Light Higgsino Detection at LEP1.5

Within the minimal supersymmetric extension of the Standard Model, the best fit to the most recent precision-measurement data requires charginos and neutralinos, with dominant Higgsino components and with masses within the reach of LEP1.5 ($\sqrt{s}=140$ GeV). In this work, we present a detailed analysis of the neutralino and chargino production processes for the favoured region of parameter space, that is low values of $|\mu|$ and either low or large values of $\tan\beta$. We find that chargino and neutralino searches can cover the Higgsino region in the ($\mu,M_2$) plane for values of $M_2 \simlt 1$ TeV, at the next phases of the LEP collider. We also show that, due mainly to phase-space constraints, the lightest neutralinos should be more easily detectable than charginos in most of the parameter space preferred by precision-measurement data.