The distribution amplitude of the ${\eta }_c$ meson

Abstract

We report on the first lattice determination of the pseudoscalar meson ${\eta }_c$ light-cone distribution amplitude, using a set of three CLS $N_f=2$ ensembles at a pion mass $m_{\pi }\sim 270\text{MeV}$ and lattice spacings $a\sim 0.076\text{fm}$, $0.066\text{fm}$ and $0.049\text{fm}$. Employing Short Distance Factorization, we extract the pseudo-DA on the lattice for Ioffe times $\nu \le 4.5$, and the various lattice spacings allow us to take the continuum limit. We employ a basis of Jacobi polynomials to parametrize the distribution amplitude, which allows to express the matching to the pseudo distribution in closed form, and we observe a strong effect which we attribute to the heavy charm-quark mass.

Comments: Contribution to the 40th International Symposium on Lattice Field Theory (Lattice 2023), July 31st - August 4th, 2023. Fermi National Accelerator Laboratory