  Measurement of mixing-induced CP violation in Bs decays is of prime
importance in probing new physics. So far only the channel Bs->J/\psi \phi\ has
been used. Here we report on a measurement using an LHCb data sample of 0.41/fb
in the CP odd eigenstate J\psi f0(980), where f0(980)->\pi+ \pi-. A time
dependent fit of the data with the Bs lifetime and the difference in widths of
the heavy and light eigenstates constrained to the values obtained from Bs->
J/\psi\phi\ yields a value of the CP violating phase of -0.44 +/- 0.44 +/- 0.02
rad, consistent with the Standard Model expectation.
