Tracking down the elusive charginos / neutralinos through $\tau$ leptons at the Large Hadron Collider

TL;DR

This paper explores how specific tau-lepton signals at the LHC can improve the detection of charginos and neutralinos in a minimal supersymmetric model with a heavy strongly interacting sector and a light electroweak sector.

Contribution

It demonstrates that tau-jet and lepton signals can significantly extend chargino-neutralino search reach at the LHC, especially with certain decay modes, in a well-motivated supersymmetric scenario.

Findings

Tau-jet + 2 leptons and 2 tau-jets + 1 lepton signals enhance detection prospects.

These signals are more effective with large branching ratios for leptonic decays.

Standard mSUGRA models do not support these signals, but alternative boundary conditions do.

Abstract

An unconstrained minimal supersymmetric standard model with the superpartners of the strongly interacting particles very heavy (close to the kinematic reach of the LHC or even beyond it) and a relatively light electroweak sector is considered. Using the event generator Pythia it is shown that the 1$\tau$-jet (tagged) + 2$l$ and 2$\tau$-jets (tagged) + 1$l$ signals with a reasonably hard $\etslash$ spectrum either by themselves or in combination with the conventional $3l$ signal, which is known to be of rather modest size with a soft $\etslash$ spectrum, may appreciably extend the reach of chargino-neutralino search at the LHC with 10 fb$^{-1}$ of integrated luminosity. This is especially so if the lighter chargino and the second lightest neutralino decays via two body leptonic modes with large BRs. The theoretical motivation of this scenario, yielding large values of the fine-tuning parameters but consistent with various indirect constraints including the dark matter relic density, is briefly discussed. It is shown that in the minimal supergravity (mSUGRA) model with an universal scalar mass at the GUT scale, the signals involving $\tau$-jets are not viable. Theoretically well-motivated variations of these boundary conditions are, however, adequate for reviving these signals.