Search for new phenomena in events with two $Z$ bosons and missing transverse momentum in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV.

Abstract

WepresentasearchfornewphenomenaineventswithtworeconstructedZbosonsandlargemissing transversemomentum,sensitivetoprocessespp!X2X2 !ZZX1X1,whereX2isanunstableparticle decayingasX2 !ZX1andX1isundetected.TheparticlesX1andX2maybe,amongotherpossibilities, fourth-generationneutrinosorsupersymmetricparticles.WestudythefinalstateinwhichoneZboson decaystotwochargedleptonsandtheseconddecayshadronically.Indatacorrespondingtoanintegrated luminosityof4:2fb1fromproton-antiprotoncollisionsrecordedbytheCDFIIdetectorattheTevatron, withcenter-of-massenergyof1.96TeV,wefindagreementbetweendataandstandard-modelbackgrounds. Wecalculate95%confidencelevelupperlimitsonthecrosssectionoftheprocesspp! X2X2 !ZZX1X1rangingfrom50fbto1pb,dependingonthemassesofX1andX2.