Charming New $B$-Physics

TL;DR

This paper provides a comprehensive analysis of BSM effects in $b o c ar{c} s$ transitions, constraining new physics operators and exploring their impact on lifetime observables and CP violation in B-meson decays.

Contribution

It offers the first complete results for BSM effects on lifetime observables and extends previous analyses to include CP-violating effects, with detailed constraints on 20 operators.

Findings

Stringent constraints on 16 of 20 BSM operators, including right-handed strange quark operators.

NP scales of order 10 TeV for most operators, dominated by B-decay data.

Viable regions for new physics in SM operators affecting CP violation and decay rates.

Abstract

We give a comprehensive account of the flavour physics of Beyond-Standard-Model (BSM) effects in $b \to c \bar{c} s$ 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 $\Delta \Gamma_s$ and $\tau(B_s)/\tau(B_d)$, as well as for the semileptonic CP-asymmetry $a_{sl}^s$. From a global analysis, we obtain stringent constraints on 16 of the 20 BSM operators, including the 10 operators $Q^{c\prime }_{1 \dots 10}$ 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 arXiv:1701.09183. 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 $B_d \to J/\psi K_S$. 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 operator determined from the data. For new physics in the SM suppressed coefficient $C^c_1$ we find 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 $B_d \to J/\psi K_S$ are implied by experimental data.