New experimental limits on the Pauli forbidden transitions in $^{12}$C nuclei obtained with 485 days Borexino data

TL;DR

This paper reports new experimental limits on violations of the Pauli exclusion principle in carbon-12 nuclei, using 485 days of Borexino data, setting the most stringent bounds to date on non-Paulian nuclear transitions.

Contribution

It provides the first and most stringent experimental bounds on PEP violating transitions in $^{12}$C using Borexino's low-background, large-mass detector data.

Findings

Established new lower bounds on PEP violation lifetimes in $^{12}$C.

Set upper limits on relative strengths of non-Paulian transitions.

Achieved the most stringent constraints to date on nucleon PEP violations.

Abstract

The Pauli exclusion principle (PEP) has been tested for nucleons ($n,p$) in $^{12}C$ with the Borexino detector.The approach consists of a search for $\gamma$, $n$, $p$ and $\beta^\pm$ emitted in a non-Paulian transition of 1$P_{3/2}$- shell nucleons to the filled 1$S_{1/2}$ shell in nuclei. Due to the extremely low background and the large mass (278 t) of the Borexino detector, the following most stringent up-to-date experimental bounds on PEP violating transitions of nucleons have been established: $\tau({^{12}\rm{C}}\to{^{12}\widetilde{\rm{C}}}+\gamma) \geq 5.0\cdot10^{31}$ y, $\tau({^{12}\rm{C}}\to{^{11}\widetilde{\rm{B}}}+ p) \geq 8.9\cdot10^{29}$ y, $\tau({^{12}\rm{C}}\to{^{11}\widetilde{\rm{C}}}+ n) \geq 3.4 \cdot 10^{30}$ y, $\tau({^{12}\rm{C}}\to{^{12}\widetilde{\rm{N}}}+ e^- + \widetilde{\nu_e}) \geq 3.1\cdot 10^{30}$ y and $\tau({^{12}\rm{C}}\to{^{12}\widetilde{\rm{B}}}+ e^+ + \nu_e) \geq 2.1 \cdot 10^{30}$ y, all at 90% C.L. The corresponding upper limits on the relative strengths for the searched non-Paulian electromagnetic, strong and weak transitions have been estimated: $\delta^2_{\gamma} \leq 2.2\cdot10^{-57}$, $\delta^2_{N} \leq 4.1\cdot10^{-60}$ and $\delta^2_{\beta} \leq 2.1\cdot10^{-35}$.