Constraining the minimal supergravity model parametertanβby measuring the dilepton mass distribution at CERN LHC

We study the dependence on $\tan\beta$ of the event kinematics of finalstates with $e^+e^- /\mu^+\mu^- /e^{\pm}\mu^{\mp} + E_T^{\rm miss} + jets$, asexpected in $pp$ collisions at CERN LHC, within the framework of the minimalsupergravity model. With increase of $\tan\beta$, the third generationsparticle masses $m_{\tilde{\tau}_1}$ and $m_{\tilde{b}_1}$ decrease due to theincrease of the tau and bottom Yukawa couplings. As a result, gluino, stop,sbottom, chargino and neutralino decays to third generation particles andsparticles are enhanced. With $\tan\beta$ rising, we observe a characteristicchange in the shape of the dilepton mass spectra in $e^+e^- /\mu^+\mu^-+E_T^{\rm miss} + jets$ versus $e^{\pm}\mu^{\mp} + E_T^{\rm miss} + jets$ finalstates, reflecting the presence of the decays $\tilde{\chi}_2^0\to\tilde{\ell}_{L,R}^{\pm}\ell^{\mp}\to \tilde{\chi}_1^0 \ell^+\ell^-,\tilde{\chi}_2^0\to \tilde{\chi}_1^0 \ell^+\ell^-$ and $\tilde{\chi}_2^0\to\tilde{\tau}^{\pm}_1\tau^{\mp}\to \tilde{\chi}_1^0 \tau^+ \tau^-$,$\tilde{\chi}_2^0\to \tau^+ \tau^- \tilde{\chi}_1^0$, respectively. We exploitthis effect for constraining the value of $\tan\beta$.Comment: 16 page latex file including 5 eps figure