${\it V}_{\it cb}$ MEASUREMENTS

For the discussion of ${\it V}_{\it cb}$ measurements, which is not repeated here, see the review on “Determination of $\vert {\it V}_{\it cb}\vert $ and $\vert {\it V}_{\it ub}\vert $.''
The CKM matrix element $\vert {\it V}_{\it cb}\vert $ can be determined by studying the rate of the semileptonic decay ${{\mathit B}}$ $\rightarrow$ ${{\mathit D}}{}^{(*)}$ ${{\mathit \ell}}{{\mathit \nu}}$ as a function of the recoil kinematics of ${{\mathit D}}{}^{(*)}$ mesons. Taking advantage of theoretical constraints on the normalization and a linear $\omega ~$dependence of the form factors ($\mathit F(\omega $), $\mathit G(\omega $)) provided by Heavy Quark Effective Theory (HQET), the $\vert {\it V}_{\it cb}\vert {\times }\mathit F(\omega $) and $\rho {}^{2}$ can be simultaneously extracted from data, where $\omega $ is the scalar product of the two-meson four velocities, $\mathit F$(1) is the form factor at zero recoil ($\omega $=1) and $\rho {}^{2}$ is the slope. Using the theoretical input of $\mathit F$(1), a value of $\vert {\it V}_{\it cb}\vert $ can be obtained.

$\vert {\it V}_{\it cb}\vert $ ${\times }$ $\mathit G$(1) (from ${{\mathit B}}$ $\rightarrow$ ${{\mathit D}^{-}}{{\mathit \ell}^{+}}{{\mathit \nu}}$)

INSPIRE   JSON  (beta) PDGID:
S052CB2
VALUE ($ 10^{-2} $) DOCUMENT ID TECN  COMMENT
$\bf{ 4.121 \pm0.100}$ OUR EVALUATION  $~~$(Produced by HFLAV) with ${{\mathit \rho}^{2}}=1.128$ $\pm0.033$ and a correlation 0.747. The fitted ${{\mathit \chi}^{2}}$ is 4.8 for 8 degrees of freedom.
$\bf{ 4.17 \pm0.08}$ OUR AVERAGE
$4.109$ $\pm0.116$ 1
LEES
2024
BABR ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \Upsilon}{(4S)}}$
$4.229$ $\pm0.137$ 2
GLATTAUER
2016
BELL ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \Upsilon}{(4S)}}$
$4.23$ $\pm0.19$ $\pm0.14$ 3
AUBERT
2010
BABR ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \Upsilon}{(4S)}}$
$4.31$ $\pm0.08$ $\pm0.23$ 4
AUBERT
2009A
 BABR ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \Upsilon}{(4S)}}$
$4.16$ $\pm0.47$ $\pm0.37$ 5
BARTELT
1999
CLE2 ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \Upsilon}{(4S)}}$
$2.78$ $\pm0.68$ $\pm0.65$ 6
BUSKULIC
1997
ALEP ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit Z}}$
• • We do not use the following data for averages, fits, limits, etc. • •
$4.11$ $\pm0.44$ $\pm0.52$ 7
ABE
2002E
 BELL Repl. by GLATTAUER 2016
$3.37$ $\pm0.44$ ${}^{+0.72}_{-0.49}$ 8
ATHANAS
1997
CLE2 Repl. by BARTELT 1999
1  Obtained from a 2D fit to the combined ${{\mathit B}}$ $\rightarrow$ ${{\overline{\mathit D}}}{{\mathit \ell}^{+}}{{\mathit \nu}_{{{{{\mathit \ell}}}}}}$ sample with a model-independent parametrization according to Boyd-Grinstein-Lebed (BGL), in which a hadronic decay of the second ${{\mathit B}}$ meson is fully reconstructed.
2  Obtained from a fit to the combined partially reconstructed ${{\mathit B}}$ $\rightarrow$ ${{\overline{\mathit D}}}{{\mathit \ell}}{{\mathit \nu}_{{{{{\mathit \ell}}}}}}$ sample while tagged by the other fully reconstructed ${{\mathit B}}$ meson in the event. Also reports fitted $\rho {}^{2}$ = $1.09$ $\pm0.05$.
3  Obtained from a fit to the combined ${{\mathit B}}$ $\rightarrow$ ${{\overline{\mathit D}}}{{\mathit \ell}^{+}}{{\mathit \nu}_{{{{{\mathit \ell}}}}}}$ sample in which a hadronic decay of the second ${{\mathit B}}$ meson is fully reconstructed and $\rho {}^{2}$ = $1.20$ $\pm0.09$ $\pm0.04$.
4  Obtained from a global fit to ${{\mathit B}}$ $\rightarrow$ ${{\mathit D}^{(*)}}{{\mathit \ell}}{{\mathit \nu}_{{{{{\mathit \ell}}}}}}$ events, with reconstructed ${{\mathit D}^{0}}{{\mathit \ell}}$ and ${{\mathit D}^{+}}{{\mathit \ell}}$ final states and $\rho {}^{2}$ = $1.20$ $\pm0.04$ $\pm0.07$.
5  BARTELT 1999: measured using both exclusive reconstructed ${{\mathit B}^{0}}$ $\rightarrow$ ${{\mathit D}^{-}}{{\mathit \ell}^{+}}{{\mathit \nu}}$ and ${{\mathit B}^{+}}$ $\rightarrow$ ${{\mathit D}^{0}}{{\mathit \ell}^{+}}{{\mathit \nu}}$ samples.
6  BUSKULIC 1997: measured using exclusively reconstructed ${{\mathit D}^{\pm}}$ with a $\mathit a{}^{2}=-0.05$ $\pm0.53$ $\pm0.38$. The statistical correlation is $0.99$.
7  Using the missing energy and momentum to extract kinematic information about the undetected neutrino in the ${{\mathit B}^{0}}$ $\rightarrow$ ${{\mathit D}^{-}}{{\mathit \ell}^{+}}{{\mathit \nu}}$ decay.
8  ATHANAS 1997: measured using both exclusive reconstructed ${{\mathit B}^{0}}$ $\rightarrow$ ${{\mathit D}^{-}}{{\mathit \ell}^{+}}{{\mathit \nu}}$ and ${{\mathit B}^{+}}$ $\rightarrow$ ${{\mathit D}^{0}}{{\mathit \ell}^{+}}{{\mathit \nu}}$ samples with a $\rho {}^{2}=0.59$ $\pm0.22$ $\pm0.12{}^{+0.59}_{-0}$. They report their experiment's uncertainties $\pm{}0.0044$ $\pm0.0048$ ${}^{+0.0053}_{-0.0012}$, where the first error is statistical, the second is systematic, and the third is the uncertainty due to the form factor model variations. We combine the last two in quadrature.
References