On the Importance of Electron Diffusion in a Bulk-Matter Test of the Pauli Exclusion Principle

Abstract

The VIolation of Pauli (VIP) experiment (and its upgraded version, VIP-2) uses the Ramberg and Snow (RS) method (Phys. Lett. B 1990, 238, 438) to search for violations of the Pauli exclusion principle in the Gran Sasso underground laboratory. The RS method consists of feeding a copper conductor with a high direct current, so that the large number of newly-injected conduction electrons can interact with the copper atoms and possibly cascade electromagnetically to an already occupied atomic ground state if their wavefunction has the wrong symmetry with respect to the atomic electrons, emitting characteristic X-rays as they do so. In their original data analysis, RS considered a very simple path for each electron, which is sure to return a bound, albeit a very weak one, because it ignores the meandering random walks of the electrons as they move from the entrance to the exit of the copper sample. These complex walks bring the electrons close to many more atoms than in the RS calculation. Here, we consider the full description of these walks and show that this leads to a nontrivial and nonlinear X-ray emission rate. Finally, we obtain an improved

High Precision Test of the Pauli Exclusion Principle for Electrons

“…In Ref. [13] it is argued that scatterings are not actually related to the atoms themselves, but depend on impurities, lattice imperfections and on phonons. For this reason the mean time between close electron-atom encounters is instead evaluated in Ref.…”

“…For this reason the mean time between close electron-atom encounters is instead evaluated in Ref. [13], which is found to be 3.5·10 −17 s (instead of the much longer average scattering time 2.5 × 10 −14 ). Considered the traversal time of the copper target (which is estimated in [13] to amount to 10 s for the setup described in Section 2) an improved limit is obtained on the PEP violation probability: β 2 2 ≤ 2.6 · 10 −40 .…”

“…The analysis presented in Ref. [13] for the complex random walk which electron undergo in crossing the copper target material is mostly classical. We are presently working to extend the calculation to the quantum domain.…”

VIP2 in LNGS - Testing the Pauli Exclusion Principle for electrons with high sensitivity

“…magnitude (see fig.4). On the theoretical side studies are made to investigate the concept of new electrons provided by a current in the copper bulk material [20].…”

Search for a remnant violation of the Pauli exclusion principle in a Roman lead target

“…s see [10]), one finds about 1.21 × 10 21 (2.42 × 10 22 ) scatterings per year and, therefore, it would take at least 480 years (25 years) for a single electron to scatter off all the atoms in one mole of copper (lead). In [9] it is then assumed that also the free electrons already present in a conductor target can produce an anomalous X-ray signal from PEP violating transitions.…”