In the family grand unification models (fGUTs), we propose that gauge U(1)'s beyond the minimal GUT gauge group are family gauge symmetries. For the symmetry Lμ−Lτ, i.e. Q2−Q3 in our case, to be useful for the LHC anomaly, we discuss an SU(9) fGUT and also present an example in Georgi's SU(11) fGUT.
@article{arxiv.2004.08234,
title = {$L_{\mu}-L_{\tau}$ effects to quarks and leptons from flavor unification},
author = {Paul H. Frampton and Sin Kyu Kang and Jihn E. Kim and Soonkeon Nam},
journal= {arXiv preprint arXiv:2004.08234},
year = {2020}
}