Search for Long-Lived Massive Charged Particles in 1.96 TeV $p\overline{p}$ Collisions

We performed a signature-based search for long-lived charged massive particles produced in $1.0{\mathrm{fb}}^{-1}$ of $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$, collected with the CDF II detector using a high transverse-momentum ($p_T$) muon trigger. The search used time of flight to isolate slowly moving, high-$p_T$ particles. One event passed our selection cuts with an expected background of $1.9\pm 0.2$ events. We set an upper bound on the production cross section and, interpreting this result within the context of a stable scalar top-quark model, set a lower limit on the particle mass of $249\mathrm{GeV}/c^2$ at 95% C.L.

Figure 1

Observed (histogram) and predicted (band) mass distributions for candidate tracks in the muon sample. The curves on the right show the MC distributions expected for a 140 and a $220\mathrm{GeV}/c^2$ long-lived top squark.

Figure 2

The observed 95% C.L. limits on the cross section for production of a stable top-squark pair (triangles), compared to the theoretical next-to-leading-order cross section [12] (curve). The band represents theoretical and parton distribution function uncertainties. The intersection of the band with the limit curve yields a lower mass limit for a stable top squark of $249\mathrm{GeV}/c^2$.