## Abstract

Present precision measurements of the neutron lifetime lead to a CKM matrix element |V_{ud}|, which is 3 standard deviations off the value inferred from heavy quark decays, etc. We investigate the possibility whether isospin-breaking effects in the neutron-to-proton vector current transition matrix element <p|V^{+}_{0}|n>= 1 + δg_{V} could eventually close this gap. For that we calculate in chiral perturbation theory the effect of pion and kaon loops on the matrix element <p|V^{+}_{0}|n> taking into account the mass differences of the charged and neutral mesons. We find a negligibly small isospin-breaking effect of δg_{V}≃ -4 × 10^{-5}. The crucial quantity in the analysis of neutron β-decay precision measurements is thus the radiative correction term Δ_{R}. Furthermore, we calculate in heavy baryon chiral perturbation theory the SU(3) breaking effects on the vector transition charges of weak semileptonic hyperon decays. We find for these quantities channel-dependent relative deviations from the SU(3) limit which range from -10% to + 1%.

Original language | English |
---|---|

Article number | 028201 |

Pages (from-to) | 282011-282014 |

Number of pages | 4 |

Journal | Physical Review C - Nuclear Physics |

Volume | 64 |

Issue number | 2 |

DOIs | |

State | Published - Aug 2001 |