Probing the QCD θ ¯ $$ \overline{\theta} $$ term with paramagnetic molecules
Abstract The experimental search for CP violation in paramagnetic atomic and molecular systems has made impressive progress in recent years. This has led to strong upper limits on the electron electric dipole moment. The same measurements can also be used to constrain hadronic sources of CP violatio...
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| Format: | Article |
| Language: | English |
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SpringerOpen
2025-07-01
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| Series: | Journal of High Energy Physics |
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| Online Access: | https://doi.org/10.1007/JHEP07(2025)232 |
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| author | Heleen Mulder Rob Timmermans Jordy de Vries |
| author_facet | Heleen Mulder Rob Timmermans Jordy de Vries |
| author_sort | Heleen Mulder |
| collection | DOAJ |
| description | Abstract The experimental search for CP violation in paramagnetic atomic and molecular systems has made impressive progress in recent years. This has led to strong upper limits on the electron electric dipole moment. The same measurements can also be used to constrain hadronic sources of CP violation through CP-violating interactions between the electrons and the nucleus. We employ heavy-baryon chiral perturbation theory to compute such CP-violating semileptonic electron-nucleus interactions arising from the QCD theta term. We sharpen earlier results by determining the relevant short-distance effects and by an explicit two-loop calculation of meson-photon diagrams. We derive a bound of θ ¯ $$ \left|\overline{\theta}\right| $$ < 1.5·10−8 at 90% confidence, based on HfF+ experiments at JILA. A further experimental improvement of one to two orders of magnitude would make paramagnetic molecular electric dipole moment experiments competitive with the neutron and diamagnetic atom program in constraining strong CP violation and higher-dimensional CP-odd quark-gluon operators. |
| format | Article |
| id | doaj-art-a90d792eb27f48ffbf6ca5d6191773e6 |
| institution | DOAJ |
| issn | 1029-8479 |
| language | English |
| publishDate | 2025-07-01 |
| publisher | SpringerOpen |
| record_format | Article |
| series | Journal of High Energy Physics |
| spelling | doaj-art-a90d792eb27f48ffbf6ca5d6191773e62025-08-20T03:04:08ZengSpringerOpenJournal of High Energy Physics1029-84792025-07-012025712310.1007/JHEP07(2025)232Probing the QCD θ ¯ $$ \overline{\theta} $$ term with paramagnetic moleculesHeleen Mulder0Rob Timmermans1Jordy de Vries2Nikhef, National Institute for Subatomic PhysicsNikhef, National Institute for Subatomic PhysicsNikhef, National Institute for Subatomic PhysicsAbstract The experimental search for CP violation in paramagnetic atomic and molecular systems has made impressive progress in recent years. This has led to strong upper limits on the electron electric dipole moment. The same measurements can also be used to constrain hadronic sources of CP violation through CP-violating interactions between the electrons and the nucleus. We employ heavy-baryon chiral perturbation theory to compute such CP-violating semileptonic electron-nucleus interactions arising from the QCD theta term. We sharpen earlier results by determining the relevant short-distance effects and by an explicit two-loop calculation of meson-photon diagrams. We derive a bound of θ ¯ $$ \left|\overline{\theta}\right| $$ < 1.5·10−8 at 90% confidence, based on HfF+ experiments at JILA. A further experimental improvement of one to two orders of magnitude would make paramagnetic molecular electric dipole moment experiments competitive with the neutron and diamagnetic atom program in constraining strong CP violation and higher-dimensional CP-odd quark-gluon operators.https://doi.org/10.1007/JHEP07(2025)232Chiral LagrangianCP ViolationEffective Field Theories of QCDElectric Dipole Moments |
| spellingShingle | Heleen Mulder Rob Timmermans Jordy de Vries Probing the QCD θ ¯ $$ \overline{\theta} $$ term with paramagnetic molecules Journal of High Energy Physics Chiral Lagrangian CP Violation Effective Field Theories of QCD Electric Dipole Moments |
| title | Probing the QCD θ ¯ $$ \overline{\theta} $$ term with paramagnetic molecules |
| title_full | Probing the QCD θ ¯ $$ \overline{\theta} $$ term with paramagnetic molecules |
| title_fullStr | Probing the QCD θ ¯ $$ \overline{\theta} $$ term with paramagnetic molecules |
| title_full_unstemmed | Probing the QCD θ ¯ $$ \overline{\theta} $$ term with paramagnetic molecules |
| title_short | Probing the QCD θ ¯ $$ \overline{\theta} $$ term with paramagnetic molecules |
| title_sort | probing the qcd θ ¯ overline theta term with paramagnetic molecules |
| topic | Chiral Lagrangian CP Violation Effective Field Theories of QCD Electric Dipole Moments |
| url | https://doi.org/10.1007/JHEP07(2025)232 |
| work_keys_str_mv | AT heleenmulder probingtheqcdthoverlinethetatermwithparamagneticmolecules AT robtimmermans probingtheqcdthoverlinethetatermwithparamagneticmolecules AT jordydevries probingtheqcdthoverlinethetatermwithparamagneticmolecules |