Novel loop-diagrammatic approach to QCD θ parameter and application to the left-right model
Abstract When the QCD axion is absent in full theory, the strong CP problem has to be explained by an additional mechanism, e.g., the left-right symmetry. Even though tree-level QCD θ ¯ $$ \overline{\theta} $$ parameter is restricted by the mechanism, radiative corrections to θ ¯ $$ \overline{\theta...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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SpringerOpen
2023-03-01
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| Series: | Journal of High Energy Physics |
| Subjects: | |
| Online Access: | https://doi.org/10.1007/JHEP03(2023)150 |
| _version_ | 1797795931939143680 |
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| author | Junji Hisano Teppei Kitahara Naohiro Osamura Atsuyuki Yamada |
| author_facet | Junji Hisano Teppei Kitahara Naohiro Osamura Atsuyuki Yamada |
| author_sort | Junji Hisano |
| collection | DOAJ |
| description | Abstract When the QCD axion is absent in full theory, the strong CP problem has to be explained by an additional mechanism, e.g., the left-right symmetry. Even though tree-level QCD θ ¯ $$ \overline{\theta} $$ parameter is restricted by the mechanism, radiative corrections to θ ¯ $$ \overline{\theta} $$ are mostly generated, which leads to a dangerous neutron electric dipole moment (EDM). The ordinary method for calculating the radiative θ ¯ $$ \overline{\theta} $$ utilizes an equation θ ¯ = − arg det m q loop $$ \overline{\theta}=-\arg\ \det {m}_q^{\textrm{loop}} $$ based on the chiral rotations of complex quark masses. In this paper, we point out that when full theory includes extra heavy quarks, the ordinary method is unsettled for the extra quark contributions and does not contain its full radiative corrections. We formulate a novel method to calculate the radiative corrections to θ ¯ $$ \overline{\theta} $$ through a direct loop-diagrammatic approach, which should be more robust than the ordinary one. As an application, we investigate the radiative θ ¯ $$ \overline{\theta} $$ in the minimal left-right symmetric model. We first confirm a seminal result that two-loop level radiative θ ¯ $$ \overline{\theta} $$ completely vanishes (corresponding to one-loop corrections to the quark mass matrices). Furthermore, we estimate the size of a non-vanishing radiative θ ¯ $$ \overline{\theta} $$ at three-loop level. It is found that the resultant induced neutron EDM is comparable to the current experimental bound, and the expected size is restricted by the perturbative unitarity bound in the minimal left-right model. |
| first_indexed | 2024-03-13T03:25:29Z |
| format | Article |
| id | doaj.art-aa9bcf6ea4834f5fbea8ed92340e7d3f |
| institution | Directory Open Access Journal |
| issn | 1029-8479 |
| language | English |
| last_indexed | 2024-03-13T03:25:29Z |
| publishDate | 2023-03-01 |
| publisher | SpringerOpen |
| record_format | Article |
| series | Journal of High Energy Physics |
| spelling | doaj.art-aa9bcf6ea4834f5fbea8ed92340e7d3f2023-06-25T11:05:20ZengSpringerOpenJournal of High Energy Physics1029-84792023-03-012023313210.1007/JHEP03(2023)150Novel loop-diagrammatic approach to QCD θ parameter and application to the left-right modelJunji Hisano0Teppei Kitahara1Naohiro Osamura2Atsuyuki Yamada3Department of Physics, Nagoya UniversityKobayashi-Maskawa Institute for the Origin of Particles and the Universe, Nagoya UniversityDepartment of Physics, Nagoya UniversityDepartment of Physics, Nagoya UniversityAbstract When the QCD axion is absent in full theory, the strong CP problem has to be explained by an additional mechanism, e.g., the left-right symmetry. Even though tree-level QCD θ ¯ $$ \overline{\theta} $$ parameter is restricted by the mechanism, radiative corrections to θ ¯ $$ \overline{\theta} $$ are mostly generated, which leads to a dangerous neutron electric dipole moment (EDM). The ordinary method for calculating the radiative θ ¯ $$ \overline{\theta} $$ utilizes an equation θ ¯ = − arg det m q loop $$ \overline{\theta}=-\arg\ \det {m}_q^{\textrm{loop}} $$ based on the chiral rotations of complex quark masses. In this paper, we point out that when full theory includes extra heavy quarks, the ordinary method is unsettled for the extra quark contributions and does not contain its full radiative corrections. We formulate a novel method to calculate the radiative corrections to θ ¯ $$ \overline{\theta} $$ through a direct loop-diagrammatic approach, which should be more robust than the ordinary one. As an application, we investigate the radiative θ ¯ $$ \overline{\theta} $$ in the minimal left-right symmetric model. We first confirm a seminal result that two-loop level radiative θ ¯ $$ \overline{\theta} $$ completely vanishes (corresponding to one-loop corrections to the quark mass matrices). Furthermore, we estimate the size of a non-vanishing radiative θ ¯ $$ \overline{\theta} $$ at three-loop level. It is found that the resultant induced neutron EDM is comparable to the current experimental bound, and the expected size is restricted by the perturbative unitarity bound in the minimal left-right model.https://doi.org/10.1007/JHEP03(2023)150CP ViolationElectric Dipole MomentsLeft-Right Models |
| spellingShingle | Junji Hisano Teppei Kitahara Naohiro Osamura Atsuyuki Yamada Novel loop-diagrammatic approach to QCD θ parameter and application to the left-right model Journal of High Energy Physics CP Violation Electric Dipole Moments Left-Right Models |
| title | Novel loop-diagrammatic approach to QCD θ parameter and application to the left-right model |
| title_full | Novel loop-diagrammatic approach to QCD θ parameter and application to the left-right model |
| title_fullStr | Novel loop-diagrammatic approach to QCD θ parameter and application to the left-right model |
| title_full_unstemmed | Novel loop-diagrammatic approach to QCD θ parameter and application to the left-right model |
| title_short | Novel loop-diagrammatic approach to QCD θ parameter and application to the left-right model |
| title_sort | novel loop diagrammatic approach to qcd θ parameter and application to the left right model |
| topic | CP Violation Electric Dipole Moments Left-Right Models |
| url | https://doi.org/10.1007/JHEP03(2023)150 |
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