# VIP-2 with modulated current: pathfinder for enhanced Pauli exclusion principle violation studies

## TL;DR

The VIP-2 experiment tests if electrons can violate the Pauli Exclusion Principle by introducing a current in copper and analyzing X-ray signals.

## Contribution

A new analysis method using Discrete Fourier Transformation improves sensitivity to detect Pauli Exclusion Principle violations.

## Key findings

- A 1.5-fold improvement in sensitivity for detecting PEP violations was achieved using spectral analysis with Fourier transformation.
- The experiment ran for 68 days with modulated current in short 50-second intervals.
- X-ray emissions from copper were studied to detect potential PEP violations.

## Abstract

Fermions are subject to the Pauli Exclusion Principle (PEP), which is grounded on the spin-statistics theorem and, hence, related to the very same structure of the underlying symmetries. The VIP-2 (VIolation of Pauli exclusion principle - 2) experiment has been performing extreme sensitivity tests of the PEP, up to its current and final configuration, exploiting several experimental setups designed to study different theoretical models of PEP violation, looking for a faint signal of physics Beyond the Standard Model.A current is introduced in the copper target to bring new electrons into the system and, hence, fulfill the requirements of the Messiah-Greenberg Super-Selection rule. The searched spin-statistics violating signal corresponds to X-rays emitted when the new electrons perform atomic transitions to the already filled fundamental level of copper. This work analyzes the set of the VIP-2 data corresponding to a test run of 68 days in a current modulated regime alternating no current with current data-taking in short periods (50 s each), instead the usual alternating months-long data-taking of each of these two phases. We propose an analysis method to improve the experiment’s sensitivity: a spectral analysis constraint with the Discrete Fourier Transformation of the data. Compared to the spectrum-only analysis, about a factor of 1.5 of improvement to the limit for the probability of PEP violation for electrons was obtained.