Emerging patterns of New Physics with and without Lepton Flavour Universal contributions

Abstract

We perform a model-independent global fit to b → s + − observables to confirm existing New Physics (NP) patterns (or scenarios) and to identify new ones emerging from the inclusion of the updated LHCb and Belle measurements of RK and RK * , respectively. Our analysis, updating Refs. [1,2] and including these new data, suggests the presence of right-handed couplings encoded in the Wilson coefficients C 9 µ and C 10 µ . It also strengthens our earlier observation that a lepton flavour universality violating (LFUV) left-handed lepton coupling (C V 9µ = −C V 10µ ), often preferred from the model building point of view, accommodates the data better if lepton-flavour universal (LFU) NP is allowed, in particular in C U 9 . Furthermore, this scenario with LFU NP provides a simple and model-independent connection to the b → cτ ν anomalies, showing a preference of ≈ 7 σ with respect to the SM. It may also explain why fits to the whole set of b → s + − data or to the subset of LFUV data exhibit stronger preferences for different NP scenarios. Finally, motivated by Z models with vector-like quarks, we propose four new scenarios with LFU and LFUV NP contributions that give a very good fit to data. PACS numbers: 13.25.Hw, 11.30.Hv R [15,19] K * = 1.18 +0.52 −0.32 ± 0.10 . Our treatment for the Belle observables within the global fit follows the same strategy as described in Ref. [1] for arXiv:1903.09578v4 [hep-ph]

With or without U(2)? Probing non-standard flavor and helicity structures in semileptonic B decays

“…As pointed out in [55], a possible large enhancement of the b → sττ amplitude can indirectly be tested via the one-loop-induced lepton-universal contributions to b → s ¯ ( = e, µ, τ ) in the O 9 direction (see below). This contribution is well compatible and even favored by current data [30,56].…”

∆Ms theory precision confronts flavour anomalies

“…On the other hand, the recent update of R K at Moriond 2019 [42] favours a non-zero RH quark current contribution, as widely discussed in the literature since then (see e.g. [54][55][56][57][58][59][60]). There is however a problem with this solution, which is that in our Z model, at the leading order in the NP contribution, the behaviour can be written as has shrunk by only a small amount, and so our benchmark point is only marginally more favoured.…”

“…Intriguingly, one obtains a very good description of the b → s data by allowing new physics only in a single combination of Wilson coefficients (for recent fits see e.g. [54][55][56][57][58][59][60]). The best-fit scenario δC µ 9 = −δC µ 10 ≈ −0.53 ± 0.08 of [54] corresponds to an effective operator with left-handed (LH) quark and muon currents and we consider its interplay with ∆M s in Section 3.4.…”

Light-cone sum rules for B → K π form factors and applications to rare decays

“…This 20% increase in the theory predictions with respect to the narrow-width limit is very relevant phenomenologically in view of the systematically low experimental determinations of branching ratios in b → sµµ modes reported by the LHCb collaboration (see for instance Refs. [1,2,63,64] and references therein). The correction to the NWL discussed here would tend to increase the discrepancy between the SM predictions and the LHCb measurements.…”