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Article

Measurement of the CP-violating phase ϕs from Bs0→ J/ψπ+ π− decays in 13 TeV pp collisions

Decays of B 0 s and B 0 s mesons into J /ψ π + π − final states are studied in a data sample corresponding to 1.9 fb − 1 of integrated luminosity collected with the LHCb detector in 13 TeV pp collisions. A time-dependent amplitude analysis is used to determine the final-state resonance contributions, the CP -violating phase φ s = − 0 . 057 ± 0 . 060 ± 0 . 011 rad, the decay-width difference between the heavier mass B 0 s eigenstate and the B 0 meson of − 0 . 050 ± 0 . 004 ± 0 . 004 ps − 1 , and the CP -violating parameter 0 . 08 |λ| = 1 . 01 + − 0 . 06 ± 0 . 03, where the first uncertainty is statistical and the second systematic. These results are combined with previous LHCb measurements in the same decay channel using 7 TeV and 8 TeV pp collisions obtaining φ s = 0 . 002 ± 0 . 044 ± 0 . 012 rad, and |λ| = 0 . 949 ± 0 . 036 ± 0 . 019