Test of the Pauli Exclusion Principle in the VIP-2 Underground Experiment

C Curceanu ,S Bertolucci ,S Bartalucci ,M Iliescu ,L De Paolis ,H Shi ,A Scordo ,A Pichler ,M Miliucci ,D Sirghi ,S Di Matteo ,E Widmann ,K Piscicchia ,C Berucci ,O Vázquez Doce ,M Laubenstein ,A Clozza ,J.‐P Egger ,M Bragadireanu ,C Guaraldo ,M Bazzi ,F Sirghi ,D Pietreanu ,J Márton ,E Milotti ,L Sperandio ,M Cargnelli ,J Zmeskal

doi:10.3390/e19070300

Abstract

The validity of the Pauli exclusion principle—a building block of Quantum Mechanics—is tested for electrons. The VIP (violation of Pauli exclusion principle) and its follow-up VIP-2 experiments at the Laboratori Nazionali del Gran Sasso search for X-rays from copper atomic transitions that are prohibited by the Pauli exclusion principle. The candidate events—if they exist—originate from the transition of a 2 p orbit electron to the ground state which is already occupied by two electrons. The present limit on the probability for Pauli exclusion principle violation for electrons set by the VIP experiment is 4.7 × 10 − 29 . We report a first result from the VIP-2 experiment improving on the VIP limit, which solidifies the final goal of achieving a two orders of magnitude gain in the long run.

Highlights

The Pauli exclusion principle (PEP) states that in a system there cannot be two fermions with all quantum numbers identical, and is a fundamental principle in physics
In order to obtain the number of events violating PEP in the ROI, the current-on spectrum was normalized to 28 days of data collection time, and a subtraction with the current-off spectrum was performed
The first VIP-2 physics run from two months of data collection already gave a better limit than the VIP result obtained from three years of running

Summary

Introduction

The Pauli exclusion principle (PEP) states that in a system there cannot be two (or more) fermions with all quantum numbers identical, and is a fundamental principle in physics. Messiah and Greenberg noted in [2] that this superselection rule “does not appear as a necessary feature of the QM description of nature” In this context, the violation of PEP is equivalent to the violation of spin-statistics [3], and experimentally to the existence of states of particles that follow statistics other than the fermionic or the bosonic ones. Particles that are neither fermions nor bosons, and that may exist in electronic systems confined to two spatial dimensions have been constructed theoretically and investigated in the laboratory with great consistency with the theories as reviewed in [8] The physics of this special system is exciting in itself and may provide hints to the searches for the violation of the PEP in other systems.

VIP-2 Experiment

First VIP-2 Results

Conclusions and Future Perspectives