**Primary Authors: Michael Feindt, Matthias Huschle, Michal Kreps,
Thomas Kuhr**

In the standard model, the mass and flavor eigenstates
of the B_{s} meson differ. This gives rise to
particle-antiparticle oscillations, which proceed in
the SM through weak interaction processes, and whose
phenomenology depends on the Cabibbo-Kobayashi-Maskawa (CKM)
quark mixing matrix. The time evolution of B_{s} mesons
is governed by a Schrödinger equation which contains two 2x2 matrices,
called mass and decay matrix. The off-diagonal
elements are related to observable quantities, namely the mass difference
Δm_{s}, the phase φ_{s} between the off-diagonal elements
of mass and decay matrices, and the decay width difference
ΔΓ_{s}. ΔΓ_{s} depends on the
product of the off-diagonal element of the decay matrix and the cosine of the phase
φ_{s}. A special feature of the B_{s} system is the large
value of ΔΓ_{s}, which yields a significant difference in the lifetimes of the
two mass eigenstates of the B_{s}. Within the standard model
φ_{s} is predicted to be very small, which in consequence means that
CP- and mass-eigenstates coincide.

A large sample of B_{s}→J/ψf_{0}(980) decays with
f_{0}(980)→π^{+}π^{-} available at the CDF
experiment allows us to directly measure for the first time the lifetime of the heavy
B_{s} eigenstate. The
analysis is based on 3.8 fb^{-1} of data collected by a dimuon
trigger. The result contributes to the determination of the decay width
difference between the two B_{s} mass eigenstates.

Further information can be found in the arXiv:1106.3682.

We measure

τ(B_{s}→J/ψf_{0}(980))=
1.70_{-0.11}^{+0.12}(stat.)±0.03(syst.) ps

which is in good agreement with theoretical expectations as well as with other determinations of the B_{s,H}
lifetime.

- Figure 1: Projection of the fit on invariant mass space: (pdf) (eps) (png)
- Figure 2: Projection of the fit on proper decay time space: (pdf) (eps) (png)
- Figure 3: Projection of the fit on proper decay time uncertainty space: (pdf) (eps) (png)
- Figure 4: Comparison of measured lifetime to predictions and other determinations: (pdf) (eps) (png)