Charginos and Neutralinos in the Light of Radiative Corrections: Sealing the Fate of Higgsino Dark Matter

We analyze the LEP constraints from searches for charginos ${\chi }^{\pm }$ and neutralinos ${\chi }_i$, taking into account radiative corrections to the relations between their masses and the underlying Higgs-mixing and gaugino-mass parameters $\mu ,m_{1\mathrm{/}2}$ and the trilinear mass parameter $A_t$. Whilst radiative corrections do not alter the excluded domain in $m_{{\chi }^{\pm }}$ as a function of $m_{{\chi }^{\pm }}-m_{\chi }$, its mapping into the $\mu ,m_{1\mathrm{/}2}$ plane is altered. We update our previous lower limits on the mass of gaugino dark matter and on tan$\beta$, the ratio of Higgs vacuum expectation values, in the light of the latest LEP data and these radiative corrections. We also discuss the viability of Higgsino dark matter, incorporating co-annihilation effects into the calculation of the Higgsino relic abundance. We find that Higgsino dark matter is viable for only a very limited range of $\mu$ and $m_{1\mathrm{/}2}$, which will be explored completely by upcoming LEP runs.