BABAR untagged B^{0}+B^{+} (6 q^{2} bins)
BABAR untagged B^{0}+B^{+} (12 q^{2} bins)
Belle untagged B^{0}
Belle hadronic tag B^{0} and B^{+}
In the first step of the averaging prodcedure, an average q^{2} spectrum is determined
from the measurements listed above. A plot of the average q^{2} spectrum can be found here:
pdf
The p-value for this average is 0.04.
The total branching fraction is then calculated from the sum
of the partial branching fractions in the average q^{2} spectrum,
taking the correlations between q^{2} bins into account.
Experiment / Mode | BF [10^{-4}] | Reference |
---|---|---|
Belle had. tag: B^{+} -> pi^{0} l^{+} nu × 2 τ_{0}/τ_{+} | 1.48 +/- 0.15 +/- 0.08 | Phys. Rev. D88, 032005 (2013) [arXiv:1306.2781 [hep-ex]] |
Belle had. tag: B^{0} -> pi^{-} l^{+} nu | 1.49 +/- 0.09 +/- 0.07 | Phys. Rev. D88, 032005 (2013) [arXiv:1306.2781 [hep-ex]] |
BABAR untagged (6 q^{2} bins): B -> pi l nu | 1.41 +/- 0.05 +/- 0.08 | Phys. Rev. D83, 032007 (2011) [arXiv:1005.3288v2 [hep/ex]] |
BABAR untagged (12 q^{2} bins): B -> pi l nu | 1.44 +/- 0.04 +/- 0.06 | Phys. Rev. D86, 092004 (2012) [arXiv:1201.1253 [hep/ex]] |
Belle untagged: B^{0} -> pi^{-} l^{+} nu | 1.48 +/- 0.04 +/- 0.07 | Phys. Rev. D83, 071101 (2011) [arXiv:1012.0090 [hep-ex]] |
Average: B^{0} -> pi^{-} l^{+} nu | 1.47 +/- 0.02 +/- 0.06 |
|V_{ub}| is determined from a combined fit of a B -> pi form factor parameterization to theory predictions and the average q^{2} spectrum in data.
The theory input included in the fit are the results from the FLAG lattice average (S. Aoki et al., [arXiv:1203.1359 [hep-ph]]) and the light-cone sum rule result at q^{2} = 0 GeV^{2} (A. Bharucha, JHEP 1205 (2012) 092 [arXiv:1203.1359 [hep-ph]]).
For the form factor parameterization, we use the BCL parameterization (Bourrely, Caprini and Lellouch, Phys. Rev. D79, 013008 (2009) [arXiv:0807.2722v3 [hep-ph]]) with 3+1 parameters, i.e. 3 parameters for the coefficients b_{0},b_{1},b_{2} in the BCL expansion and one normalization parameter for |V_{ub}|.
The results of the combined fit are:
|V_{ub}| = (3.65 +- 0.09 +- 0.11) × 10^{-3}
b_{0} = 0.421 +- 0.012
b_{1} = -0.390 +- 0.033
b_{2} = -0.650 +- 0.126
The quoted uncertainties on |V_{ub}| are experimental and theoretial, those on the BCL parameters are the combined experimental and theoretical errors obtained from the fit.
The probability of the fit is 0.61.
A plot of the fit result is available here: pdf