  In this work, we study the light stop pair signals at the large hadron
collider (LHC) in three coannihilation scenarios. In order to yield the desired
dark matter (DM) relic density, the neutralino can coannihilate with stop,
chargino and stau, respectively. Signatures of the first scenario can be probed
at the LHC via the associated jet production processes $pp \to j + {\tilde t}
{\tilde t}^*$ by tagging an energetic mono-jet and a large missing transverse
energy. The signatures of the other two scenarios can be searched via the pair
production process $pp \to {\tilde t} {\tilde t}^*$ by tagging energetic b-jets
in the final states and a large missing transverse energy. We find that the LHC
results at 7 TeV with 5 $\mathrm{fb}^{-1}$ of data can exclude the stop mass up
to 220, 380 and 220 GeV for these three scenarios, respectively. While the 20
$\mathrm{fb}^{-1}$ dataset at 8 TeV is considered, the LHC can be expected to
exclude the stop mass up to 340, 430 and 370 GeV.
