Observation of a diffractive contribution to dijet production in proton-proton collisions at $\sqrt{s} = 7$~TeV

The differential cross section measurement for dijet production at proton-proton collisions at $\sqrt{s}=7$ TeV is presented as a function of an approximation for the fractional momentum loss of the scattered proton ($\tilde{\xi}$), an useful observable to distinguish model predictions of diffractive and nondiffractive components. The data was collected by the CMS detector at low instantaneous luminosity runs at LHC, corresponding to an integrated luminosity of $2.7 {\rm nb}^{-1}$. This is the first observation of single diffractive dijets at LHC.