Abstract
We assume that the quark-flavor coefficients matrix of the semileptonic operators addressing the neutral-current B-meson anomalies has rank-one, i.e. it can be described by a single vector in quark-flavor space. By correlating the observed anomalies to other flavor and high-pT observables, we constrain its possible directions and we show that a large region of the parameter space of this framework will be explored by flavor data from the NA62, KOTO, LHCb and Belle II experiments.
Highlights
It has recently been pointed out that allowing for NP in both muons and electrons provides a slight improvement in the fits [26,27,28]
By correlating the observed anomalies to other flavor and high-pT observables, we constrain its possible directions and we show that a large region of the parameter space of this framework will be explored by flavor data from the NA62, KOTO, LHCb and Belle II experiments
Assuming that the relevant NP degrees of freedom lie above the electroweak scale, the natural framework for model-independent studies of the anomalies is that of the Standard Model Effective Field Theory (SMEFT)
Summary
We study the correlations that follow directly from the rank-one condition, for all models in which NP couples only to left-handed fermions. Since a non-zero phase necessarily implies a lower Λbs scale in order to fit the anomalies, to be conservative we fix αbs = 0. In this case the best-fit point for the NP scale is (Λbs)best-fit = 38.5 TeV (αbs ≡ 0). We constrain n (or, more precisely, θ and φ for given αbs) using the other observables correlated with RK by the relation CLij = CLnin∗j. (LHCb [46]) and KL → μ+μ− (E871 [50, 51]) The latter observable does not yield any bound for αbd − αbs = π/2, i.e. for Re CLds = 0. While these are known to be too constrained to give significant contributions to RK(∗) (see e.g. [11]), they may produce important effects in other observables, so that some of the bounds discussed here may be relaxed, if some degree of fine-tuning is allowed
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