Using parity-nonconserving spin-spin coupling to measure the Tl nuclear anapole moment in a TlF molecular beam

An experiment utilizing a TlF molecular beam is being developed by the CeNTREX collaboration to search for hadronic interactions that violate both time-reversal (T) and parity (P) invariance. Here, we propose to use the same beam to look for a T-invariance conserving but P-nonconserving (PNC) effect induced by the anapole moment of the Tl nucleus, via a vector coupling of the two nuclear spins in TlF. To measure the nuclear anapole moment, the dc electric and magnetic fields in CeNTREX are replaced by rf fields resonant with a nuclear spin-flip transition. We adapt the relativistic coupled-cluster method in combination with relativistic density functional theory for the calculation of the molecular PNC spin-spin vector coupling constant that links the experimental signal with the anapole moment. The value of the P-conserving spin-spin coupling constant calculated within the same approach is found to be in good agreement with available experimental data.

Automated summary

CeNTREX is developing an experiment using a TlF molecular beam to search for hadronic interactions that violate both time-reversal (T) and parity (P) invariance. They also propose to use the same beam to look for a T-invariance conserving but P-nonconserving (PNC) effect induced by the anapole moment of the Tl nucleus. To measure the nuclear anapole moment, they replace the dc electric and magnetic fields in CeNTREX with rf fields resonant with a nuclear spin-flip transition. They use the relativistic coupled-cluster method in combination with relativistic density functional theory to calculate the molecular PNC spin-spin vector coupling constant that links the experimental signal with the anapole moment. The calculated value of the P-conserving spin-spin coupling constant is in good agreement with available experimental data.