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

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: $\tau ({}^{12}\mathrm{C}\to {}^{12}\tilde{\mathrm{C}}+\gamma )\ge 5.0\cdot 10^{31}$ y, $\tau ({}^{12}\mathrm{C}\to {}^{11}\tilde{\mathrm{B}}+p)\ge 8.9\cdot 10^{29}$ y, $\tau ({}^{12}\mathrm{C}\to {}^{11}\tilde{\mathrm{C}}+n)\ge 3.4\cdot 10^{30}$ y, $\tau ({}^{12}\mathrm{C}\to {}^{12}\tilde{\mathrm{N}}+e^{-}+\widetilde{{\nu }_e})\ge 3.1\cdot 10^{30}$ y and $\tau ({}^{12}\mathrm{C}\to {}^{12}\tilde{\mathrm{B}}+e^{+}+{\nu }_e)\ge 2.1\cdot 10^{30}$ 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: ${\delta }_{\gamma }^2\le 2.2\cdot 10^{-57}$, ${\delta }_N^2\le 4.1\cdot 10^{-60}$ and ${\delta }_{\beta }^2\le 2.1\cdot 10^{-35}$.

9 pages, 6 figures