This web page summarizes the results for the blind measurement of the B_s lifetime performed using 1.3fb^-1 of data reconstructed as B_s → D_s^- (φ π^-)π⁺ . In addition to the more than 1100 fully reconstructed B_s → D_s^- (φ π^-)π⁺ candidates, the sample reconstructed as B_s → D_s^- π⁺ includes a similar number of partially reconstructed B_s candidates, e.g. B_s → D_s^- ρ⁺(π⁺ π⁰) where the π⁰ is not reconstructed. Since these candidates come from actual B_s 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:

• The systematic uncertainty for the SVX alignment has been changed to 1.0 μm from 2.4 μm to avoid the double counting of systematic effects.
• We now include a 4.1 μm systematic uncertainty for SVT modeling.
• The total systematic uncertainty for τ(B_s) has been changed from 7.4 μm to 8.2 μm.
• The calculations of the effect of the displaced-track trigger on the expected mixture of B_s,L and B_s,H in a flavor-specific decay as a function of ΔΓ/Γ has been corrected. The figure has been updated.

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

We measure:

cτ(B_s) = 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

• Figure 4: B_s→D_s^-(φπ^-)π⁺ mass (.eps) (.gif)
• Figure 5a: B_s→D_s^-(φπ^-)π⁺ lifetime fit (m(B)∈[5.35,5.45]GeV - fully reconstructed region) (.eps) (.gif)
• Figure 5b: B_s→D_s^-(φπ^-)π⁺ lifetime fit (m(B)∈[5.00,5.35]GeV - partially reconstructed region) (.eps) (.gif)
• Figure 5c: B_s→D_s^-(φπ^-)π⁺ lifetime fit (m(B)∈[5.00,5.45]GeV - combined region) (.eps) (.gif)

Control Samples

• B⁰→D^-(K⁺π^-π^-)π⁺ mass (.eps) (.gif)
• B⁰→D^-(K⁺π^-π^-)π⁺ lifetime fit (m(B)∈[5.15,5.35]GeV - fully reconstructed region) (.eps) (.gif)
• B⁰→D^-(K⁺π^-π^-)π⁺ lifetime fit (m(B)∈[5.00,5.15]GeV - partially reconstructed region) (.eps) (.gif)
• B⁰→D^-(K⁺π^-π^-)π⁺ lifetime fit (m(B)∈[5.00,5.35]GeV - combined region) (.eps) (.gif)


• B⁰→D*^-[D⁰(K⁺π^-)π^-]π⁺ mass (.eps) (.gif)
• B⁰→D*^-[D⁰(K⁺π^-)π^-]π⁺ lifetime fit (m(B)∈[5.15,5.35]GeV - fully reconstructed region) (.eps) (.gif)
• B⁰→D*^-[D⁰(K⁺π^-)π^-]π⁺ lifetime fit (m(B)∈[5.00,5.15]GeV - partially reconstructed region) (.eps) (.gif)
• B⁰→D*^-[D⁰(K⁺π^-)π^-]π⁺ lifetime fit (m(B)∈[5.00,5.35]GeV - combined region) (.eps) (.gif)


• B⁺→D⁰(K⁺π^-)π⁺ mass (.eps) (.gif)
• B⁺→D⁰(K⁺π^-)π⁺ lifetime fit (m(B)∈[5.15,5.35]GeV - fully reconstructed region) (.eps) (.gif)
• B⁺→D⁰(K⁺π^-)π⁺ lifetime fit (m(B)∈[5.00,5.15]GeV - partially reconstructed region) (.eps) (.gif)
• B⁺→D⁰(K⁺π^-)π⁺ lifetime fit (m(B)∈[5.00,5.35]GeV - combined region) (.eps) (.gif)

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

Auxilliary background fits

• Wrong-Sign mass fit - D^-(K⁺π^-π^-)π^- (.eps) (.gif)
• Figure 3: Wrong-Sign mass fit - D_s^-(φπ^-)π^- (.eps) (.gif)


• D sideband mass fit - B⁰→D^-(K⁺π^-π^-)π⁺ (.eps) (.gif)
• D sideband mass fit - B⁺→D⁰(K⁺π^-)π⁺ (.eps) (.gif)
• Figure 2: D sideband mass fit - B_s→D_s^-(φπ^-)π⁺ (.eps) (.gif)

K - factor distributions

• B⁰→D^-(K⁺π^-π^-)X partially reconstructed modes (.eps) (.gif)
• B⁰→D*^-[D⁰(K⁺π^-)π^-]X partially reconstructed modes (.eps) (.gif)
• B⁺→D⁰(K⁺π^-)X partially reconstructed modes (.eps) (.gif)
• Figure 1: B_s→D_s^-(φπ^-)X partially reconstructed modes (.eps) (.gif)

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

• Figure 6: B_s→D_s^-(φπ^-)π⁺ mixture (.eps) (.gif)

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

• Comparison with published results (.eps) (.gif)