Colloquium: Laboratory constraint on the electric charge of the neutron and the neutrino

by Prof. Savely G. Karshenboim (Max-Planck-Institut für Quantenoptik, Garching, 85748, Germany)

Thursday 19 Mar 2026, 10:00 → 11:00 Europe/Vienna

Besprechungsraum 3A 1/2 (Marietta Blau Institute for Particle Physics, Dominikanerbastei 16 [PSK], 1010 Vienna)

The constraints on the value of the electric charge of the neutron and the neutrinos, as well as on the electric-charge proton-electron difference e_p+ e_e are revisited. The phenomenological constraints based on laboratory study of the electrical neutrality of would-be neutral subatomic, atomic, and molecular species under assumption of the conservation of the electric charge in β-decay, that relates the values of e_p + e_e, e_n, e_ν, are considered. Some of constraints published previously utilized an additional assumption e_ν = 0, which I do not.

A cosmological constraint at the level of 10⁻³⁵ e utilized by the Particle Data Group (PDG) in their Review of Particle Physics has been dismissed as a controversial one which makes the laboratorconstraints on e_ν dominant.

The phenomenological constraints from the available data of laboratory experiments are obtained as e_p+ e_e = (0.2 ± 2.6) × 10⁻²¹ e, e_n = (−0.4 ± 1.1) × 10⁻²¹ e, and e_ν = (0.6 ± 3.2) × 10⁻²¹ e. The ones on e_p+ e_e and e_n are at the same level as the related constraints of PDG, but somewhat different because of releasing the value of e_ν. The obtained e_ν constraint is several orders of magnitude weaker than the controversial cosmological result dominated in the PDG constraint, but several orders of magnitude stronger than the other individual e_ν constraints considered by PDG.

The consistency of the phenomenological constraints and the Standard model (SM) is also considered. The SM ignores the mass term of the neutrinos and cannot describe the neutrino oscillations, which makes it not a complete theory, but a part of it. It is demonstrated that the condition of the cancellation of the triangle anomalies within the complete theory does not disagree with the phenomenological constraints since different extensions of the SM may produce different additional contributions to the anomalies. A choice of the extension fixes the way how those contributions are organized. In particular, I consider a minimal extension of the SM, where leptons (ν,e) are treated the same ways as quarks, which sets e_p + e_e = 0 and allows for numerical strengthening the constraint on e_n and e_ν, which is e_n =−e_ν = (−0.4 ± 1.0) × 10⁻²¹ e.

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