https://doi.org/10.1140/epjc/s10052-008-0817-x
Regular Article - Theoretical Physics
Inclusive measure of |V ub | with the analytic coupling model
1
Dip. Fis., Univ. di Roma I “La Sapienza” & INFN Roma, Roma, Italy
2
Dep. of Phys., Queen Mary, University of London, London, UK
3
Dip. Fis., Univ. di Firenze & INFN Firenze, Sesto Fiorentino, Firenze, Italy
4
Dip. Scienze Fis., Univ. di Napoli “Federico II” & INFN Napoli, Napoli, Italy
* e-mail: ferrera@fi.infn.it
Received:
16
September
2008
Published online:
10
December
2008
By analyzing B→X
u
ℓ
ν
ℓ
spectra with a model based on soft-gluon resummation and an analytic time-like QCD coupling, we obtain 
where the first and the second error refer to experimental and theoretical error, respectively. This model successfully describes the accurate experimental data in beauty fragmentation, which has similar soft-gluon effects. The |V
ub
| value is obtained from the available measured semileptonic branching fractions in limited regions of the phase space. The distributions in the lepton energy E
ℓ
, the hadron invariant mass m
X
, the light-cone momentum
, together with the double distributions in (m
X
,q
2) and (E
ℓ
,s
h
max
), are used to select the phase-space regions. q
2 is the dilepton squared momentum and s
h
max
is the maximal m
X
2
at fixed q
2 and E
ℓ
. The |V
ub
| value obtained is in complete agreement with the value coming from exclusive B decays and from an over-all fit to the standard model parameters. We show that the slight disagreement (up to +2σ) with respect to previous inclusive measurements is not related to different choices for the b (and c) masses, but to a different modeling of the threshold (Sudakov) region.
© Springer-Verlag , 2009
