VIP 2: Experimental tests of the Pauli Exclusion Principle for electrons

TL;DR

VIP 2 aims to improve experimental constraints on the Pauli Exclusion Principle by using advanced detectors and shielding, with the goal of reducing the violation probability limit by two orders of magnitude.

Contribution

This paper reports on the development and testing of VIP 2, an improved experiment designed to test the Pauli Exclusion Principle with greater sensitivity.

Findings

Preliminary upper limit for PEP violation: 4.7 * 10^(-29)

Enhanced detector technology and shielding in VIP 2

Expected two-order improvement in violation probability limit

Abstract

The Pauli Exclusion Principle (PEP) was famously discovered in 1925 by the austrian physicist Wolfgang Pauli. Since then, it underwent several experimental tests. Starting in 2006, the VIP (Violation of the Pauli Principle) experiment looked for 2p to 1s X-ray transitions in copper, where 2 electrons are present in the 1s state before the transition happens. These transitions violate the PEP, and the lack of detection of the corresponding X-ray photons lead to a preliminary upper limit for the violation of the PEP of 4.7 * 10^(-29). The follow-up experiment VIP 2 is currently in the testing phase and will be transported to its final destination, the underground laboratory of Gran Sasso in Italy, in autumn 2015. Several improvements compared to its predecessor like the use of new X-ray detectors and active shielding from background gives rise to a goal for the improvement of the upper limit of the probability for the violation of the Pauli Exclusion Principle of 2 orders of magnitude.