Search for a scalar or vector particle decaying into Zγ in pp̅ collisions at √s = 1.96 TeV

Abstract We present a search for a narrow scalar or vector resonance decaying into Zγ with a subsequent Z boson decay into a pair of electrons or muons. The data for this search were collected with the DO detector at the Fermilab Tevatronp p ¯ collider at a center of mass energy s = 1.96 TeV . Using 1.1 (1.0) fb −1 of data, we observe 49 (50) candidate events in the electron ( muon) channel, in good agreement with the standard model prediction. From the combination of both channels, we derive 95% C.L. upper limits on the cross section times branching fraction( σ × B ) into Zγ . These limits range from 0.19 (0.20) pb for a scalar (vector) resonance mass of 600 GeV / c 2 to 2.5 (3.1) pb for a mass of 140 GeV / c 2 .