Implications of a Running Dark Photon Coupling

Abstract

For an "invisible" dark photon $Z_d$ that dominantly decays into dark states, the running of its fine structure constant ${\alpha }_d$ with momentum transfer $q>m_{Z_d}$ could be significant. A similar running in the kinetic mixing parameter ${\epsilon }^2$ can be induced through its dependence on ${\alpha }_d(q)$. The running of couplings could potentially be detected in "dark matter beam" experiments, for which theoretical considerations imply ${\alpha }_d(m_{Z_d})\lesssim 0.5$.

Comments: 4 pages, 4 figures. Contributed to the 11th Patras Workshop on Axions, WIMPs and WISPs, Zaragoza, Spain, June 22-26, 2015