Probing Minimal Supergravity at the CERN LHC for Large $\tanβ$

Abstract

For large values of the minimal supergravity model parameter $\tanβ$, the tau lepton and the bottom quark Yukawa couplings become large, leading to reduced masses of $τ$-sleptons and $b$-squarks relative to their first and second generation counterparts, and to enhanced decays of charginos and neutralinos to $τ$-leptons and $b$-quarks. We evaluate the reach of the CERN LHC $pp$ collider for supersymmetry in the mSUGRA model parameter space. We find that values of $m_{\tg}\sim 1500-2000$ GeV can be probed with just 10 fb$^{-1}$ of integrated luminosity for $\tanβ$ values as high as 45, so that mSUGRA cannot escape the scrutiny of LHC experiments by virtue of having a large value of $\tanβ$. We also perform a case study of an mSUGRA model at $\tanβ=45$ where $\tz_2\to τ\ttau_1$ and $\tw_1\to \ttau_1ν_τ$ with $\sim 100%$ branching fraction. In this case, at least within our simplistic study, we show that a di-tau mass edge, which determines the value of $m_{\tz_2}-m_{\tz_1}$, can still be reconstructed. This information can be used as a starting point for reconstructing SUSY cascade decays on an event-by-event basis, and can provide a strong constraint in determining the underlying model parameters. Finally, we show that for large $\tanβ$ there can be an observable excess of $τ$ leptons, and argue that $τ$ signals might serve to provide new information about the underlying model framework.