Forbidden and invisible Z boson decays in a covariant θ-exact noncommutative standard model

The triple neutral gauge boson and direct U(1)Y-neutrino interactions, being absent in ordinary field theory, can arise quite naturally in noncommutative gauge field theories. Using non-perturbative methods and a Seiberg–Witten map-based covariant approach to noncommutative gauge theory, we have found θ-exact expressions for both interactions, thereby eliminating previous restrictions to low-energy phenomena. In particular, we obtain for the first time the covariant, θ-exact, triple neutral gauge boson interactions within the noncommutative standard model gauge sector including an additional gauge-field deformation freedom. Finally, we discuss implications for Z → γγ and Z→ ν-bar ν decays, and show that our results behave quite reasonably throughout all interaction energy scales. (paper)