Mini Force: the (B-L) + xY gauge interaction with a light mediator
  The relevant phenomenology and the best search schemes of a subelectroweak-scale gauge boson can be vastly different depending on its coupling. For instance, the rare decay into a light gauge boson and the high precision parity test can be sensitive if it has an axial coupling. The minimal gauge extension of the standard model with the U(1)_{B-L + xY} requires only three right-handed neutrinos, well-suited to the current neutrino mass and mixing data, and no additional exotic matter fields. We study the light gauge boson of this symmetry in detail including its axial coupling property from the hypercharge shift. 
Hye-Sung Lee, Seokhoon Yun
hep-ph