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

Measurement of mixing-induced CP violation in B¯s0 decays is of prime importance in probing new physics. So far only the channel B¯s0→J/ψϕ 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/ψf0(980), where f0(980)→π+π−. A time-dependent fit of the data with the B¯s0 lifetime and the difference in widths of the heavy and light eigenstates constrained to the values obtained from B¯s0→J/ψϕ yields a value of the CP violating phase of −0.44±0.44±0.02 rad, consistent with the Standard Model expectation.