b → s decays considering NP effects in both the muon and electron final states [18].…”

“…However, there are theoretically clean observables like R(K ( * ) ) = B(B→K ( * ) µ + µ − ) B(B→K ( * ) e + e − ) the measured values of which [14,15] are not in good agreement with the corresponding SM expectations. There are new physics explanations of these observations, for a recent update on the model-independent new physics explanation of these data see [16][17][18] and the references therein. Similar to the observables R(K ( * ) ), we define R(D ( * ) ) = B(B→D ( * ) τ ντ ) B(B→D ( * ) ν ) (with = µ, e) which is associated with the b → c decays.…”

The impact of flavour data on global fits of the MFV SMEFT

“…We do not fit to observables that test lepton flavour universality, or lepton flavour violation, since under our flavour assumptions these will not be altered from their SM predictions. We also exclude angular observables in the decay B → K * µµ from the fit, due to the presence of as-yet unknown power corrections in the theory predictions which could mimic some effects of BSM physics [45][46][47][48][49][50][51][52][53][54]. If a real estimate of these power corrections were established and found not to be too large, including these observables in the fit would have the effect of shrinking the errors on the Wilson coefficients slightly, and moving the central value of C bs 9 (µ b ) further from zero.…”

B anomalies under the lens of electroweak precision

“…However, long-distant effects present in the amplitude of these processes [39][40][41][42][43] -involving hadronic contributions that are theoretically difficult to handle [44][45][46][47] -make such a conclusion debatable, see, e.g. [48,49]. From this point of view, the LUV information extracted from ratios of branching ratios and from observables like the ones considered in [50][51][52][53] remain the most promising avenue in the future for a more precise assessment of the overall tension seen in b → s measurements [54].…”