Search for new particles decaying into dijets in proton-proton collisions at sqrt{s} = 7 TeV with the ATLAS detector

A search for new heavy particles manifested as narrow dijet (two-jet) invariant mass resonances is presented using the ATLAS detector to study proton-proton collisions at a centre-of-mass energy of sqrt{s} = 7 TeV. The data were collected during the April - July 2010 period of Large Hadron Collider (LHC) operations and correspond to a time-integrated luminosity of 296 nb^{-1}. No significant evidence of new particles was found in this preliminary sample. Upper limits were set on the products of cross section and detector acceptance for hypothetical new particles expected to decay into dijets, for which each jet was reconstructed with a pseudorapidity |eta| < 2.5. These limits were used with a theoretical prediction for excited-quark production to determine a 95% credibility-level q* mass exclusion region of 400 < m_{q*} < 1290 GeV for the case where MRST2007 parton distribution functions were considered.