A study of SUSY signatures at the Tevatron in models with near mass degeneracy of the lightest chargino and neutralino

TL;DR

This paper investigates the detection prospects of nearly degenerate chargino and neutralino in supersymmetry models at the Tevatron, focusing on unique signatures like disappearing tracks and their dependence on mass differences and gluino mass.

Contribution

It introduces new detection strategies for nearly degenerate chargino-neutralino scenarios at the Tevatron, analyzing their effectiveness and mass reach.

Findings

Detection sensitivity depends on mass difference between chargino and neutralino.

Longer chargino lifetimes produce distinctive disappearing tracks.

Tevatron can potentially observe signals even with heavy gluinos.

Abstract

For some choices of soft SUSY-breaking parameters, the LSP is a stable neutralino $\cnone$, the NLSP is a chargino $\cpmone$ almost degenerate in mass with the LSP ($\dmchi\equiv\mcpmone-\mcnone\sim \mpi-$few GeV), and all other sparticles are relatively heavy. In this case, detection of sparticles in the usual, mSUGRA-motivated signals will be difficult, since the decay products in $\cpmone\to\cnone...$ will be very soft, and alternative signals must be considered. Here, we study the viability of signatures at the Tevatron based on highly-ionizing charged tracks, disappearing charged tracks, large impact parameters, missing transverse energy and a jet or a photon, and determine the mass reach of such signatures assuming that only the $\cpmone$ and $\cnone$ are light. We also consider the jet+$\etmiss$ and $\gamma+\etmiss$ signatures assuming that the gluino is also light with $\mgl\sim \mcpmone$. We find that the mass reach is critically dependent upon $\dmchi$ and $\mgl-\mcpmone$. If $\dmchi$ is sufficiently big that $c\tau(\cpmone)\lsim$few cm and $\mgl$ is large, there is a significant possibility that the limits on $\mcpmone$ based on LEP2 data cannot be extended at the Tevatron. If $c\tau(\cpmone)>$few cm, relatively background-free signals exist that will give a clear signal of $\cpmone$ production (for some range of $\mcpmone$) even if $\mgl$ is very large.