An experimental program with high duty-cycle polarized and unpolarized positron beams at Jefferson Lab

TL;DR

This paper discusses the development and potential applications of high duty-cycle polarized and unpolarized positron beams at Jefferson Lab, emphasizing their importance for advanced nuclear and particle physics experiments.

Contribution

It presents the experimental program and prospects for high duty-cycle positron beams at JLab, highlighting their role in nuclear structure studies and Standard Model tests.

Findings

Positron beams are crucial for precise nucleon structure measurements.

High duty-cycle positron beams enable advanced scattering experiments.

Potential for new physics searches like dark photons and lepton flavor violation.

Abstract

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.