  A search for quark compositeness in the form of quark contact interactions,
based on hadronic jet pairs (dijets) produced in proton-proton collisions at
sqrt(s)=7 TeV, is described. The data sample of the study corresponds to an
integrated luminosity of 2.9 inverse picobarns collected with the CMS detector
at the LHC. The dijet centrality ratio, which quantifies the angular
distribution of the dijets, is measured as a function of the invariant mass of
the dijet system and is found to agree with the predictions of the Standard
Model. A statistical analysis of the data provides a lower limit on the energy
scale of quark contact interactions. The sensitivity of the analysis is such
that the expected limit is 2.9 TeV; because the observed value of the
centrality ratio at high invariant mass is below the expectation, the observed
limit is 4.0 TeV at the 95% confidence level.
