Elastic and transition form factors of light pseudoscalar mesons from QCD sum rules
| Autor: | Balakireva, Irina, Lucha, Wolfgang, Melikhov, Dmitri |
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| Rok vydání: | 2012 |
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| Zdroj: | Phys. Atom. Nucl. 76: 326-340, 2013 |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1134/S106377881302004X |
| Popis: | We revisit $F_\pi(Q^2)$ and $F_{P\gamma}(Q^2)$, $P=\pi,\eta,\eta'$, making use of the local-duality (LD) version of QCD sum rules. We give arguments, that the LD sum rule provides reliable predictions for these form factors at $Q^2 \ge 5-6$ GeV$^2$, the accuracy of the method increasing with $Q^2$ in this region. For the pion elastic form factor, the well-measured data at small $Q^2$ give a hint that the LD limit may be reached already at relatively low values of momentum transfers, $Q^2\approx 4-8$ GeV$^2$; we therefore conclude that large deviations from LD in the region $Q^2=20-50$ GeV$^2$ seem very unlikely. The data on the ($\eta,\eta')\to\gamma\gamma^*$ form factors meet the expectations from the LD model. However, the {\sc BaBar} results for the $\pi^0\to\gamma\gamma^*$ form factor imply a violation of LD growing with $Q^2$ even at $Q^2\approx 40$ GeV$^2$, at odds with the $\eta,\eta'$ case and with the general properties expected for the LD sum rule. Comment: 17 pages. arXiv admin note: substantial text overlap with arXiv:1103.3781 and arXiv:1110.6904 |
| Databáze: | arXiv |
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