CMS collaboration (2263 authors)Hollar, JonathanAlmeida, NunoBargassa, PedrameDavid Tinoco Mendes, AndreFaccioli, PietroFerreira Parracho, Pedro GuilhermeGallinaro, MicheleMusella, PasqualeNayak, ArunaPela, JoaoRibeiro, Pedro QuinazSeixas, JoaoVarela, JoaoLloret Iglesias, LaraRodrigues Antunes, JoaoSilva, PedroLeonardo, Nuno2019-02-032019-02-032012-01http://dx.doi.org/10.1007/JHEP01(2012)133http://hdl.handle.net/10400.26/26055The integrated and differential cross sections for the production of pairs of isolated photons is measured in proton-proton collisions at a centre-of-mass energy of 7 TeV with the CMS detector at the LHC. A data sample corresponding to an integrated luminosity of 36 inverse picobarns is analysed. A next-to-leading-order perturbative QCD calculation is compared to the measurements. A discrepancy is observed for regions of the phase space where the two photons have an azimuthal angle difference, $\Delta(\phi)$, less than approximately 2.8.engjournal article2019-02-03