Measurement of the B hadron Lifetimes in the modes B+ → J/&psi K+,
B0 → J/&psi K*0, B0 → J/&psi K0s, and /\b → J/&psi /\, and measurement of the B+/B0, and /\b/B0 lifetime ratios
Primary authors: Joe Boudreau, Juan Pablo Fernandez, Sneha Malde
This web page summarizes the results for the measurement
of the above B hadron's lifetimes performed using the above fully reconstructed decay channels that include a J/&psi . The measurement uses 4.3 fb-1 of data.
The results were approved on December 17, 2009.
This result supersedes the previous measurement performed with 1fb-1.
We measure:
- &tau(B+) = 1.639 ± 0.009(stat.) ± 0.009 (syst.) ps
- &tau(B0) = 1.507 ± 0.010(stat.) ± 0.008 (syst.) ps
- &tau(/\b) = 1.537 ± 0.045 (stat.) ± 0.014 (syst.) ps
- &tau(B+)/&tau(B0) = 1.088 ± 0.009 ± 0.004 (syst.)
- &tau(/\b)/&tau(B0) = 1.020 ± 0.030 ± 0.008 (syst.)
(Ratios Calculated using our lifetime measurements)
In terms of microns the results are
- c&tau(B+) = 491.4 ± 2.6(stat.) ± 2.6 (syst.) μm
- c&tau(B0) = 451.7 ± 3.0(stat.) ± 2.5 (syst.) μm
- c&tau(/\b) = 460.8 ± 13.4 (stat.) ± 4.1 (syst.) μm
Analysis Motivation and strategy
The lifetime of ground state hadrons containing a b quark and lighter quarks
is largely determined by the charged weak decay of the b quark. The spectator model which ignores the other quarks in the hadron, predicts equal lifetimes for all B hadrons. In reality, several effects change these lifetimes by up to about 10%.
Fully reconstructed B hadron decays with a J/&psi decaying to muon pairs in the final states are reconstructed in 4.3 fb-1. We use data collected by the dimuon trigger, which has no biasing effects on the observed proper time distribution. Signal samples of 45 thousand B+, 29 thousand B0and 1.7 thousand /\b are collected. The analysis consists of a maximum likelihood fit that uses information from mass, proper decay time and proper decay time error to extract the lifetime of the hadrons. The use of similar final states and a unified analysis strategy allow partial cancellation of certain systematic uncertainties in the lifetime ratios. The measured lifetimes and are the most precise determination of the B+, B0 and /\b lifetime.
A more detailed summary of the results can be found here:
pdf.
Below are the eps and gif versions of all figures meant for downloads.
- Figure 1: B+ mass (.eps)(.gif)
- Figure 2: fit - proper decay length projection (.eps)(.gif)
- Figure 3: B+ lifetime fit - proper decay length error projection (.eps)(.gif)
- Figure 4: B0 → J/&psi K*0 mass (.eps)(.gif)
- Figure 5: B0 → J/&psi K*0 lifetime fit - proper decay length projection (.eps)(.gif)
- Figure 6: B0 → J/&psi K*0 lifetime fit - proper decay length error projection (.eps)(.gif)
- Figure 7: B0 → J/&psi K0s mass (.eps)(.gif)
- Figure 8: B0 → J/&psi K0s lifetime fit - proper decay length projection (.eps)(.gif)
- Figure 9: B0 → J/&psi K0s lifetime fit - proper decay length error projection (.eps)(.gif)
- Figure 10: /\b mass (.eps)(.gif)
- Figure 11: /\b lifetime fit - proper decay length projection (.eps)(.gif)
- Figure 12: /\b lifetime fit - proper decay length error projection (.eps)(.gif)
Comparison plots (Note: the world average values do not include the CDF preliminary results that are presented here):
- Figure 13: B+ lifetime (.png)
- Figure 14: B0 lifetime (.png)
- Figure 15: B+ / B0 lifetime ratio (.png)
- Figure 16: /\b (.png)
Further Plots: Sideband projections and residuals
- Figure 17: B+ fit - proper decay length projection sideband (.eps)(.gif)
- Figure 18: B+ lifetime fit - proper decay length error projection sideband(.eps)(.gif)
- Figure 19: B+ fit - proper decay length projection sideband residual (.eps)(.gif)
- Figure 20: B+ lifetime fit - proper decay length projection residual(.eps)(.gif)
- Figure 21: B0 → J/&psi K*0 fit - proper decay length projection sideband (.eps)(.gif)
- Figure 22: B0 → J/&psi K*0 lifetime fit - proper decay length error projection sideband(.eps)(.gif)
- Figure 23: B0 → J/&psi K*0 fit - proper decay length projection sideband residual (.eps)(.gif)
- Figure 24: B0 → J/&psi K*0 lifetime fit - proper decay length projection residual(.eps)(.gif)
- Figure 25: B0 → J/&psi K0sfit - proper decay length projection sideband (.eps)(.gif)
- Figure 26: B0 → J/&psi K0s lifetime fit - proper decay length error projection sideband(.eps)(.gif)
- Figure 27: B0 → J/&psi K0sfit - proper decay length projection sideband residual (.eps)(.gif)
- Figure 28:B0 → J/&psi K0s lifetime fit - proper decay length projection residual(.eps)(.gif)
- Figure 29: /\b fit - proper decay length projection sideband (.eps)(.gif)
- Figure 30: /\b lifetime fit - proper decay length error projection sideband(.eps)(.gif)
- Figure 31: /\b fit - proper decay length projection sideband residual (.eps)(.gif)
- Figure 32: /\b lifetime fit - proper decay length projection residual(.eps)(.gif)
