### Abstract

The neutron electric dipole moment (nEDM) is sensitive to new physics beyond the standard model and could prove to be a new source of CP violation. Several experiments are being planned worldwide for its high-precision measurement. The nEDM is measured as the ultracold neutron (UCN) spin precession in a storage bottle under homogeneous electric and magnetic fields. In nEDM measurement, the systematic uncertainties are due to the motion of the UCNs, the geometry of the measurement system, and inhomogeneous electric and magnetic fields. Therefore, it is essential to quantitatively understand these effects in order to reduce them. Geant4UCN is an ideal simulation framework because it can compute the UCN trajectory, evaluate the time evolution of the spin precession due to arbitrary electric and magnetic fields, and define the storage geometry flexibly. We checked how accurately Geant4UCN can calculate the spin precession. We found that because of rounding errors, it cannot simulate it accurately enough for nEDM experiments, assuming homogeneous electric and magnetic fields with strengths of 10 kV/cm and 1 μT, respectively, and 100 s of storage. In this paper, we report on its discrepancies and describe a solution.

Original language | English |
---|---|

Article number | 012031 |

Journal | Journal of Physics: Conference Series |

Volume | 528 |

Issue number | 1 |

DOIs | |

Publication status | Published - Jan 1 2014 |

Event | International Workshop on Neutron Optics and Detectors, NOP and D 2013 - Munich, Germany Duration: Jul 2 2013 → Jul 5 2013 |

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### All Science Journal Classification (ASJC) codes

- Physics and Astronomy(all)

### Cite this

*Journal of Physics: Conference Series*,

*528*(1), [012031]. https://doi.org/10.1088/1742-6596/528/1/012031

**Development of a simulation for measuring neutron electric dipole moment.** / Katayama, Ryo; Mishima, Kenji; Yamashita, Satoru; Sakurai, Dai; Kitaguchi, Masaaki; Yoshioka, Tamaki; Seki, Yoshichika.

Research output: Contribution to journal › Conference article

*Journal of Physics: Conference Series*, vol. 528, no. 1, 012031. https://doi.org/10.1088/1742-6596/528/1/012031

}

TY - JOUR

T1 - Development of a simulation for measuring neutron electric dipole moment

AU - Katayama, Ryo

AU - Mishima, Kenji

AU - Yamashita, Satoru

AU - Sakurai, Dai

AU - Kitaguchi, Masaaki

AU - Yoshioka, Tamaki

AU - Seki, Yoshichika

PY - 2014/1/1

Y1 - 2014/1/1

N2 - The neutron electric dipole moment (nEDM) is sensitive to new physics beyond the standard model and could prove to be a new source of CP violation. Several experiments are being planned worldwide for its high-precision measurement. The nEDM is measured as the ultracold neutron (UCN) spin precession in a storage bottle under homogeneous electric and magnetic fields. In nEDM measurement, the systematic uncertainties are due to the motion of the UCNs, the geometry of the measurement system, and inhomogeneous electric and magnetic fields. Therefore, it is essential to quantitatively understand these effects in order to reduce them. Geant4UCN is an ideal simulation framework because it can compute the UCN trajectory, evaluate the time evolution of the spin precession due to arbitrary electric and magnetic fields, and define the storage geometry flexibly. We checked how accurately Geant4UCN can calculate the spin precession. We found that because of rounding errors, it cannot simulate it accurately enough for nEDM experiments, assuming homogeneous electric and magnetic fields with strengths of 10 kV/cm and 1 μT, respectively, and 100 s of storage. In this paper, we report on its discrepancies and describe a solution.

AB - The neutron electric dipole moment (nEDM) is sensitive to new physics beyond the standard model and could prove to be a new source of CP violation. Several experiments are being planned worldwide for its high-precision measurement. The nEDM is measured as the ultracold neutron (UCN) spin precession in a storage bottle under homogeneous electric and magnetic fields. In nEDM measurement, the systematic uncertainties are due to the motion of the UCNs, the geometry of the measurement system, and inhomogeneous electric and magnetic fields. Therefore, it is essential to quantitatively understand these effects in order to reduce them. Geant4UCN is an ideal simulation framework because it can compute the UCN trajectory, evaluate the time evolution of the spin precession due to arbitrary electric and magnetic fields, and define the storage geometry flexibly. We checked how accurately Geant4UCN can calculate the spin precession. We found that because of rounding errors, it cannot simulate it accurately enough for nEDM experiments, assuming homogeneous electric and magnetic fields with strengths of 10 kV/cm and 1 μT, respectively, and 100 s of storage. In this paper, we report on its discrepancies and describe a solution.

UR - http://www.scopus.com/inward/record.url?scp=84906219481&partnerID=8YFLogxK

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U2 - 10.1088/1742-6596/528/1/012031

DO - 10.1088/1742-6596/528/1/012031

M3 - Conference article

AN - SCOPUS:84906219481

VL - 528

JO - Journal of Physics: Conference Series

JF - Journal of Physics: Conference Series

SN - 1742-6588

IS - 1

M1 - 012031

ER -