Charming new B-physics

Abstract

Abstract We give a comprehensive account of the flavour physics of Beyond-Standard-Model (BSM) effects in b → c$$ \overline{c} $$ c ¯ cs transitions, considering the full set of 20 four-quark operators. We discuss the leading-order structure of their RG mixing with each other as well as the QCD-penguin, dipole, and FCNC semileptonic operators they necessarily mix with, providing compact expressions. We also provide the first complete results for BSM effects in the lifetime observables ∆Γs and τ (Bs)/τ(Bd), as well as for the semileptonic CP-asymmetry $$ {a}_{sl}^s $$ a sl s . From a global analysis, we obtain stringent constraints on 16 of the 20 BSM operators, including the 10 operators $$ {Q}_{1\dots 10}^{c\prime } $$ Q 1 … 10 c ′ involving a right-handed strange quark. Focussing on CP-conserving new physics, the constraints correspond to NP scales of order 10 TeV in most cases, always dominated by exclusive and/or radiative B-decays via RGE mixing. For the remaining four operators, including the two Standard-Model (SM) ones, larger effects are experimentally allowed, as previously noted in [1]. We extend that paper’s scope to the CP-violating case, paying attention to the impact on the decay rate and time-dependent CP-violation in Bd → J/ψKS. Contrary to common lore, we show that quantifiable constraints arise for new physics in either of the two SM operators, with the uncertain non-perturbative matrix element of the colour-suppressed (or equivalently, colour-octet) operator determined from the data. For new physics in the coefficient $$ {C}_1^c $$ C 1 c , suppressed in the SM, we find (in addition to CP-conserving new physics) two perfectly viable, narrow bands of complex Wilson coefficients. Somewhat curiously, one of them contains a region where the fitted matrix element for the colour-suppressed operator is in agreement with naive factorization, contrarily to a widely held belief that large non- factorizable contributions to Bd → J/ψKS are implied by experimental data.