Leptoquarks meet ε ′/ε and rare Kaon processes
Abstract We analyse for the first time the CP violating ratio ε ′/ε in K → ππ decays in leptoquark (LQ) models. Assuming a mass gap to the electroweak (EW) scale, the main mechanism for LQs to contribute to ε ′ /ε is EW gauge-mixing of semi-leptonic into non-leptonic operators, which we treat in the...
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| Format: | Article |
| Language: | English |
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SpringerOpen
2018-02-01
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| Series: | Journal of High Energy Physics |
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| Online Access: | http://link.springer.com/article/10.1007/JHEP02(2018)101 |
| _version_ | 1818520653119094784 |
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| author | Christoph Bobeth Andrzej J. Buras |
| author_facet | Christoph Bobeth Andrzej J. Buras |
| author_sort | Christoph Bobeth |
| collection | DOAJ |
| description | Abstract We analyse for the first time the CP violating ratio ε ′/ε in K → ππ decays in leptoquark (LQ) models. Assuming a mass gap to the electroweak (EW) scale, the main mechanism for LQs to contribute to ε ′ /ε is EW gauge-mixing of semi-leptonic into non-leptonic operators, which we treat in the Standard Model effective theory (SMEFT). We perform also the one-loop decoupling for scalar LQs, finding that in all models with both left-handed and right-handed LQ couplings box-diagrams generate numerically strongly enhanced EW-penguin operators Q 8,8′ already at the LQ scale. We then investigate correlations of ε ′ /ε with rare Kaon processes ( KL→π0νν¯ $$ {K}_L\to {\pi}^0\nu \overline{\nu} $$, K+→π+νν¯ $$ {K}^{+}\to {\pi}^{+}\nu \overline{\nu} $$, KL→π0ℓℓ¯ $$ {K}_L\to {\pi}^0\ell \overline{\ell} $$, KS→μμ¯ $$ {K}_S\to \mu \overline{\mu} $$, ΔM K and ε K ) and find that even imposing only a moderate enhancement of (ε ′ /ε)NP = 5 × 10−4 to explain the current anomaly hinted by the Dual QCD approach and RBC-UKQCD lattice QCD calculations leads to conflicts with experimental upper bounds on rare Kaon processes. They exclude all LQ models with only a single coupling as an explanation of the ε ′ /ε anomaly and put strong-to-serious constraints on parameter spaces of the remaining models. Future results on K+→π+νν¯ $$ {K}^{+}\to {\pi}^{+}\nu \overline{\nu} $$ from the NA62 collaboration, KL→π0νν¯ $$ {K}_L\to {\pi}^0\nu \overline{\nu} $$ from the KOTO experiment and KS→μμ¯ $$ {K}_S\to \mu \overline{\mu} $$ from LHCb will even stronger exhibit the difficulty of LQ models in explaining the measured ε ′ /ε, in case the ε ′ /ε anomaly will be confirmed by improved lattice QCD calculations. Hopefully also improved measurements of KL→π0ℓℓ¯ $$ {K}_L\to {\pi}^0\ell \overline{\ell} $$ decays will one day help in this context. |
| first_indexed | 2024-12-11T01:40:19Z |
| format | Article |
| id | doaj.art-350d29029c9b4732b538bce94e84f606 |
| institution | Directory Open Access Journal |
| issn | 1029-8479 |
| language | English |
| last_indexed | 2024-12-11T01:40:19Z |
| publishDate | 2018-02-01 |
| publisher | SpringerOpen |
| record_format | Article |
| series | Journal of High Energy Physics |
| spelling | doaj.art-350d29029c9b4732b538bce94e84f6062022-12-22T01:25:04ZengSpringerOpenJournal of High Energy Physics1029-84792018-02-012018215210.1007/JHEP02(2018)101Leptoquarks meet ε ′/ε and rare Kaon processesChristoph Bobeth0Andrzej J. Buras1TUM Institute for Advanced StudyTUM Institute for Advanced StudyAbstract We analyse for the first time the CP violating ratio ε ′/ε in K → ππ decays in leptoquark (LQ) models. Assuming a mass gap to the electroweak (EW) scale, the main mechanism for LQs to contribute to ε ′ /ε is EW gauge-mixing of semi-leptonic into non-leptonic operators, which we treat in the Standard Model effective theory (SMEFT). We perform also the one-loop decoupling for scalar LQs, finding that in all models with both left-handed and right-handed LQ couplings box-diagrams generate numerically strongly enhanced EW-penguin operators Q 8,8′ already at the LQ scale. We then investigate correlations of ε ′ /ε with rare Kaon processes ( KL→π0νν¯ $$ {K}_L\to {\pi}^0\nu \overline{\nu} $$, K+→π+νν¯ $$ {K}^{+}\to {\pi}^{+}\nu \overline{\nu} $$, KL→π0ℓℓ¯ $$ {K}_L\to {\pi}^0\ell \overline{\ell} $$, KS→μμ¯ $$ {K}_S\to \mu \overline{\mu} $$, ΔM K and ε K ) and find that even imposing only a moderate enhancement of (ε ′ /ε)NP = 5 × 10−4 to explain the current anomaly hinted by the Dual QCD approach and RBC-UKQCD lattice QCD calculations leads to conflicts with experimental upper bounds on rare Kaon processes. They exclude all LQ models with only a single coupling as an explanation of the ε ′ /ε anomaly and put strong-to-serious constraints on parameter spaces of the remaining models. Future results on K+→π+νν¯ $$ {K}^{+}\to {\pi}^{+}\nu \overline{\nu} $$ from the NA62 collaboration, KL→π0νν¯ $$ {K}_L\to {\pi}^0\nu \overline{\nu} $$ from the KOTO experiment and KS→μμ¯ $$ {K}_S\to \mu \overline{\mu} $$ from LHCb will even stronger exhibit the difficulty of LQ models in explaining the measured ε ′ /ε, in case the ε ′ /ε anomaly will be confirmed by improved lattice QCD calculations. Hopefully also improved measurements of KL→π0ℓℓ¯ $$ {K}_L\to {\pi}^0\ell \overline{\ell} $$ decays will one day help in this context.http://link.springer.com/article/10.1007/JHEP02(2018)101Beyond Standard ModelCP violationEffective Field TheoriesKaon Physics |
| spellingShingle | Christoph Bobeth Andrzej J. Buras Leptoquarks meet ε ′/ε and rare Kaon processes Journal of High Energy Physics Beyond Standard Model CP violation Effective Field Theories Kaon Physics |
| title | Leptoquarks meet ε ′/ε and rare Kaon processes |
| title_full | Leptoquarks meet ε ′/ε and rare Kaon processes |
| title_fullStr | Leptoquarks meet ε ′/ε and rare Kaon processes |
| title_full_unstemmed | Leptoquarks meet ε ′/ε and rare Kaon processes |
| title_short | Leptoquarks meet ε ′/ε and rare Kaon processes |
| title_sort | leptoquarks meet ε ε and rare kaon processes |
| topic | Beyond Standard Model CP violation Effective Field Theories Kaon Physics |
| url | http://link.springer.com/article/10.1007/JHEP02(2018)101 |
| work_keys_str_mv | AT christophbobeth leptoquarksmeeteeandrarekaonprocesses AT andrzejjburas leptoquarksmeeteeandrarekaonprocesses |