Updates of Semileptonic Results for Lepton-Photon 2005

The changes of this update with respect to the previous status are described here. A writeup will be produced after the summer conference season for publication as hep-ex.

A spreadsheet with the breakdown of the errors is available.

For averages not shown here see http://www.slac.stanford.edu/xorg/hfag/semi/winter05/winter05.shtml
Inclusive Vub average for Lepton-Photon 2005

|Vub| in inclusive semileptonic B decays

The results in this section are determined by comparing the measured partial branching fractions to theoretical calculations of the corresponding rates, which are proportional to |Vub|2. The theoretical calculation is from Bosch, Lange, Neubert and Paz, documented in hep-ph/0504071. Only measurements at the Upsilon(4S), i.e. from the BABAR, BELLE, and CLEO collaborations are used in performing the average. Several different sources of input for the heavy quark parameters mb and mupi2 are considered below; at this point in time the choice of which input is "most reliable" is still a matter of debate. The contours in the mb.vs.mupi2 plane for the different choices shown below can be seen in this plot. In addition, a comparison showing the separate fits to only b -> c l nu moments and only b -> s gamma moments can be found here.

The procedure for performing the average is documented in a brief note on averaging. There have been several changes from what was done in previous HFAG semileptonic averages.

The input files for the average are linked below. To summarize briefly, all theoretical uncertainties are considered to be correlated, as are the uncertainties on the modeling of b -> clnu and b -> ulnu decays. Experimental uncertainties (particle identification, reconstruction efficiencies, etc.) are taken as correlated amongst measurements from the same experiment, but not correlated across experiments. The set of results averaged have negligeable statistical correlations. Variations on the assumptions of which experimental errors were taken as correlated were considered; they have no significant impact on the average. If one fails to account for the dependence of the quoted errors on the measured values, the resulting average is biased low by -0.3 sigma.

The errors in the tables are experimental (statistical and systematic) and external (theoretical and HQ parameter uncertainties). The average B lifetime used was 1.604 ps. Vub with HQ parameters from b -> c l nu and b -> s g moments

|Vub| with HQ parameters from b -> c l nu and b -> s g moments

The following values use HQ parameter input from a global fit to both b -> c l nu and b -> s g moments in the kinetic scheme, which gives parameters mb = 4.60 +- 0.04 GeV and mupi2=0.20 +- 0.04 GeV2 (hep-ph/0507253). The details of the fit are here.

These results are similar to those obtained in the 1S scheme in Phys. Rev. D70:094017, 2004 ( hep-ph/0408002). Work is in progress in HFAG to update the 1S fits using the latest set of moments measurements.

Experiment Value [10-3] Parameters References Remarks
CLEO (endpoint) 3.93 +/- 0.46 +/- 0.33 input Phys.Rev.Lett.88:231803,2002 2.1 < p < 2.6, Vub redetermined from partial BF
BELLE (endpoint) 4.82 +/- 0.45 +/- 0.31 input preliminary (hep-ex/0504046) 1.9 < p < 2.6
BABAR (endpoint) 4.20 +/- 0.34 +/- 0.30 input preliminary (hep-ex/0408075) 2.0 < p < 2.6, Vub redetermined from partial BF
BABAR (E_{e}, q^{2}) 4.00 +/- 0.27 +/- 0.35 input preliminary (hep-ex/0506036) (Ee-q2)
BELLE m_{X} 4.03 +/- 0.27 +/- 0.25 input preliminary (hep-ex/0505088) mX, BRECO tag; other methods (mX-q2 and P not used)
BELLE sim. ann. (m_{X}, q^{2}) 4.32 +/- 0.46 +/- 0.29 input Phys.Rev.Lett.92:101801,2004 (hep-ex/0311048) mX - Q2, tag with annealing method
BABAR (m_{X}, q^{2}) 4.70 +/- 0.34 +/- 0.31 input preliminary (hep-ex/05NNNNN) mX-q2, BRECO tag
Average +/- exp +/- (mb,theory) 4.39 +/- 0.20 +/- 0.27 chi2/dof = 6.4/6 (CL = 0.38) Plots: eps gif HQ parameter input from b to c l nu and b to s gamma moments
The full breakdown of the uncertainties on the average |Vub| above is (all errors quoted in percent):

+-2.3stat +-2.5exp +-2.1b2c model +-2.1b2u model +-4.5HQ param +-3.6sub SF +-1.9WA = +-7.5tot

where the errors correspond to statistics, experimental systematics, the modeling of b -> c l nu and b -> u l nu decays, the HQ parameters mb and mupi2, subleading shape functions and Weak Annihilation.

Inclusive Vub average, LP2005, using only b -> c l nu input

|Vub| using only b -> c l nu moments as input for HQ parameters

The numbers below use input on the heavy quark parameters mb and mupi2 from based on global fits to b -> c l nu moments in the kinetic scheme, translated into the shape-function mass scheme to give mb = 4.66 +- 0.08 GeV mupi2=0.19 +- 0.05 GeV2 with correlation rho=-0.4. The details of the fit are here.

Experiment Value [10-3] Parameters References Remarks
CLEO (endpoint) 3.61 +/- 0.42 +/- 0.47 input Phys.Rev.Lett.88:231803,2002 2.1 < p < 2.6, Vub redetermined from partial BF
BELLE (endpoint) 4.52 +/- 0.42 +/- 0.43 input preliminary (hep-ex/0504046) 1.9 < p < 2.6
BABAR (endpoint) 3.87 +/- 0.31 +/- 0.43 input preliminary (hep-ex/0408075) 2.0 < p < 2.6, Vub redetermined from partial BF
BABAR (E_{e}, q^{2}) 3.70 +/- 0.25 +/- 0.49 input preliminary (hep-ex/0506036) (Ee-q2)
BELLE m_{X} 3.81 +/- 0.25 +/- 0.36 input preliminary (hep-ex/0505088) mX, BRECO tag; other methods (mX-q2 and P not used)
BELLE sim. ann. (m_{X}, q^{2}) 4.11 +/- 0.43 +/- 0.40 input Phys.Rev.Lett.92:101801,2004 (hep-ex/0311048) mX - Q2, tag with annealing method
BABAR (m_{X}, q^{2}) 4.47 +/- 0.32 +/- 0.43 input preliminary (hep-ex/0507017) mX-q2, BRECO tag
Average +/- exp +/- (mb,theory) 4.23 +/- 0.20 +/- 0.39 chi2/dof = 4.5/6 (CL = 0.61) Plots: eps gif HQ parameter input from b to c l nu moments only
The full breakdown of the uncertainties on the average |Vub| above is (all errors quoted in percent):

+-2.5stat +-2.5exp +-2.3b2c model +-2.0b2u model +-8.2HQ param +-3.7sub SF +-1.8WA = +-10.3tot

where the errors correspond to statistics, experimental systematics, the modeling of b -> c l nu and b -> u l nu decays, the HQ parameters mb and mupi2, subleading shape functions and Weak Annihilation.

B -> pi l nu average for Lepton-Photon 2005

Branching fractions of B -> pi l nu and determination of Vub

The measurements quoted here include both B0 and B+ decays; the average assumes equality of the semileptonic decays widths for these isospin-conjugate states, and is quoted for B0 decays.

Experiment / Mode BF [10-4] BF(q2>16 GeV2) [10-4] Reference
BABAR SL tag: B ^{+} \rightarrow \pi^{0} l^{+} \nu \times 2\tau_{0}/\tau_{+} 3.31 +/- 0.68 +/- 0.42 NA (1.80+-0.37+-0.23) Preliminary, SL tag (hep-ex/0506065) (input)
BABAR Breco tag: B ^{+} \rightarrow \pi^{0} l^{+} \nu \times 2\tau_{0}/\tau_{+} 1.68 +/- 0.52 +/- 0.24 NA (0.91+-0.28+-0.14) Preliminary, Breco tag (ICHEP conference paper) (input)
BABAR SL tag: B ^{0} \rightarrow \pi^{-} l^{+} \nu 1.02 +/- 0.25 +/- 0.13 0.21 +/- 0.14 +/- 0.06 Preliminary, SL tag (hep-ex/0506064) (input)
Belle SL tag: B ^{0} \rightarrow \pi^{-} l^{+} \nu 1.79 +/- 0.28 +/- 0.20 +/- 0.03 0.46 +/- 0.17 preliminary, SL tag (hep-ex/0408145) (input)
BABAR Breco tag: B ^{0} \rightarrow \pi^{-} l^{+} \nu 0.89 +/- 0.34 +/- 0.12 NA Preliminary, Breco tag (ICHEP conference paper) (input)
CLEO untagged: B \rightarrow \pi l^{+} \nu 1.32 +/- 0.18 +/- 0.11 0.25 +/- 0.09 +/- 0.05 Phys. Rev. D 68, 072003 (2003) (input)
BABAR untagged: B \rightarrow \pi l^{+} \nu 1.38 +/- 0.10 +/- 0.18 0.49 +/- 0.05 +/- 0.07 Preliminary, nu reco (CKM2005 workshop talk) (input)
Average: B ^{0} \rightarrow \pi^{-} l^{+} \nu 1.36 +/- 0.11 0.396 +/- 0.054 Plots: eps gif   chi2/dof = 11.2/6 (CL = 0.083)

Using the partial BF for q2> 16 GeV2 and the FNAL04 calculation (hep-lat/0409116) of the form factor gives |Vub| = (3.75 +/- 0.27 +0.64 -0.42) 10-3, where the first error is experimental and the second due to the normalization unceratainty in the form factor calculation. With the HPQCD calculation (hep-lat/0408019) of the form factor, |Vub| = (4.45 +/- 0.32 +0.69 -0.47) 10-3.

A determination of |Vub| using the region at low q2 along with LCSR calculations is in progress, as is the use of methods that use the full q2 range. nada

Branching fractions of other exclusive charmless semileptonic decays

Experiment Mode BF [10-4] Reference
CLEO B+-> eta l+ nu 0.84 +/-0.31 +0.16 +/-0.09 Phys. Rev. D 68, 072003 (2003)
CLEO B0-> rho- l+ nu 2.69 +/-0.41 +0.35/-0.40 +/-0.50 Phys. Rev. D 61, 052001 (2000)
BABAR B0-> rho- l+ nu 2.57 +/-0.52 +/-0.59 Preliminary, Breco tag (ICHEP conference paper)
BABAR B0-> rho- l+ nu 3.29 +/-0.42 +/-0.47 +/-0.60 Phys. Rev. Lett. 90, 181801 (2003)
CLEO B0-> rho- l+ nu 2.17 +/-0.34 +0.47/-0.54 +/-0.41 +/-0.01 Phys. Rev. D 68, 072003 (2003)
Belle B0-> rho- l+ nu 2.54 +/-0.78 +/-0.85 +/-0.30 preliminary (hep-ex/0408145)
BABAR B0-> rho- l+ nu 2.14 +/-0.21 +/-0.51 +/-0.28 Preliminary, nu reco (CKM2005 workshop talk)
Belle B+-> omega l+ nu 1.3 +/-0.4 +/-0.2 +/-0.3 Phys. Rev. Lett. 93:131803 (2004)

Last update: 2005/06/29 Bob Kowalewski