New experimental limits on violations of the Pauli exclusion principle obtained with the Borexino Counting Test Facility

Abstract

The Pauli exclusion principle (PEP) has been tested for nucleons ($n,p$) in ${}^{12}C$ and ${}^{16}O$ nuclei, using the results of background measurements with the prototype of the Borexino detector, the Counting Test Facility (CTF). The approach consisted of a search for ${\hat{I}}^3$, $n$, $p$ and/or $\hat{I}\pm$'s emitted in a non-Paulian transition of 1$P$- shell nucleons to the filled 1$S_{1/2}$ shell in nuclei. Similarly, the Pauli-forbidden $β^{\pm}$ decay processes were searched for. Due to the extremely low background and the large mass (4.2 tons) of the CTF detector, the following most stringent up-to-date experimental bounds on PEP violating transitions of nucleons have been established: $\ddot{I}„{(}^{12}C{\to }^{12}\tilde{C}+{\hat{I}}^3)>2.1\cdot 10^{27}$ y, $\ddot{I}„{(}^{12}C{\to }^{11}\tilde{B}+p)>5.0\cdot 10^{26}$ y, $\ddot{I}„{(}^{12}C{(}^{16}O){\to }^{11}\tilde{C}{(}^{15}\tilde{O})+n)>3.7\cdot 10^{26}$ y, $\ddot{I}„{(}^{12}C{\to }^8\widetilde{Be}+\hat{I}\pm )>6.1\cdot 10^{23}$ y, $\ddot{I}„{(}^{12}C{\to }^{12}\tilde{N}+e^{-}+\widetilde{\hat{I}{½}_e})>7.6\cdot 10^{27}$ y and $\ddot{I}„{(}^{12}C{\to }^{12}\tilde{B}+e^{+}+\hat{I}{½}_e)>7.7\cdot 10^{27}$ y, all at 90% C.L.

10 pages, 5 figures. Submitted to European Physical Journal C Spokesperson of the Borexino Collaboration: G.Bellini. Corresponding authors: A.Derbin, O.Smirnov