Search for axion-like particles in the slac beam dump

Abstract

A search for axion-like particles was made at the Stanford Linear Accelerator Center (SLAC) by dumping 30 Coulombs of 20 GeV electrons into a beam absorption facility. After 179 meters of earth shielding the in-flight decay of the particle into two photons or an electron-positron pair, in a decay volume of 204 meters in length, was searched for with a fine-grained electromagnetic calorimeter. No positive signals were identified. Experimental limits were obtained for axions of mass up to ~ 200 MeV/c², and photinos of mass up to ~ 65 MeV/c².