First search for exotic Z boson decays into photons and neutral pions in hadron collisions

Abstract

A search for forbidden and exotic Z boson decays in the diphoton mass spectrum is presented for the first time in hadron collisions, based on data corresponding to 10.0fb-1 of integrated luminosity from proton-antiproton collisions at s=1.96TeV collected by the CDF experiment. No evidence of signal is observed, and 95% credibility level Bayesian upper limits are set on the branching ratios of decays of the Z boson to a photon and neutral pion (which is detected as a photon), a pair of photons, and a pair of neutral pions. The observed branching ratio limits are 2.01×10-5 for Z→π0γ, 1.46×10-5 for Z→γγ, and 1.52×10-5 for Z→π0π0. The Z→π0γ and Z→γγ limits improve the most stringent results from other experiments by factors of 2.6 and 3.6, respectively. The Z→π0π0 branching ratio limit is the first experimental result on this decay. © 2014 American Physical Society.