| Autor: |
Chuan-Xin Cui, Jin-Yang Li, Hiroyuki Ishida, Mamiya Kawaguchi, Shinya Matsuzaki, Akio Tomiya |
| Jazyk: |
angličtina |
| Rok vydání: |
2024 |
| Předmět: |
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| Zdroj: |
Universe, Vol 10, Iss 2, p 68 (2024) |
| Druh dokumentu: |
article |
| ISSN: |
2218-1997 |
| DOI: |
10.3390/universe10020068 |
| Popis: |
We find that a big gap between indicators for the breaking strengths of the global chiral SU(2) and U(1) axial symmetries in the QCD of the standard model (SM) can be interpreted as a new fine-tuning problem. This may thus imply calling for a class beyond the SM, which turns out to favor having a new chiral symmetry, and the associated massless new quark is insensitive to the chiral SU(2) symmetry for the lightest up and down quarks so that the fine-tuning is relaxed. Our statistical estimate shows that QCD of the SM is by more than 300 standard deviations off the parameter space free from fine-tuning, and the significance will be greater as the lattice measurements on the QCD hadron observables become more accurate. We briefly address a dark QCD model with massless new quarks as one viable candidate. |
| Databáze: |
Directory of Open Access Journals |
| Externí odkaz: |
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