We calculate the two-loop quarkonium Hamiltonian in the annihilation channel within the framework of potential-NRQCD effective field theory. The result agrees with the previous calculation of the corresponding four-quark operator in NRQCD for SU(N) color gauge group. We further obtain an expression with a more general color structure applicable to other gauge groups. Combined with the recently calculated two-loop Hamiltonian in the non-annihilation channel, this completes the full two-loop quarkonium Hamiltonian.
Cite
@article{arxiv.2604.23303,
title = {Two-loop quarkonium Hamiltonian in annihilation channel},
author = {Yukinari Sumino and Takahiro Ueda},
journal= {arXiv preprint arXiv:2604.23303},
year = {2026}
}