Restriction on the neutron-antineutron oscillations from the SNO data on the deuteron stability

We calculate the lifetime of the deuteron with dimension-nine quark operators that violate baryon number by two units. We construct an effective field theory for |∆B| = 2 interactions that give rise to neutron-antineutron (n-n) oscillations and dinucleon decay within a consistent power counting. We calculate the ratio of the deuteron lifetime to the square of the n-n oscillation time up to next-to-leading order. Our result, which is analytical and has a quantified uncertainty, is smaller by a factor ≃ 2.5 than earlier estimates based on nuclear models, which impacts the indirect bound on the n-n oscillation time and future experiments. We discuss how combined measurements of n-n oscillations and deuteron decay can help to identify the sources of baryon-number violation.a Corresponding author, f.oosterhof@rug.nl At the classical level the standard model (SM) has two accidental global U(1) symmetries associated with baryon-number (B) and lepton-number (L) conservation [1][2][3]. At the quantum level only B − L is conserved, while B + L is anomalous. Since it can be expected that all global symmetries are only approximate, it is plausible that beyond-the-SM (BSM) physics violates B, L, and B − L separately. For instance, extending the SM with the only gauge-invariant dimension-five operator leads to violation of L by two units [1][2][3]. Additional B-and L-violating operators appear at the dimension-six level, while the first gauge-invariant operators that violate B by two units (|∆B| = 2) appear at dimension nine [4].The best limits on B-violating interactions come from the observed stability of the proton. The limit on its lifetime translates into a scale Λ |∆B|=1 > ∼ 10 13 TeV for grand unified theories [5]. Such energies are out of reach of colliders. However, models exist wherein B is only violated by two units and the proton is stable [6][7][8]. These interactions lead to the oscillation of neutral baryons into antibaryons, in analogy to strangeness-changing SM interactions that lead to kaon-antikaon oscillations. In particular, a neutron in a beam can oscillate into an antineutron [9] that annihilates with a nucleon in a target, producing several pions with a few hundred MeV of energy [10]. An ILL experiment sets a lower limit on the neutronantineutron (n-n) oscillation time of τ nn > 0.86 × 10 8 s ≃ 2.7 yr (90% C.L.) [11], which converts to a BSM scale Λ |∆B|=2 > ∼ 10 2 TeV, within reach of future colliders. An experiment at the European Spallation Source can improve τ nn by two orders of magnitude [12], probing regions of parameter space relevant for the observed baryon asymmetry of the Universe [13].Apart from "in-vacuum" n-n oscillations, |∆B| = 2 interactions also induce the decay of otherwise stable nuclei. A bound neutron can oscillate inside the nucleus into an antineutron, which then annihilates with another nucleon. Since a neutron and an antineutron have very different potential energies, the typical nuclear lifetime is far greater than τ nn [4]. Alternatively, two nucleons can annihilate directly....

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“…[45,46] also reduce to our LO for a zero-range potential. (Reference [47] disagrees from these results by a factor of 2. )…”

Section: Operatormentioning

confidence: 83%

Baryon-Number Violation by Two Units and the Deuteron Lifetime

et al. 2019

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“…To consider this issue further we turn to the Qweak experiment at JLab [57], which uses a liquid hydrogen target and an electron beam with energy E = 1. 16 GeV and a beam current of 180 µA, yielding a beam power in this latter case of 0.209 MW. Thus for the estimate in our case, we suppose that we can lower the beam energy to 20 MeV, but keep the same beam current, so that the beam power will be within the range of the Qweak experiment and a liquid deuterium target can be used.…”

Section: Numerical Estimates and Experimental Prospectsmentioning

confidence: 97%

“…A next-generation experiment is also under development [10,11]. Independently, searches for neutron-antineutron oscillations in nuclei have been conducted, with the most stringent lower limit on the bound neutron lifetime being 1.9 × 10 32 years at 90% CL for neutrons in 16 O [12]. Employing a probabilistic computation of the nuclear suppression factor [13,14], with realistic nuclear optical potentials [14], yields an equivalent free neutron lifetime of 2.7 × 10 8 s at 90% CL [12].…”

Section: Introductionmentioning

confidence: 99%

“…Employing a probabilistic computation of the nuclear suppression factor [13,14], with realistic nuclear optical potentials [14], yields an equivalent free neutron lifetime of 2.7 × 10 8 s at 90% CL [12]. A recent study of the bound neutron lifetime in deuterium [15] also employs a probabilistic framework [16] to determine that the equivalent free neutron lifetime is no less than 1.23 × 10 8 s at 90% CL. We note that the ability of the free neutron experiment to observe a non-zero effect at its claimed sensitivity has been recently called into question [17], due to the use of a probabilistic, rather than a quantum kinetic, framework for its analysis.…”

Section: Introductionmentioning

confidence: 99%

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Phenomenology of neutron-antineutron conversion

Gardner¹,

Yan²

2018

Phys. Rev. D

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We consider the possibility of neutron-antineutron (n −n) conversion, in which the change of a neutron into an antineutron is mediated by an external source, as can occur in a scattering process. We develop the connections between n −n conversion and n −n oscillation, in which a neutron spontaneously transforms into an antineutron, noting that if n −n oscillation occurs in a theory with baryon number minus lepton number (B-L) violation, then n −n conversion can occur also. We show how an experimental limit on n −n conversion could connect concretely to a limit on n −n oscillation, and vice versa, using effective field theory techniques and baryon matrix elements computed in the MIT bag model.

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“…A new evaluation of the suppression factor in the deuteron was made by Kopeliovich and Potashnikova and includes the spin dependence of thenp annihilation amplitudes and a reevaluation of the zero-range approximation of the deuteron wave function [22], Of the two specific cases relevant to this analysis, n-n oscillations in 16 O and 2 H, we have chosen to study only the latter due to SNO's low sensitivity to O Fermi momentum (∼225 MeV) transferred to the daughter particles results in tracks that are closer in direction to each other than if the interaction had occurred at rest; this in turn complicates the reconstruction of the daughter particle's track.…”

Section: O Ofmentioning

confidence: 99%

Search for neutron-antineutron oscillations at the Sudbury Neutrino Observatory

Aharmim¹,

Ahmed²,

Anthony³

et al. 2017

Phys. Rev. D

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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.

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Restriction on the neutron-antineutron oscillations from the SNO data on the deuteron stability

Cited by 6 publications

References 24 publications

Baryon-Number Violation by Two Units and the Deuteron Lifetime

Baryon-Number Violation by Two Units and the Deuteron Lifetime

Phenomenology of neutron-antineutron conversion

Search for neutron-antineutron oscillations at the Sudbury Neutrino Observatory

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