Lepton energy asymmetry and precision supersymmetry study at hadron colliders

We study the distribution of lepton pairs from the second lightest neutralino decay ${\tilde{\chi }}_2^0\to \tilde{l}l$ followed by $\tilde{l}\to {\tilde{\chi }}_1^{0}l.\mathrm{}$ The distribution of the ratio of lepton transverse momenta $A_T$ shows a peak structure if $m_{\mathrm{ll}}\lesssim m_{\mathrm{ll}}^{\max }/2\mathrm{}$ is required. The peak position $A_T^{\mathrm{peak}}$ is described by a simple function of the gaugino and slepton masses in the $m_{\mathrm{ll}}\sim 0$ limit. When a moderate $m_{\mathrm{ll}}$ cut is applied, the $A_T^{\mathrm{peak}}$ depends on the ${\tilde{\chi }}_2^0$ velocity distribution, but the dependence would be corrected by studying the lepton $P_T$ distribution. $A_T^{\mathrm{peak}}$ and the edge of $m_{\mathrm{ll}}$ distributions are used to determine the mass parameters involved in the decay for parameters of interest to CERN Large Hadron Collider experiments. For some cases the gaugino and slepton masses may be determined within 10% by the lepton distribution only independent of model assumptions. Correct combinations of $A_T^{\mathrm{peak}}$ and $m_{\mathrm{ll}}^{\mathrm{edge}}$ would be identified even if different ${\tilde{\chi }}_2^0$ decay chains are coexisting. The analysis could be extended to the Fermilab Tevatron energy scale or other cascade decays.