====== TTP04-13 Precision Measurements and CKM Unitarity ======
 
 
   <hidden TTP04-13  Precision Measurements and CKM Unitarity > Determinations of |Vud| and |Vus| along with their implications for the
 unitarity test |Vud|^2+|Vus|^2+|Vub|^2=1 are discussed. The leading two loop
 radiative corrections to neutron beta-decay are evaluated and used to derive a
 refined relationship |Vud|^2 tau_n (1+3g_A^2)=4908(4)sec. Employing |Vud|
 =0.9740(5) from superallowed nuclear decays and the measured neutron lifetime,
 tau_n = 885.7(7)sec leads to the precise prediction g_A=1.2703(8) which is
 compared with current direct experimental values. Various extractions of |Vus|
 are described and updated. The long accepted Particle Data Group value of |Vus|
 from fitted K_{e3} decay rates suggests a deviation from CKM unitarity but it
 is contradicted by more recent experimental results which confirm unitarity
 with good precision. An outlook for possible future advances is given.
 </hidden>
|**Andrzej Czarnecki, William J. Marciano, Alberto Sirlin**  | 
|**  Phys.Rev.  D70 093006 2004  **  |
| {{preprints:2004:ttp04-13.pdf|PDF}} {{preprints:2004:ttp04-13.ps|PostScript}} [[http://arxiv.org/abs/hep-ph/0406324|arXiv]]   |
| |