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## Description

Title: | REAPPRAISAL of P,T-ODD PARAMETERS FROM THE IMPROVED CALCULATION OF ELECTRIC DIPOLE MOMENT OF 225Ra ATOM |

Author(s): | Prasannaa, Srinivasa |

Contributor(s): | Sahoo, Bijaya Kumar; Mitra, Ramanuj |

Subject(s): | Mini-symposium: Precision Spectroscopy for Fundamental Physics |

Abstract: | The parity and time-reversal symmetry violating electric dipole moments (EDMs) of diamagnetic atoms have the potential to probe physics beyond TeV scale. EDMs of atomic systems arise from the nuclear Schiff moment (NSM), $S$, and the tensor-pseudotensor (T-PT) electron-nucleus (e-N) interaction that is characterized by its coupling coefficient, $C_T$. A combination of high-precision experiment and relativistic many-body theory gives upper limits on these two quantities. Such limits aid in extracting bounds on EDMs of neutron, $d_n$, and proton, $d_p$, chromo-EDMs, and the quantum chromodynamics parameter, $|\bar{\theta}|$. Previous calculations on these quantities using relativistic coupled-cluster (RCC) theory differ by about 40 percent, as compared to the results obtained from other variants of relativistic many-body methods \footnote{Y. Singh and B. K. Sahoo, Phys. Rev. A \textbf{92}, 022502 (2015).}. In this work, we employ the recently developed relativistic normal coupled-cluster theory \footnote{B. K. Sahoo and B. P. Das Phys. Rev. Lett. \textbf{120}, 203001 (2018).}, which alleviates the deficiencies of RCC method, to obtain the EDM of $^{\mathrm{225}}$Ra, and combine it with the latest measurement to obtain limits on $S$ and $C_T$. Further, taking into account the enhancement to EDM due to octuple moment of $^{\mathrm{225}}$Ra, these limits are revised to $\langle \sigma_N \rangle |C_T| < 1.06 \times 10^{-7}$ and $S < 2.19 \times 10^{-10} |e| fm^3$, with $\langle \sigma_N \rangle$ being the nuclear Pauli spinor. The accuracy of our results is corroborated by the dipole polarizability, which is obtained as 257(8) $e a_0^3$. Our EDM results, in combination with measurement, are about 8\% and 28\% improvements over the limits that were reported using the relativistic coupled-cluster theory for the NSM and T-PT e-N coupling coefficient, respectively. Further combining with the nuclear calculations, we infer the following limits: $d_n < 1.15 \times 10^{-23} |e| cm$, $d_p < 1.1 \times 10^{-22} |e| cm$, $|\bar{\theta}| < 2.46 \times 10^{-10}$, and the combined up- and down- quark chromo-EDMs $|\tilde{d}_u - \tilde{d}_d| < 1.36 \times 10^{-26} |e|cm$. Though these bounds are not competitive at present with the current-best limits acquired from $^{199}$Hg atom, they can be bettered when the measurement of EDM in $^{225}$Ra improves by four orders. |

Issue Date: | 24-Jun-20 |

Publisher: | International Symposium on Molecular Spectroscopy |

Citation Info: | APS |

Genre: | CONFERENCE PAPER/PRESENTATION |

Type: | Text |

Language: | English |

URI: | http://hdl.handle.net/2142/107603 |

Date Available in IDEALS: | 2020-06-26 |