New physics in B _q ⁰– B¯q0 mixing: present challenges, prospects, and implications for Bq0⃗μ+μ−

Abstract

The phenomenon of Bq 0B q 0 mixing (q=d,s) provides a sensitive probe for physics beyond the Standard Model. We explore the corresponding space for New Physics left through the current data, having a careful look at analyses of the Unitarity Triangle that are needed for the Standard Model predictions of the Bq mixing parameters. In particular, we explore the impact of tensions between inclusive and exclusive determinations of the CKM matrix elements |Vub| and |Vcb|. Moreover, we focus on the angle γ of the Unitarity Triangle, comparing measurements from B→DK and B→ππ, ρπ, ρρ decays, where the latter are typically interpreted in terms of the angle α. We discuss various scenarios and present the corresponding state-of-the-art constraints on the New Physics parameters of Bq 0B q 0 mixing. We point out that these results have an interesting application in the analysis of rare Bq 0→μ+μ- decays, allowing us to minimise the impact of CKM parameters in the search for New Physics. In view of the high-precision era, we make future projections. Interestingly, we find that for the extraction of the New Physics parameters in the Bd system the determination of the apex of the Unitarity Triangle results in a key limiting factor. By contrast, the corresponding impact is negligible for the Bs system, making it a promising candidate to reveal sources of New Physics.

Studies of New Physics in $B^0_q-\bar{B}^0_q$ Mixing and Implications for Leptonic Decays

“…The value from the latter case is in good agreement with the one coming from 𝐵 → 𝐷𝐾 modes. Therefore, for our analysis, we average these two results [1]:…”

“…However, in order to get the 𝑅 𝑡 , we have to assume SM expressions for the mixing parameters Δ𝑚 𝑑 and Δ𝑚 𝑠 . The numerical predictions are given in [1].…”

“…The advantage of the ratio is that uncertainties cancel, making it cleaner than using individual results. Making a fit to the 𝑅 𝑏 and 𝑅 𝑡 sides, we obtain [1]:…”

“…This is a model independent parametrization. Utilising these relations, we explore two different NP scenarios; the first one is the most general case and the second one assumes Flavour Universal NP (FUNP) [1]. Let us firstly discuss the general case, namely Scenario I.…”

“…In this presentation, we follow Ref. [1] and explore the space allowed for NP by current measurements and the state-of-the-art parameters. In addition, we point out interesting connections to the studies of leptonic rare 𝐵 decays.…”