Abstract
We conduct a systematic study of the impact of new physics in quark-level $b \to c \bar{c} s$ transitions on $B$-physics, in particular rare $B$-decays and $B$-meson lifetime observables. We find viable scenarios where a sizable effect in rare semileptonic $B$-decays can be generated, compatible with experimental indications and with a possible dependence on the dilepton invariant mass, while being consistent with constraints from radiative $B$-decay and the measured $B_s$ width difference. We show how, if the effect is generated at the weak scale or beyond, strong renormalisation-group effects can enhance the impact on semileptonic decays while leaving radiative $B$-decay largely unaffected. A good complementarity of the different $B$-physics observables implies that precise measurements of lifetime observables at LHCb may be able to confirm, refine, or rule out this scenario.
Highlights
Rare B decays are excellent probes of new physics at the electroweak scale and beyond, due to their strong suppression in the Standard Model (SM)
Experimental data on rare branching ratios [1,2] and angular distributions for B → KðÃÞμþμ− decay [2,3] may hint at a beyond-SM (BSM) contact interaction of the form ðsLγμbLÞðμγμμÞ, which would destructively interfere with the corresponding SM coupling C9 [4,5,6], the significance of the effect is somewhat uncertain because of form-factor uncertainties as well as uncertain long-distance virtual charm contributions [7]
Noting that in the SM, about half of C9 comes from virtual-charm contributions, in this article we ask whether new physics affecting the quark-level b → ccs transitions could cause the anomalies, affecting rare B
Summary
Rare B decays are excellent probes of new physics at the electroweak scale and beyond, due to their strong suppression in the Standard Model (SM). At the same time, such a scenario offers the exciting prospect of confirming the rare B-decay anomalies through correlated effects in hadronic B decays into charm, with “mixing” observables such as the Bs-meson width difference standing out as precisely measured [9] and under reasonable theoretical control. This is in contrast with the Z0 and leptoquark models usually considered, where correlated effects are typically restricted to other rare processes and are highly model dependent. Very strong renormalization-group effects can generate large shifts in the (low-energy) effective C9 coupling from small b → ccs couplings at a high scale without conflicting with the measured B → Xsγ decay rate [13]
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