New strategies to obtain insights into CP violation through Bs→Ds±K∓,Ds∗±K∓,… and Bd→D±π∓,D∗±π∓,… decays Original Research Article

Decays of the kind Bs→Ds±K∓,Ds∗±K∓,… and Bd→D±π∓,D∗±π∓,… allow us to probe φs+γ and φd+γ, respectively, involving the angle γ of the unitarity triangle and the B0q–B 0q mixing phases φq (q∈{d,s}). Analysing these modes in a phase-convention-independent way, we find that their mixing-induced observables are affected by a subtle (−1)L factor, where L denotes the angular momentum of the Bq decay products, and derive bounds on φq+γ. Moreover, we emphasize that “untagged” rates are an important ingredient for efficient determinations of weak phases, not only in the presence of a sizeable width difference ΔΓq; should ΔΓs be sizeable, the combination of “untagged” with “tagged” Bs→Ds±K∓,Ds∗±K∓,… observables provides an elegant and unambiguous extraction of tan(φs+γ), whereas the “conventional” determination of φs+γ is affected by an eightfold discrete ambiguity. Finally, we propose a combined analysis of Bs→Ds±K∓,Ds∗±K∓,… and Bd→D±π∓,D∗±π∓,… modes, which has important advantages, offering various interesting new strategies to extract γ in an essentially unambiguous manner.