Measurement of the photon identification efficiencies with the ATLAS detector using LHC Run-1 data

• Main Author: ATLAS collaboration (2856 authors)
• Publication Date: 2016
• Other Authors: Aguilar-Saavedra, Juan Antonio, Amor Dos Santos, Susana Patricia, Anjos, Nuno, Araque, Juan Pedro, Cantrill, Robert, Carvalho, João, Castro, Nuno Filipe, Conde Muiño, Patricia, Da Cunha Sargedas De Sousa, Mario Jose, Fiolhais, Miguel, Galhardo, Bruno, Gomes, Agostinho, Gonçalo, Ricardo, Jorge, Pedro, Lopes, Lourenco, Machado Miguens, Joana, Maio, Amélia, Maneira, José, Oleiro Seabra, Luis Filipe, Onofre, António, Palma, Alberto, Pedro, Rute, Santos, Helena, Saraiva, João, Silva, José, Tavares Delgado, Ademar, Veloso, Filipe, Wolters, Helmut
• Format: Article
• Language: eng
• Source: Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
• Download full: http://dx.doi.org/10.1140/epjc/s10052-016-4507-9; http://hdl.handle.net/10400.26/27102

The algorithms used by the ATLAS Collaboration to reconstruct and identify prompt photons are described. Measurements of the photon identification efficiencies are reported, using 4.9 fb$^{-1}$ of pp collision data collected at the LHC at $\sqrt{s} = 7$   $\text {TeV}$ and 20.3 fb$^{-1}$ at $\sqrt{s} = 8$   $\text {TeV}$ . The efficiencies are measured separately for converted and unconverted photons, in four different pseudorapidity regions, for transverse momenta between 10  $\text {GeV}$ and 1.5  $\text {TeV}$ . The results from the combination of three data-driven techniques are compared to the predictions from a simulation of the detector response, after correcting the electromagnetic shower momenta in the simulation for the average differences observed with respect to data. Data-to-simulation efficiency ratios used as correction factors in physics measurements are determined to account for the small residual efficiency differences. These factors are measured with uncertainties between 0.5% and 10% in 7  $\text {TeV}$ data and between 0.5% and 5.6% in 8  $\text {TeV}$ data, depending on the photon transverse momentum and pseudorapidity.