Primary Author: Michal Kreps
Since the Bs mixing observation in 2006 particle physics community is excited by searches for CP violation in Bs→J/ψφ decays. The first results, which used flavor tagging to separate Bs and anti-Bs, showed about 1.5σ deviations from the standard model. In the initial measurements of both Tevatron experiments as well as in the subsequent CDF update a possible contribution from the so-called S-wave contribution was neglected. The S-wave component itself can be non-resonant Bs→J/ψ K+K- decay or decay Bs→J/ψf0(980) with f0(980)→K+K-. It was argued that the mild deviation from the SM could have been due to ignoring the S-wave contribution rather than real genuine effect. A summary of the discussion can be find in work of Stone (arXiv:1009.4939). It is also suggested that sufficient signal for the decay Bs→J/ψf0(980) with f0(980)→π+π- can be used to measure CP violating phase βsJ/ψφ without need of angular analysis. All this generated interest in the decay Bs→J/ψf0(980).
Several estimations for Rf0/φ, the ratio of branching fractions between Bs→J/ψf0(980) and Bs→J/ψφ, exist based on theoretical calculations as well as on comparison to Ds decays. They vary in wide range of 0.1 to 0.5. Here we present observation of the Bs→J/ψf0(980) decay with f0(980)→π+π- in CDF data and a measurement of Rf0/φ. The analysis is based on 3.8 fb-1 of data collected by dimuon trigger.
Further information can be found in the arXiv:1106.3682.