Updates of Semileptonic Results for EPS 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 and EPS, summer 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 Delta-chi2=1 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

These results are similar to those prepared for Lepton-Photon 2005; some minor errors in the input files and typos in the html were fixed, which is why the values are slightly changed.

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 with correlation coefficient -0.26 (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) 4.02 +/- 0.47 +/- 0.35 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 Phys.Lett.B621:28-40 (2005) (hep-ex/0504046) 1.9 < p < 2.6
BABAR (endpoint) 4.23 +/- 0.27 +/- 0.31 input preliminary (hep-ex/0408075) 2.0 < p < 2.6, Vub redetermined from partial BF
BABAR (E_{e}, q^{2}) 4.06 +/- 0.27 +/- 0.36 input submitted to PRL (hep-ex/0506036) (Ee-q2)
BELLE m_{X} 4.08 +/- 0.27 +/- 0.25 input submitted to PRL (hep-ex/0505088) mX, BRECO tag; other methods (mX-q2 and P not used)
BELLE sim. ann. (m_{X}, q^{2}) 4.38 +/- 0.46 +/- 0.30 input Phys.Rev.Lett.92:101801,2004 (hep-ex/0311048) mX - Q2, tag with annealing method
BABAR (m_{X}, q^{2}) 4.76 +/- 0.34 +/- 0.32 input preliminary (hep-ex/0507017) mX-q2, BRECO tag
Average +/- exp +/- (mb,theory) 4.38 +/- 0.19 +/- 0.27 chi2/dof = 5.9/6 (CL = 0.43) 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):

+-2.2stat +-2.5exp +-1.9b2c model +-2.2b2u model +-4.7HQ param +-3.5sub SF +-1.9WA = +-7.6tot

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. No uncertainty is assigned for possible duality violations.

Using the average |Vub| along with the calculated full b -> u l nu rate from BLNP (70.8/ps-1/|Vub|2) results in a total BF

BF(b -> u l nu) = (2.18 +- 0.33)*10-3

B -> pi l nu average for EPS 2005

Branching fractions of B -> pi l nu

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] 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 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_{+} 1.45 +/- 0.37 +/- 0.12 0.99 +/- 0.31 +/- 0.09 0.46 +/- 0.20 +/- 0.04 (0.79+-0.20+-0.11) preliminary Breco tag (hep-ex/0507085) (input)
BELLE SL tag: B ^{+} \rightarrow \pi^{0} l^{+} \nu \times 2\tau_{0}/\tau_{+} 1.40 +/- 0.24 +/- 0.16 0.99 +/- 0.20 +/- 0.12 0.41 +/- 0.15 +/- 0.04 (0.76+-0.13+-0.09) Preliminary, SL tag, presented at EPS 2005, Lisbon (input)
BABAR SL tag: B ^{0} \rightarrow \pi^{-} l^{+} \nu 1.02 +/- 0.25 +/- 0.13 0.81 +/- 0.22 +/- 0.11 0.21 +/- 0.14 +/- 0.05 Preliminary, SL tag (hep-ex/0506064) (input)
BELLE SL tag: B ^{0} \rightarrow \pi^{-} l^{+} \nu 1.48 +/- 0.20 +/- 0.16 1.08 +/- 0.16 +/- 0.12 0.40 +/- 0.12 +/- 0.05 preliminary, SL tag, presented at EPS 2005, Lisbon (input)
BABAR Breco tag: B ^{0} \rightarrow \pi^{-} l^{+} \nu 1.24 +/- 0.29 +/- 0.16 0.54 +/- 0.19 +/- 0.06 0.70 +/- 0.22 +/- 0.11 Preliminary, Breco tag, (hep-ex/0507085) (input)
CLEO untagged: B \rightarrow \pi l^{+} \nu 1.32 +/- 0.18 +/- 0.13 1.07 +/- 0.16 +/- 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 0.89 +/- 0.09 +/- 0.12 0.49 +/- 0.05 +/- 0.06 Untagged, submitted to PRD-RC (hep-ex/0507003) (input)
Average: B ^{0} \rightarrow \pi^{-} l^{+} \nu 1.35 +/- 0.08 +/- 0.08 0.89 +/- 0.06 +/- 0.06 0.40 +/- 0.04 +/- 0.04 Plots: eps gif   chi2/dof = 8.0/7 (CL = 0.33)

Vub from B -> pi l nu average for EPS 2005

Exclusive Vub determination

The partial BF quoted above along with theoretical calculations of the form factor normalization can be used to determine Vub; a few recent calculations are shown below. Note that the FNAL04 and HPQCD unquenched LQCD calculations are not entirely independent. The Ball-Zwicky calculation is based on light-cone sum rules. At this time we do not attempt to average the Vub results or select a best value.

A determination of |Vub| making use of the experimental input on the q2 dependence is under study but not yet available.

The errors on |Vub| are experimental and theoretical, respectively.

FF calculation Vub [10-3] q2 range FF norm (ps-1) Reference
Ball-Zwicky full q2 3.37 +/- 0.14 +0.66-0.41 full 7.74 +/- 2.32 Phys. Rev. D71:014015 (2005)
HPQCD full q2 3.93 +/- 0.17 +0.77-0.48 full 5.70 +/- 1.71 hep-lat/0408019
FNAL full q2 3.76 +/- 0.16 +0.87-0.51 full 6.24 +/- 2.12 hep-lat/0409116
Ball-Zwicky q2 < 16 3.27 +/- 0.16 +0.54-0.36 <16 GeV2 5.44 +/- 1.43 Phys. Rev. D71:014015 (2005)
HPQCD q2 > 16 4.47 +/- 0.30 +0.67-0.46 >16 GeV2 1.31 +/- 0.32 hep-lat/0408019
FNAL q2 > 16 3.78 +/- 0.25 +0.65-0.43 >16 GeV2 1.83 +/- 0.50 hep-lat/0409116

A plot of this table is available in two formats: eps gif

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)
BABAR B0-> rho- l+ nu 2.14 +/-0.21 +/-0.51 +/-0.28 Untagged, submitted to PRD-RC (hep-ex/0507003)
BELLE B0-> rho- l+ nu 2.07 +/-0.47 +/-0.25 +/-0.14 preliminary (Talk presented at EPS 2005, Lisbon)
BELLE B+-> rho0 l+ nu 1.39 +/-0.23 +/-0.17 +/-0.02 preliminary (Talk presented at EPS 2005, Lisbon)
BELLE B+-> omega l+ nu 1.3 +/-0.4 +/-0.2 +/-0.3 Phys. Rev. Lett. 93:131803 (2004)

Last update: 2005/08/24 Bob Kowalewski