Trileptons from Chargino-Neutralino Production at the CERN Large Hadron Collider

Abstract

We study direct production of charginos and neutralinos at the CERN Large Hadron Collider. We simulate all channels of chargino and neutralino production using ISAJET 7.07. The best mode for observing such processes appears to be $pp\to\tw_1\tz_2\to 3\ell +\eslt$. We evaluate signal expectations and background levels, and suggest cuts to optimize the signal. The trilepton mode should be viable provided $m_{\tg}\alt 500-600$~GeV; above this mass, the decay modes $\tz_2\to\tz_1 Z$ and $\tz_2\to H_{\ell}\tz_1$ become dominant, spoiling the signal. In the first case, the leptonic branching fraction for $Z$ decay is small and additional background from $WZ$ is present, while in the second case, the trilepton signal is essentially absent. For smaller values of $m_{\tg}$, the trilepton signal should be visible above background, especially if $|\mu|\simeq m_{\tg}$ and $m_{\tell}\ll m_{\tq}$, in which case the leptonic decays of $\tz_2$ are enhanced. Distributions in dilepton mass $m(\ell\bar{\ell})$ can yield direct information on neutralino masses due to the distribution cutoff at $m_{\tz_2}-m_{\tz_1}$. Other distributions that may lead to an additional constraint amongst the chargino and neutralino masses are also examined.