Search for neutron-antineutron oscillations at the Sudbury Neutrino Observatory

Abstract

Tests on B − L symmetry breaking models are important probes to search for new physics. One proposed model with ΔðB − LÞ ¼ 2 involves the oscillations of a neutron to an antineutron. In this paper, a new limit on this process is derived for the data acquired from all three operational phases of the Sudbury Neutrino Observatory experiment. The search concentrated on oscillations occurring within the deuteron, and 23 events were observed against a background expectation of 30.5 events. These translated to a lower limit on the nuclear lifetime of 1.48 × 10 31 yr at 90% C.L. when no restriction was placed on the signal likelihood space (unbounded). Alternatively, a lower limit on the nuclear lifetime was found to be 1.18 × 10 31 yr at 90% C.L. when the signal was forced into a positive likelihood space (bounded). Values for the free oscillation time derived from various models are also provided in this article. This is the first search for neutron-antineutron oscillation with the deuteron as a target.

Baryon-number-violating nucleon and dinucleon decays in a model with large extra dimensions

“…Hence, for the fermions f = u, d and also f = ℓ = e, , µ, τ (neglecting off-diagonal elements in the Yukawa matrices), we have 16) or equivalently, the following constraint on the separation distance η fL − η fR :…”

“…Using the value R ≃ 0.52 × 10 23 sec −1 for the 16 O nuclei in water (see, e.g., [29] and references therein), the SK experiment gives the lower limit…”

Connection between νn→ν¯n¯ reactions and n−Hao1 2020Phys. Rev. D3010View full textAdd to dashboardCite

“…The constraints on nucleon instability can be determined through the measurements of two decay modes, such as n-n oscillations [25][26][27][28][29][30] and the dineutron decay: nn →νν [46]. Such decay modes violate B and (B + L) but the dineutron decay preserves (B − L).…”

“…Here p1 and p2 are the four-momenta of the incoming neutrino and neutron respectively, and p4 and p3 are the four-momenta of the outgoing antineutrino and antineutron respectively. arXiv:1912.04188v2 [hep-ph] 7 Feb 2020 [29], and Sudbury Neutrino Observatory (SNO) [30]. In field-free vacuum, the present best lower limit on the n-n oscillation time is reported by the ILL experiment [31].…”

“…At the quark level, B, (B + L), and (B − L) violations can only be described by high dimensional operators associated with some large mass scales and thus the effect is greatly suppressed and usually considered to be undetectable at low energies [32]. The lower limits on n-n oscillation times for neutrons in matter are derived from the stability of nuclei [25][26][27][28][29][30]. However, the instability of nuclei induced by external low-energy solar neutrinos has not been excluded because of the detector thresholds.…”