Search for Stopped Gluinos from $p\overline{p}$ Collisions at $\sqrt{s}=1.96\mathrm{TeV}$

Long-lived, heavy particles are predicted in a number of models beyond the standard model of particle physics. We present the first direct search for such particles’ decays, occurring up to 100 h after their production and not synchronized with an accelerator bunch crossing. We apply the analysis to the gluino ($\tilde{g}$), predicted in split supersymmetry, which after hadronization can become charged and lose enough momentum through ionization to come to rest in dense particle detectors. Approximately $410{\mathrm{pb}}^{-1}$ of $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ collected with the D0 detector during Run II of the Fermilab Tevatron collider are analyzed in search of such “stopped gluinos” decaying into a gluon and a neutralino (${\tilde{\chi }}_1^0$). Limits are placed on the $(\mathrm{\text{gluino cross section}})\times (\mathrm{\text{probability to stop}})\times [\mathrm{BR}(\tilde{g}\to g{\tilde{\chi }}_1^0)]$ as a function of the gluino and ${\tilde{\chi }}_1^0$ masses, for gluino lifetimes from $30\mu \mathrm{s}–100\mathrm{h}$.

Figure 1

A comparison of the wide-shower no-muon data (points) to the expected background from cosmic muons (solid histogram) and a simulated signal (dashed histogram).

Figure 2

Left: the trigger efficiency vs gluino lifetime. Right: the instantaneous luminosity profile used to model the trigger efficiency. Dashed lines indicate a 50% chance of the store occurring.

Figure 3

Top: the expected and observed upper limits on the cross section of stopped gluinos, assuming a 100% BR of $\tilde{g}\to g{\tilde{\chi }}_1^0$ and a small gluino lifetime ($<3\mathrm{h}$), for three choices of the ${\tilde{\chi }}_1^0$ mass: 50, 90, and 200 GeV, from left to right. Bottom: the upper limits observed on the cross section of stopped gluinos, for various assumptions of the gluino lifetime, for a ${\tilde{\chi }}_1^0$ mass of 50 GeV. Also shown are the theoretical stopped gluino cross sections (dashed lines, shaded area), from Ref. [4], for the range of assumed conversion cross sections.