Search for Excited Quarks in $q\bar{q}\to \gamma \gamma$ at the LHC

If quarks are composite particles, then excited states are expected to play a r^ole in the Large Hadron Collider phenomena. Concentrating on virtual effects, and using a large part of the CMS detection criteria, we present here a realistic examination of their effect in diphoton production at the LHC. For various luminosities, we present the 99 % confidence limit (CL) achievable in $\mathrm{\Lambda }-M_{q\ast }$ parameter space where $\mathrm{\Lambda }$ is the compositeness scale and M_{q^} the mass of the state. For a q^ of mass 0.5 TeV, $\Lambda \leq 1.55 (2.95)$canbeexcludedat99${\rm fb}^{-1}$ integrated luminosity.