Measurement of the CKM angle γ and Bs0‐B¯s0 mixing frequency with Bs0→Ds∓h±π±π∓ decays

Abstract

The CKM angle γ is measured for the first time from mixing-induced CP violation between B0 s → D∓ s K±π ±π ∓ and B 0 s → D± s K∓π ∓π ± decays reconstructed in proton-proton collision data corresponding to an integrated luminosity of 9 fb−1 recorded with the LHCb detector. A time-dependent amplitude analysis is performed to extract the CP-violating weak phase γ − 2βs and, subsequently, γ by taking the B0 s -B 0 s mixing phase βs as an external input. The measurement yields γ = (44±12)◦ modulo 180◦ , where statistical and systematic uncertainties are combined. An alternative model-independent measurement, integrating over the five-dimensional phase space of the decay, yields γ = (44 + 20 − 13) ◦ modulo 180◦ . Moreover, the B0 s -B 0 s oscillation frequency is measured from the flavour-specific control channel B0 s → D− s π +π +π − to be ∆ms = (17.757 ± 0.007(stat) ± 0.008(syst)) ps−1 , consistent with and more precise than the current world-average value.