APEX: A Prime EXperiment at Jefferson Lab

TL;DR

APEX is an experiment at Jefferson Lab designed to search for a new light gauge boson ($A'$) within specific mass and coupling ranges, utilizing electron fixed-target collisions to detect potential signals of new physics beyond the Standard Model.

Contribution

This paper introduces the APEX experiment, detailing its design, initial test run results, and planned full run parameters for searching for a new gauge boson.

Findings

Test run covered $m_{A'}$ = 175-250 MeV and $g'/e > 10^{-3}$.

Full run aims to cover $m_{A'}$ = 65-525 MeV and $g'/e > 2.3 imes 10^{-4}$.

Experiment sets new constraints on light gauge boson parameter space.

Abstract

APEX is an experiment at Thomas Jefferson National Accelerator Facility (JLab) in Virginia, USA, that searches for a new gauge boson ($A^\prime$) with sub-GeV mass and coupling to ordinary matter of $g^\prime \sim (10^{-6} - 10^{-2}) e$. Electrons impinge upon a fixed target of high-Z material. An $A^\prime$ 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 $m_{A^\prime}$ = 175 to 250 MeV and couplings $g^\prime/e \; \textgreater \; 10^{-3}$. A full run is approved and will cover $m_{A^\prime} \sim$ 65 to 525 MeV and $g^\prime/e \; \textgreater \; 2.3 \times10^{-4}$.