Family nonuniversal<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>Z</mml:mi><mml:mo>′</mml:mo></mml:msup></mml:math>models with protected flavor-changing interactions

Abstract

We define a new class of ${Z}^{\ensuremath{'}}$ models with neutral flavor-changing interactions at tree level in the down-quark sector. They are related in an exact way to elements of the quark mixing matrix due to an underlying flavored ${\mathrm{U}(1)}^{\ensuremath{'}}$ gauge symmetry, rendering these models particularly predictive. The same symmetry implies lepton-flavor nonuniversal couplings, fully determined by the gauge structure of the model. Our models allow us to address presently observed deviations from the standard model and specific correlations among the new physics contributions to the Wilson coefficients ${C}_{9,10}^{(\ensuremath{'})\ensuremath{\ell}}$ can be tested in $b\ensuremath{\rightarrow}s{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ transitions. We furthermore predict lepton-universality violations in ${Z}^{\ensuremath{'}}$ decays, testable at the LHC.