1. P. Fayet, U-boson production in e
+
e
− annihilations, ψ and Y decays and light dark matter, Phys. Rev. D 75 (2007) 115017 [
hep-ph/0702176
] [
INSPIRE
].
2. M. Pospelov, Secluded U(1) below the weak scale, Phys. Rev. D 80 (2009) 095002 [
arXiv:0811.1030
] [
INSPIRE
].
3. J.D. Bjorken, R. Essig, P. Schuster and N. Toro, New fixed-target experiments to search for dark gauge forces, Phys. Rev. D 80 (2009) 075018 [
arXiv:0906.0580
] [
INSPIRE
].
4. R. Essig et al., Working group report: new light weakly coupled particles,
arXiv:1311.0029
[
INSPIRE
].
5. J. Alexander et al., Dark sectors 2016 workshop: community report,
arXiv:1608.08632
[
INSPIRE
].