Is there a vector boson coupling to baryon number?

Discrepancies in measurements of the QCD running coupling constant are consistent with a new vector gauge boson coupling to baryon number with strength βB ∼ 0.1. Upsilon decays constrain such a boson to have a mass greater than about 35 GeV. It is difficult to observe such a boson in Z decays, e+e− annihilation, or hadronic interactions.