# Neutron-Antineutron Oscillations from Lattice QCD

## Abstract

Fundamental symmetry tests of baryon number violation in low-energy experiments can probe beyond the standard model (BSM) explanations of the matter-antimatter asymmetry of the Universe. Neutron-antineutron oscillations are predicted to be a signature of many baryogenesis mechanisms involving low-scale baryon number violation. This Letter presents first-principles calculations of neutron-antineutron matrix elements needed to accurately connect measurements of the neutron-antineutron oscillation rate to constraints on |ΔB| = 2 baryon number violation in BSM theories. Several important systematic uncertainties are controlled by using a state-of-the-art lattice gauge field ensemble with physical quark masses and approximate chiral symmetry, performing nonperturbative renormalization with perturbative matching to the modified minimal subtraction scheme, and studying excited state effects in two-state fits. Phenomenological implications are highlighted by comparing expected bounds from proposed neutron-antineutron oscillation experiments to predictions of a specific model of postsphaleron baryogenesis. Quantum chromodynamics is found to predict at least an order of magnitude more events in neutron-antineutron oscillation experiments than previous estimates based on the “MIT bag model” for fixed BSM parameters. Lattice artifacts and other systematic uncertainties that are not controlled in this pioneering calculation are not expected to significantly change this conclusion.

- Authors:

- Publication Date:

- Research Org.:
- Brookhaven National Lab. (BNL), Upton, NY (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

- Sponsoring Org.:
- USDOE Office of Science (SC), Nuclear Physics (NP); USDOE National Nuclear Security Administration (NNSA)

- OSTI Identifier:
- 1508198

- Alternate Identifier(s):
- OSTI ID: 1511574; OSTI ID: 1860792

- Report Number(s):
- BNL-211593-2019-JAAM; LLNL-JRNL-757017

Journal ID: ISSN 0031-9007; PRLTAO; 162001

- Grant/Contract Number:
- AC52-07NA27344; FG02-00ER41132; SC0012704; SC0011090; AC02-06CH11357

- Resource Type:
- Published Article

- Journal Name:
- Physical Review Letters

- Additional Journal Information:
- Journal Name: Physical Review Letters Journal Volume: 122 Journal Issue: 16; Journal ID: ISSN 0031-9007

- Publisher:
- American Physical Society

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

### Citation Formats

```
Rinaldi, Enrico, Syritsyn, Sergey, Wagman, Michael L., Buchoff, Michael I., Schroeder, Chris, and Wasem, Joseph. Neutron-Antineutron Oscillations from Lattice QCD. United States: N. p., 2019.
Web. doi:10.1103/PhysRevLett.122.162001.
```

```
Rinaldi, Enrico, Syritsyn, Sergey, Wagman, Michael L., Buchoff, Michael I., Schroeder, Chris, & Wasem, Joseph. Neutron-Antineutron Oscillations from Lattice QCD. United States. https://doi.org/10.1103/PhysRevLett.122.162001
```

```
Rinaldi, Enrico, Syritsyn, Sergey, Wagman, Michael L., Buchoff, Michael I., Schroeder, Chris, and Wasem, Joseph. Mon .
"Neutron-Antineutron Oscillations from Lattice QCD". United States. https://doi.org/10.1103/PhysRevLett.122.162001.
```

```
@article{osti_1508198,
```

title = {Neutron-Antineutron Oscillations from Lattice QCD},

author = {Rinaldi, Enrico and Syritsyn, Sergey and Wagman, Michael L. and Buchoff, Michael I. and Schroeder, Chris and Wasem, Joseph},

abstractNote = {Fundamental symmetry tests of baryon number violation in low-energy experiments can probe beyond the standard model (BSM) explanations of the matter-antimatter asymmetry of the Universe. Neutron-antineutron oscillations are predicted to be a signature of many baryogenesis mechanisms involving low-scale baryon number violation. This Letter presents first-principles calculations of neutron-antineutron matrix elements needed to accurately connect measurements of the neutron-antineutron oscillation rate to constraints on |ΔB| = 2 baryon number violation in BSM theories. Several important systematic uncertainties are controlled by using a state-of-the-art lattice gauge field ensemble with physical quark masses and approximate chiral symmetry, performing nonperturbative renormalization with perturbative matching to the modified minimal subtraction scheme, and studying excited state effects in two-state fits. Phenomenological implications are highlighted by comparing expected bounds from proposed neutron-antineutron oscillation experiments to predictions of a specific model of postsphaleron baryogenesis. Quantum chromodynamics is found to predict at least an order of magnitude more events in neutron-antineutron oscillation experiments than previous estimates based on the “MIT bag model” for fixed BSM parameters. Lattice artifacts and other systematic uncertainties that are not controlled in this pioneering calculation are not expected to significantly change this conclusion.},

doi = {10.1103/PhysRevLett.122.162001},

journal = {Physical Review Letters},

number = 16,

volume = 122,

place = {United States},

year = {2019},

month = {4}

}

https://doi.org/10.1103/PhysRevLett.122.162001

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#### Figures / Tables:

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Figures / Tables found in this record:

*Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.*