First direct measurement of the Bs,H lifetime in Bs→J/ψf0(980) decays at CDF

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


In the standard model, the mass and flavor eigenstates of the Bs 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 Bs 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 Δms, the phase φs between the off-diagonal elements of mass and decay matrices, and the decay width difference ΔΓs. ΔΓs depends on the product of the off-diagonal element of the decay matrix and the cosine of the phase φs. A special feature of the Bs system is the large value of ΔΓs, which yields a significant difference in the lifetimes of the two mass eigenstates of the Bs. Within the standard model φs is predicted to be very small, which in consequence means that CP- and mass-eigenstates coincide.

A large sample of Bs→J/ψf0(980) decays with f0(980)→π+π- available at the CDF experiment allows us to directly measure for the first time the lifetime of the heavy Bs 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 Bs mass eigenstates.

Further information can be found in the arXiv:1106.3682.


We measure
τ(Bs→J/ψf0(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 Bs,H lifetime.

List of Figures