Second Gegenbauer moment of a ρ -meson distribution amplitude
| Autor: | Maxim V. Polyakov, Hyeon-Dong Son |
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| Rok vydání: | 2020 |
| Předmět: | |
| Zdroj: | Physical Review |
| ISSN: | 2470-0029 2470-0010 |
| Popis: | Using the soft pion theorem, crossing, and the dispersion relations for the two-pion distribution amplitude (DA), we argue that the second Gegenbauer moment, the ρ-meson DA (a2(ρ)), is most probably negative. This result is at variance with the majority of the model calculations for a2(ρ). Using the instanton theory of the QCD vacuum, we computed a2(ρ) at a low normalization point and obtain for the ratio a2(ρ)/M3(π) a definitely negative value in the range of a2(ρ)/M3(π)∈[−2,−1]. The range of values corresponds to a generous variation of the parameters of the instanton vacuum. The value of the second Gegenbauer moment of pion DA is positive in the whole range and is compatible with its the most advanced lattice measurement. It seems that the topologically nontrivial field configurations in the QCD vacuum (instantons) lead to qualitatively different shapes of the pion and the ρ-meson DAs. |
| Databáze: | OpenAIRE |
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