Emerging understanding of the \Delta I = 1/2 Rule from Lattice QCD
| Autor: | Boyle, P. A., Christ, N. H., Garron, N., Goode, E. J., Janowski, T., Lehner, C., Liu, Q., Lytle, A. T., Sachrajda, C. T., Soni, A., Zhang, D. |
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| Rok vydání: | 2012 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1103/PhysRevLett.110.152001 |
| Popis: | There has been much speculation as to the origin of the \Delta I = 1/2 rule (Re A_0/Re A_2 \simeq 22.5). We find that the two dominant contributions to the \Delta I=3/2, K \to \pi \pi{} correlation functions have opposite signs leading to a significant cancellation. This partial cancellation occurs in our computation of Re A_2 with physical quark masses and kinematics (where we reproduce the experimental value of A_2) and also for heavier pions at threshold. For Re A_0, although we do not have results at physical kinematics, we do have results for pions at zero-momentum with m_\pi{} \simeq 420 MeV (Re A_0/Re A_2=9.1(2.1)) and m_\pi{} \simeq 330 MeV (Re A_0/Re A_2=12.0(1.7)). The contributions which partially cancel in Re A_2 are also the largest ones in Re A_0, but now they have the same sign and so enhance this amplitude. The emerging explanation of the \Delta I=1/2 rule is a combination of the perturbative running to scales of O(2 GeV), a relative suppression of Re A_2 through the cancellation of the two dominant contributions and the corresponding enhancement of Re A_0. QCD and EWP penguin operators make only very small contributions at such scales. Comment: 5 pages, 4 figures. v2 minor revisions to coincide w/ published version |
| Databáze: | arXiv |
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