Testing the Pauli Exclusion Principle with accelerator mass spectrometry

We report the results of a new experimental search for the Pauli-forbidden 1s4 state of Be, denoted by Be′. Using the Accelerator Mass Spectrometer facility at Purdue, we set limits on the abundance of Be′ in metallic Be, Be ore, natural gas, and air (10−14). Our results improve on those obtained in a previous search for Be′ by a factor of approximately 300.