Global analysis of $ \mathcal{CP} $-violation in atoms, molecules and role of medium-heavy systems

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2024年8月14日

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Konstantin Gaul,
Robert Berger

摘要

Detection of parity $(P)$ $ \left(\mathcal{P}\right) $ and time-reversal $(T)$ $ \left(\mathcal{T}\right) $ symmetry-odd electric dipole moments (EDMs) within currently achievable resolution would evidence physics beyond the Standard Model of particle physics. Via the $(CPT)$ $ \left(\mathcal{CPT}\right) $ -theorem, which includes charge conjugation $(C)$ $ \left(\mathcal{C}\right) $ , such low-energy searches complement high-energy physics experiments that probe $(CP)$ $ \left(\mathcal{CP}\right) $ -violation up to the TeV scale. Heavy-elemental atoms and molecules are considered to be among the most promising candidates for a first direct detection of $P$ $ \mathcal{P} $ , $T$ $ \mathcal{T} $ -violation due to enhancement effects that increase steeply with increasing nuclear charge number Z. However, different $P$ $ \mathcal{P} $ , $T$ $ \mathcal{T} $ -odd sources on the subatomic level can contribute to molecular or atomic EDMs, which are target of measurements, and this complicates obtaining rigorous bounds on $P$ $ \mathcal{P} $ , $T$ $ \mathcal{T} $ -violation on a fundamental level. Consequently, several experiments of complementary sensitivity to these individual $P$ $ \mathcal{P} $ , $T$ $ \mathcal{T} $ -odd sources are required for this purpose. Herein, a simply-applicable qualitative model is developed for global analysis of the $P$ $ \mathcal{P} $ , $T$ $ \mathcal{T} $ -odd parameter space from an electronic-structure theory perspective. Rules of thumb are derived for the choice of atoms and molecules in terms of their angular momenta and nuclear charge number. Contrary to naive expectations from Z-scaling laws, it is demonstrated that medium-heavy molecules with Z ≤ 54 can be of great value to tighten global bounds on $P$ $ \mathcal{P} $ , $T$ $ \mathcal{T} $ -violating parameters, in particular, if the number of complementary experiments increases. The model is confirmed by explicit density functional theory calculations of all relevant $P$ $ \mathcal{P} $ , $T$ $ \mathcal{T} $ -odd electronic structure parameters in systems that were used in past experiments or are of current interest for future experiments, respectively: the atoms Xe, Cs, Yb, Hg, Tl, Ra, Fr and the molecules CaOH, SrOH, YO, CdH, BaF, YbF, YbOH, HfF⁺, WC, TlF, PbO, RaF, ThO, ThF⁺ and PaF³⁺.

Global analysis of \( \mathcal{CP} \)-violation in atoms, molecules and role of medium-heavy systems

摘要