In pursuit of new physics with Bd 0→J/ΨK0 and Bs 0→J/Ψφ decays at the high-precision frontier

Abstract The decays B d 0 → J / ψ K S 0 and B s 0 → J / ψ ϕ play a key role for the determination of the B q 0 – B ̄ q 0 (q = d, s) mixing phases ϕ d and ϕ s , respectively. The theoretical precision of the extraction of these quantities is limited by doubly Cabibbo-suppressed penguin topologies, which can be included through control channels by means of the SU(3) flavour symmetry of strong interactions. Using the currently available data and a new simultaneous analysis, we discuss the state-of-the-art picture of these effects and include them in the extracted ϕ q values. We have a critical look at the standard model predictions of these phases and explore the room left for new physics. Considering future scenarios for the high-precision era of flavour physics, we illustrate that we may obtain signals for physics beyond the standard model with a significance well above five standard deviations. We also determine effective colour-suppression factors of B d 0 → J / ψ K 0 , B s 0 → J / ψ K S 0 and B d 0 → J / ψ π 0 decays, which serve as benchmarks for QCD calculations of the underlying decay dynamics, and present a new method using information from semileptonic B d 0 → π − ℓ + ν ℓ and B s 0 → K − ℓ + ν ℓ decays.