Down Type Isosinglet Quarks in ATLAS

We evaluate the discovery reach of the ATLAS experiment for down type isosinglet quarks, $D$, using both their neutral and charged decay channels, namely the process $pp\to D\bar{D}+X$ with subsequent decays resulting in $2\mathrm{\ell }+2j+E_T^{miss}$, $3\mathrm{\ell }+2j+E_T^{miss}$ and $2\mathrm{\ell }+4j$ final states. The integrated luminosity required for observation of a heavy quark is estimated for a mass range between 600 and 1000 GeV using the combination of results from different search channels.