  Positron beams, both polarized and unpolarized, are identified as essential
ingredients for the experimental programs at the next generation of lepton
accelerators. In the context of the hadronic physics program at Jefferson Lab
(JLab), positron beams are complementary, even essential, tools for a precise
understanding of the electromagnetic structure of nucleons and nuclei, in both
the elastic and deep-inelastic regimes. For instance, elastic scattering of
polarized and unpolarized electrons and positrons from the nucleon enables a
model independent determination of its electromagnetic form factors. Also, the
deeply-virtual scattering of polarized and unpolarized electrons and positrons
allows unambiguous separation of the different contributions to the cross
section of the lepto-production of photons and of lepton-pairs, enabling an
accurate determination of the nucleons and nuclei generalized parton
distributions, and providing an access to the gravitational form factors.
Furthermore, positron beams offer the possibility of alternative tests of the
Standard Model of particle physics through the search of a dark photon, the
precise measurement of electroweak couplings, and the investigation of charged
lepton flavor violation. This document discusses the perspectives of an
experimental program with high duty-cycle positron beams at JLab.
