The total di-muon cross section after applying the above preselection cuts is then $\sigma_{\rm B}\simeq 25{\ensuremath{\,\textnormal{pb}}}$.

(0.95,0.53) (0.51,0.03)[![Left: Pseudorapidity distribution of the considered di-muon background after applying the preselection cuts, where $\eta^\pm$ denotes the pseudorapidity of $\mu^\pm$. Right: Total di-muon cross section after applying the preselection cuts but as a function of the variable ${p_\text{T}}$-cut discussed at the end of section \[sec:Discovery\] (again on both muons). Both plots are valid for the $14{\ensuremath{\,\textnormal{TeV}}}$ LHC.[]{data-label="fig:dimu"}](sigma-dimu-ptcut-fit.eps "fig:")]{} (0.49,0.219) (0.697,0.0)[${p_\text{T}}^\text{min}\;[$GeV$]$]{} (-0.013,-0.0093)[ (0.7,0.4122)[generated via MadEvent/]{} (0.7,0.385)[Pythia]{} (0.7,0.352)[conservative fit for ]{} (0.7,0.327)[${p_\text{T}}>50{\ensuremath{\,\textnormal{GeV}}}$]{} ]{} (-0.002,0.03)[![Left: Pseudorapidity distribution of the considered di-muon background after applying the preselection cuts, where $\eta^\pm$ denotes the pseudorapidity of $\mu^\pm$. Right: Total di-muon cross section after applying the preselection cuts but as a function of the variable ${p_\text{T}}$-cut discussed at the end of section \[sec:Discovery\] (again on both muons). Both plots are valid for the $14{\ensuremath{\,\textnormal{TeV}}}$ LHC.[]{data-label="fig:dimu"}](mu-eta-eta.eps "fig:")]{} (-0.027,0.235) (0.227,0.0)[$|\eta^-|$]{}

### Velocity measurement {#velocity-measurement .unnumbered}

The crucial tool for distinguishing muons from staus is the velocity measurement. A significant fraction of staus with a mass of several hundred GeV will have a velocity well below the speed of light, whereas the background muons are always ultra-relativistic. Unfortunately, measuring the velocity is much 