Measurement of time-dependent $CP$-violating asymmetries in $B^0\to\pi^+\pi^-$ and $B_s^0\to K^+K^-$ decays at LHCb

Using a data sample of p p collisions corresponding to an integrated luminosity of 3 fb − 1 , collected with the LHCb detector at a centre-of-mass energies of 7 and 8 TeV, the CP -violating asymmetries in the decay and in the interference between mixing and decay in the B 0 → π + π − and B 0 s → K + K − modes are measured. The results are C π + π − = − 0 . 24 ± 0 . 07 ± 0 . 01, S π + π − = − 0 . 68 ± 0 . 06 ± 0 . 01, C K + K − = 0 . 24 ± 0 . 06 ± 0 . 02, S K + K − = 0 . 22 ± 0 . 06 ± 0 . 02, and A ∆Γ K + K − = − 0 . 75 ± 0 . 07 ± 0 . 11, where the first uncertainties are statistical and the second systematic.