https://doi.org/10.1140/epjc/s10052-014-3226-3
Regular Article - Experimental Physics
Determination of 
and extraction of 
from semileptonic 
decays
Institute of High Energy Physics, Beijing, 100039, People’s Republic of China
* e-mail: fangy@ihep.ac.cn
Received:
29
September
2014
Accepted:
11
December
2014
Published online:
14
January
2015
By globally analyzing all existing measured branching fractions and partial rates in different four momentum transfer-squared 
bins of 
decays, we obtain the product of the form factor and magnitude of Cabibbo–Kobayashi–Maskawa matrix element 
to be 
. With this product, we determine the 
semileptonic form factor 
in conjunction with the value of determined from the standard model global fit. Alternately, with the product together with the input of the form factor calculated in lattice quantum chromodynamics (LQCD) recently, we extract 
, where the error is still dominated by the uncertainty of the form factor calculated in LQCD. Combining the 
extracted from all existing measurements of 
decays and together, we find the most precisely determined to be 
, which improves the accuracy of the PDG’2014 value 
by 
.
© SIF and Springer-Verlag Berlin Heidelberg, 2015
