New limits on the Pauli forbidden transitions in 12C nuclei obtained with the complete Borexino dataset

The Pauli exclusion principle (PEP) was tested for nucleons in 12C nuclei using the Borexino dataset from 2007 to 2021. The approach consists of searching for γ - quanta, neutrons, protons, as well as electrons and positrons emitted in non-Paulian transitions of nucleons from the 1P3/2 shell to the filled 1S1/2 shell. Due to the uniquely low background level, the large mass, and long measurement time of the Borexino detector, the most stringent experimental constraints to date on the lifetime of the 12C nucleus with respect to PEP-forbidden transitions were obtained: τ(12C → 12C + γ ) ≥ 1.1 × 1032 y, τ(12C → 11B + p) ≥ 1.0 × 1031 y, τ(12C → 11C + n) ≥ 2.0 × 1031 y, τ(12C → 12N + e− + νe) ≥ 6.4 × 1030 y and τ(12C → 12B + e+ + νe) ≥ 6.6 × 1030 y (90% C.L.). The upper limits on the relative strengths for the non-Paulian electromagnetic, strong, and weak transitions have been obtained: δ2 γ ≤ 1.0×10−57, δ2 N ≤ 7.0×10−61 and δ2 β ≤ 9.6×10−36, all at 90% C.L.