We report mass limits on the Z° and W ± , supersymmetric partners of the Z° and W ± , respectively, using the MARK-J detector at PETRA. The experimental signatures in both cases are acoplanar lepton pairs with missing energy. For the W~, an additional signature is a single energetic lepton. No evidence is found for either the Z° (M^0< 35 GeV) or the W ± (M^<25GeV).PACS numbers: 14.80.Pb, 13.10.+q The standard electroweak theory 1 predicts the existence of charged (W ± ) and neutral (Z°) vector gauge bosons. These particles were recently discovered at the CERN pp collider 2 and the measured masses (M w^& 2 GeV, M z0 -93 GeV) agree with predictions. Earlier experiments at PE-TRA 3 ' 4 and PEP 5 have measured the forwardbackward charge asymmetry in the reaction e + e~ -+ /JL + JJL~ and found it to be consistent with the interference between the photon and the Z° as exchanged intermediate particles. They placed limits on the Z° mass. Final states with leptons can also be analyzed to search for effects not covered in the standard theory. The success of the electroweak theory leads naturally to the development of theories that offer explanations of the roles of the strong and gravitational interactions, the source of the masses of the gauge particles, and the existence of other bosons. Supersymmetric models 6 have been developed to resolve some of these problems. It has recently been suggested that supersymmetric grand-unified models based on supergravity predict the existence of a neutral spin-y fermion, the Z-ino (Z°), which is a partner to the Z°, and a charged spin-y fermion, the W-ino ( W ± ), which is a partner to the W ± . More specifically, the least massive Z-ino and W-ino are expected, in some models, 7-9 to have masses less than those of the Z° and the W ± , respectively, and in the model of Ref. 9 to have masses less than half of their partner bosons.The Z-ino could be produced in e + e~ annihilation via an exchange of a scalar electron, e :e + e--+y + Z° ,where the y is the spin-y partner of the photon. If the y is lighter than the Z °, a possible Z ° decay iswhere 7 is the supersymmetric scalar partner of a charged lepton. The total cross section 9 for single Z-ino production depends on the masses of the scalar electron, the Z-ino, and the photino (y). For M 2 ==35 GeV, M~e^40 GeV, and Af.=^2 GeV the total cross section is estimated to be about 3 pb at cm. energy -Js -44 GeV. 9 This is large enough for detection since the events are expected to have distinctive features. The lifetime of the Z ° is estimated to be in the range 10" 16 to 10~2 0 sec with the e* e~ y branching ratios 10 each of the order of 10%. Our previous measure-+ y or /A + JH 1806
