Eur. Phys. J. C (2018) 78: 319
https://doi.org/10.1140/epjc/s10052-018-5802-4

Regular Article - Experimental Physics

Experimental search for the violation of Pauli exclusion principle

VIP-2 Collaboration

¹ INFN, Laboratori Nazionali di Frascati, Via E. Fermi 40, Frascati, 00044, Rome, Italy
² Stefan-Meyer-Institut für Subatomare Physik, Boltzmanngasse 3, 1090, Wien, Austria
³ Dipartimento di Fisica, INFN-Sezione di Trieste, Università di Trieste, Via Valerio, 2, 34127, Trieste, Italy
⁴ Dipartimento di Fisica e Astronomia, Università di Bologna, Viale Berti Pichat 6/2, Bologna, Italy
⁵ IFIN-HH, Institutul National Pentru Fizica si Inginerie Nucleara Horia Hulubbei, Reactorului 30, Magurele, Romania
⁶ UMR 6251, IPR (Institut de Physique de Rennes), CNRS, Université de Rennes, 35000, Rennes, France
⁷ Institut de Physique, Université de Neuchâtel, 1 Rue A.-L. Breguet, 2000, Neuchâtel, Switzerland
⁸ Debye Institute for Nanomaterial Science, Utrecht University, P.O. Box 80.000 , 3508 TA, Utrecht, The Netherlands
⁹ INFN, Laboratori Nazionali del Gran Sasso, S.S. 17/bis, 67010, Assergi, AQ, Italy
¹⁰ Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi, Piazza del Viminale 1, 00183, Rome, Italy
¹¹ Excellence Cluster Universe, Technische Universität München, Boltzmannstraße 2, 85748, Garching, Germany
¹² Institut für Hochenergiephysik der Österreichischen Akademie der Wissenschaften, Nikolsdorfer Gasse 18, 1050, Wien, Austria

^* e-mail: Hexi.Shi@oeaw.ac.at

Received: 8 January 2018
Accepted: 12 April 2018
Published online: 20 April 2018

Abstract

The VIolation of Pauli exclusion principle -2 experiment, or VIP-2 experiment, at the Laboratori Nazionali del Gran Sasso searches for X-rays from copper atomic transitions that are prohibited by the Pauli exclusion principle. Candidate direct violation events come from the transition of a 2p electron to the ground state that is already occupied by two electrons. From the first data taking campaign in 2016 of VIP-2 experiment, we determined a best upper limit of for the probability that such a violation exists. Significant improvement in the control of the experimental systematics was also achieved, although not explicitly reflected in the improved upper limit. By introducing a simultaneous spectral fit of the signal and background data in the analysis, we succeeded in taking into account systematic errors that could not be evaluated previously in this type of measurements.