Speaker
Description
Author and Presenter: Oleksandr Tomalak
Abstract: We study radiative corrections to low-energy charged-current processes involving nucleons, such as neutron beta decay and (anti)neutrino-nucleon scattering within a top-down effective-field-theory approach. First, we match the Standard Model to the low-energy effective theory valid below the weak scale, specifying the scheme dependence of the Wilson coefficients. We evolve the resulting effective coupling down to the hadronic scale using renormalization group equations. To evaluate radiative corrections at scales of the neutron decay, we perform matching to heavy-baryon chiral perturbation theory and subsequently, below the pion-mass scale, to a pionless effective theory, evolving the effective couplings all the way down to the scale of the electron mass, relevant for beta decay. We provide a representation for hadronic corrections in terms of infrared finite convolutions of simple kernels with the single-nucleon matrix elements of time-ordered products of two and three quark bilinears (vector, axial-vector, and pseudoscalar). Using our new result for the radiative corrections, we update the extraction of the largest Cabibbo-Kobayashi-Maskawa matrix element Vud from the neutron decay.
I also refine the treatment of hadronic uncertainties in low-energy neutral-current processes, significantly reducing the current error estimate. These improvements have direct implications for all neutral-current interactions at low energies, including parity-violating electron scattering, elastic (anti)neutrino-electron scattering, coherent elastic (anti)neutrino-nucleus scattering, and atomic parity violation.
