Development of a simulation for measuring neutron electric dipole moment

Ryo Katayama, Kenji Mishima, Satoru Yamashita, Dai Sakurai, Masaaki Kitaguchi, Tamaki Yoshioka, Yoshichika Seki

Research output: Contribution to journalConference articlepeer-review

1 Citation (Scopus)


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 languageEnglish
Article number012031
JournalJournal of Physics: Conference Series
Issue number1
Publication statusPublished - 2014
EventInternational Workshop on Neutron Optics and Detectors, NOP and D 2013 - Munich, Germany
Duration: Jul 2 2013Jul 5 2013

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)


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