We derive new constraints on light vectors coupled to standard model (SM) fermions, when the corresponding SM current is broken by the chiral anomaly. The cancellation of the anomaly by heavy fermions results, in the low-energy theory, in Wess-Zumino-type interactions between the new vector and the SM gauge bosons. These interactions are determined by the requirement that the heavy sector preserves the SM gauge groups and lead to (energy/vector mass)2 enhanced rates for processes involving the longitudinal mode of the new vector. Taking the example of a vector coupled to a vector coupled to SM baryon number, Z decays and flavor-changing neutral current meson decays via the new vector can occur with (weak scale/vector mass)2 enhanced rates. These processes place significantly stronger coupling bounds than others considered in the literature, over a wide range of vector masses.
Bibliographical noteFunding Information:
We thank Masha Baryakhtar, Jesse Thaler, and Yue Zhao for helpful discussions. Research at Perimeter Institute is supported by the Government of Canada through Industry Canada and by the Province of Ontario through the Ministry of Economic Development and Innovation.