On V_ud determination from neutron decay
  The recent results of the PIBETA experiment strongly suggest the presence of a non-(V-A) anomalous interaction in the radiative pion decay. The same interaction should inevitably contribute to the neutron decay and in particular it should affect the V_ud determination. This paper is dedicated to the prediction of the eventual discrepancy in V_ud extracted from the super-allowed Fermi transitions and from the polarized neutron decay. 
M. V. Chizhov