Constraining the minimal supergravity model parameter tan(beta) by measuring the dilepton mass distribution at LHC

Abstract

We study the dependence on $\tan \beta$ of the event kinematics of final states with $e^{+}{e}^{-}/{\mu }^{+}{\mu }^{-}/e^{\pm }{\mu }^{\mp }+E_T^{\mathrm{miss}}+jets$, as expected in $pp$ collisions at CERN LHC, within the framework of the minimal supergravity model. With increase of $\tan \beta$, the third generation sparticle masses $m_{{\tilde{\tau }}_1}$ and $m_{{\tilde{b}}_1}$ decrease due to the increase of the tau and bottom Yukawa couplings. As a result, gluino, stop, sbottom, chargino and neutralino decays to third generation particles and sparticles are enhanced. With $\tan \beta$ rising, we observe a characteristic change in the shape of the dilepton mass spectra in $e^{+}{e}^{-}/{\mu }^{+}{\mu }^{-}+E_T^{\mathrm{miss}}+jets$ versus $e^{\pm }{\mu }^{\mp }+E_T^{\mathrm{miss}}+jets$ final states, 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 ${\tilde{\chi }}_2^0\to {\tilde{\tau }}_1^{\pm }{\tau }^{\mp }\to {\tilde{\chi }}_1^0{\tau }^{+}{\tau }^{-}$, ${\tilde{\chi }}_2^0\to {\tau }^{+}{\tau }^{-}{\tilde{\chi }}_1^0$, respectively. We exploit this effect for constraining the value of $\tan \beta$.

Comments: 16 page latex file including 5 eps figures