APEX: A Prime EXperiment at Jefferson Lab

New York University, Department of Physics, 4 Washington Place, New York, NY 10003, USA

^a e-mail: j.beacham@cern.ch

Published online: 9 June 2014

Abstract

APEX is an experiment at Thomas Jefferson National Accelerator Facility (JLab) in Virginia, USA, that searches for a new gauge boson (A^′) with sub-GeV mass and coupling to ordinary matter of g^′ ∼ (10⁻⁶ − 10⁻²)e. Electrons impinge upon a fixed target of high-Z material. An A^′ is produced via a process analogous to photon bremsstrahlung, decaying to an e⁺e⁻ pair. A test run was held in July of 2010, covering m_A^′ = 175 to 250 MeV and couplings g^′/e > 10⁻³. A full run is approved and will cover m_A^′ ∼65 to 525 MeV and g^′/e > 2.3 × 10⁻⁴.