Bs Lifetime in Bs&rarr Ds(φπ)X

This web page summarizes the results for the blind measurement of the Bs lifetime performed using 1.3fb-1 of data reconstructed as Bs → Ds- (φ π-+ . In addition to the more than 1100 fully reconstructed Bs → Ds- (φ π-+ candidates, the sample reconstructed as Bs → Ds- π+ includes a similar number of partially reconstructed Bs candidates, e.g. Bs → Ds- ρ++ π0) where the π0 is not reconstructed. Since these candidates come from actual Bs mesons, they can contribute to the lifetime measurement and double the statistics available for analysis. The increased statistics come with an uncertainty due to missing tracks or misassigned masses, but it can be properly accounted for and folded into the likelihood formulation.


The results have been approved as of February 7, 2008.

On October 23, 2008 the analysis was reblessed with the following changes:

A more detailed summary of the results can be found in this public note.

We measure:

cτ(Bs) = 455.0 ± 12.2 (stat.) ± 8.2 (syst.) μm


Below are the eps and gif versions of all figures meant for download.

The numbered figures can be found in the public note with the same numbers and expanded descriptions.

Signal Sample

Control Samples


Below are the eps and gif versions of additional support figures.

Auxilliary background fits

K - factor distributions

Effect of the displaced-track trigger on the expected mixture of Bs,L and Bs,H in a flavor-specific decay as a function of ΔΓ/Γ

Comparison with flavor specific Bs measurements that are already in the PDG 2007 average. NOTE: The PDG average quoted is for the flavor specific modes only.