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

The Pauli exclusion principle (PEP) has been tested for nucleons (n, p) in C-12 and O-16 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 gamma, n, p and/or alpha' s emitted in a non-Paulian transition of 1P- shell nucleons to the filled 1S(1/2) shell in nuclei. Similarly, the Pauli-forbidden beta(+/-) 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: tau(C-12 --> (12)(C) over tilde + gamma) > 2.1 . 10(27) y, tau(C-12 --> (11)(B) over tilde + p) > 5.0 . 10(26) y, tau(C-12(O-16) --> 11 (C) over tilde((15)(O) over tilde) + n) > 3.7 . 10(26) y, tau(C-12 --> (8)(Be) over tilde+ alpha) > 6.1 . 10(23) y, tau(C-12 --> (12)(N) over tilde + e(-) + (nu) over tilde (e)) > 7.6 . 10(27) y and tau(C-12 --> (12)(B) over tilde + e(+) + nu(e)) > 7.7 . 10(27) y, all at 90% C. L.