This web page summarizes the results for the measurement of the B⁺ Lifetime performed using the decay channel B⁺ → D⁰&pi⁺ based upon 1.0 fb^-1 of data.
The results have been approved as of 12th June 2008.
We find a total of 24200 ± 200 signal events. This measurement has been made using data from an impact parameter based trigger which intrinsically biases the lifetime distribution. This is the first measurement to correct for this bias without use of information from detailed Monte Carlo simulation, using instead information from the decay kinematics to correct for the bias on an event by event basis. The benefits of using a simulation free method is that the systematic errors are not dominated by uncertainties in the MC. This method of lifetime measurement is applicable to future experiments that also have an impact parameter based trigger and this measurement is a demonstration that such a method is viable.

We measure:

• &tau(B⁺) = 1.662 ± 0.023 (stat.) ± 0.015 (syst.) ps

A more detailed summary of the results can be found here: pdf.

• Figure 1: B⁺ mass projection(.eps)(.gif)
• Figure 2: B⁺ lifetime fit - proper decay length projection (.eps)(.gif)
• Figure 3: B⁺ Fisher scalar variable, distribution in data(.eps)(.gif)
• Figure 4: B⁺ Signal fraction vs fisher scalar. Fit projection and comparison to signal fraction determined by mass fits. This plot demonstrates that the function returned by fit really is a good measure of signal fraction, as it compares well to the signal fraction determined by mass fit using events in that particular bin of fisher scalar. (.eps)(.gif)


• Figure 5: B⁺ Difference in acceptance function between signal and background in data (.eps)(.gif)
• Figure 6: First diagram detailing acceptance function calculation (.pdf)
• Figure 7: Second diagram detailing acceptance function calculation (.pdf)
• Table 1: Systematic error table. (.pdf(microns))(.pdf(picosec)(.tex)