Pion Distribution Amplitudes from Functional QCD
arXiv:2607.04871
The authors compute the pion distribution amplitude from first‑principles QCD using the functional renormalisation group combined with large‑momentum effective theory, obtaining a quasi‑DA at high pion momentum and a second‑order moment consistent with other nonperturbative approaches.
Abstract
We present the first functional QCD calculation of the pion distribution amplitude (DA) using the large-momentum effective theory within the functional renormalisation group (fRG) approach. With only the strong coupling and current quark masses as inputs, we compute the quasi-DA from first-principles QCD correlation functions. By pushing the pion momentum up to , the quasi-DA becomes fully saturated, rendering the extrapolation errors to the light-cone limit negligible. The resulting second-order moment is significantly smaller than existing lattice-LaMET determinations and lies in a range consistent with other nonperturbative approaches.
17 pages, 11 figures, 2 tables; v2: Added references and corrected minor typos