80 research outputs found
Radiative Corrections and the Universality of the Weak Interactions
We review the radiative corrections to superallowed Fermi transitions and
neutron beta decay in the Standard Model, and their relevance for the
universality of the Weak Interactions.Comment: 5 pages. Invited talk at 8th Conference on the Intersections of
Particle and Nuclear Physics (CIPANP 2003), New York, New York, 19-24 May
200
Considerations concerning the generalization of the Dirac equations to unstable fermions
We discuss the generalization of the Dirac equations and spinors in momentum
space to free unstable spin- fermions taking into account the fundamental
requirement of Lorentz covariance. We derive the generalized adjoint Dirac
equations and spinors, and explain the very simple relation that exists, in our
formulation, between the unstable and stable cases. As an application of the
generalized spinors, we evaluate the probability density. We also discuss the
behavior of the generalized Dirac equations under time reversal.Comment: 7 pages, matches journal versio
Improved Calculation of Electroweak Radiative Corrections and the Value of V_ud
A new method for computing hadronic effects on electroweak radiative
corrections to low-energy weak interaction semileptonic processes is described.
It employs high order perturbative QCD results originally derived for the
Bjorken sum rule along with a large N QCD-motivated interpolating function that
matches long and short-distance loop contributions. Applying this approach to
the extraction of the CKM matrix element V_ud from superallowed nuclear beta
decays reduces the theoretical loop uncertainty by about a factor of 2 and
gives V_ud = 0.97377(11)(15)(19). Implications for CKM unitarity are briefly
discussed.Comment: 12 pages, no figures. Ref. [8] correcte
- …