Radiation Zeros in High-Energy $e^+e^-$ Annihilation into Hadrons

Abstract

The process $e^+e^- \to q \bar q γ$ contains radiation zeros, i.e. configurations of the four-momenta for which the scattering amplitude vanishes. We calculate the positions of these zeros for $u$--quark and $d$--quark production and assess the feasibility of identifying the zeros in experiments at high energies. The radiation zeros are shown to occur also for massive quarks, and we discuss how the $b \bar b γ$ final state may offer a particularly clean environment in which to observe them.