Measurement of the CP violating phase ϕs in B¯s0→J/ψf0(980)

Abstract Measurement of mixing-induced CP violation in B ¯ s 0 decays is of prime importance in probing new physics. So far only the channel B ¯ s 0 → J / ψ ϕ has been used. Here we report on a measurement using an LHCb data sample of 0.41 fb −1 , in the CP odd eigenstate J / ψ f 0 ( 980 ) , where f 0 ( 980 ) → π + π − . A time-dependent fit of the data with the B ¯ s 0 lifetime and the difference in widths of the heavy and light eigenstates constrained to the values obtained from B ¯ s 0 → J / ψ ϕ yields a value of the CP violating phase of − 0.44 ± 0.44 ± 0.02 rad , consistent with the Standard Model expectation.