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Spires | arXiv:1311.1440 [hep-ex] | Phys.Rev. D89 (2014) 052004

A measurement of the cross section for the production of isolated prompt photons in pp collisions at a center-of-mass energy $sqrt{s} = 7$ TeV is presented. The results are based on an integrated luminosity of 4.6 fb$^{-1}$ collected with the ATLAS detector at the LHC. The cross section is measured as a function of photon pseudorapidity $\eta^\gamma$ and transverse energy $E_T^\gamma$ in the kinematic range $100 < E_T^\gamma < 1000$ GeV and in the regions $|\eta^\gamma| < 1.37$ and $1.52 < |\eta^\gamma| < 2.37$. The results are compared to leading-order parton-shower Monte Carlo models and next-to-leading order perturbative QCD calculations. Next to-leading-order perturbative QCD calculations agree well with the measured cross sections as a function of $E_T^\gamma$ and $\eta^\gamma$.

Spires | Nucl.Phys. B875 (2013) 483-535 | doi:10.1016/j.nuclphysb.2013.07.025 | arXiv:1307.6795 [hep-ex]

Measurements of isolated photon plus jet production in $pp$ collisions at a centre-of-mass energy of 7 TeV with the ATLAS detector at the LHC using an integrated luminosity of $37 \text{pb}^{-1}$. Differential cross sections are presented as functions of photon transverse energy, jet transverse momentum and jet rapidity. In addition, the differential cross sections as functions of the difference between the azimuthal angles of the photon and the jet, the photon-jet invariant mass as well as the scattering angle in the photon-jet centre-of-mass frame have been measured.

Spires | arXiv:1211.1913 [hep-ex] | JHEP 1301 (2013) 086

The ATLAS experiment at the LHC has measured the production cross section of events with two isolated photons in the final state, in proton-proton collisions at $\sqrt{s} = 7$ TeV. The full data set collected in 2011, corresponding to an integrated luminosity of 4.9 fb$^{-1}$, is used. The amount of background, from hadronic jets and isolated electrons, is estimated with data-driven techniques and subtracted. The total cross section, for two isolated photons with transverse energies above 25 GeV and 22 GeV respectively, in the acceptance of the electromagnetic calorimeter ($|\eta|<1.37$ and $1.52<|\eta|<2.37$) and with an angular separation $\Delta R>0.4$, is $44.0^{+3.2}_{-4.2}$ pb. The differential cross sections as a function of the di-photon invariant mass, transverse momentum, azimuthal separation, and cosine of the polar angle of the largest transverse energy photon in the Collins--Soper di-photon rest frame are also measured. The results are compared to the prediction of leading-order parton-shower and next-to-leading-order and next-to-next-to-leading-order parton-level generators.

Spires | arXiv:1203.3161 [hep-ex]

A measurement of the production cross section for isolated photons in association with jets in $pp$ collisions at $\sqrt{s} = 7$ TeV. Photons with $|\eta|<1.37$ and $E_T>25$ GeV and jets with $|y|<4.4$ and $p_T>20$ GeV are selected. The differential cross section as a function of the photon transverse energy is measured, for three leading jet rapidity configurations, separately for the cases where the photon and jet rapidities have the same or the opposite sign. The measurement uses 37 pb$^{-1}$ of integrated luminosity collected with the ATLAS detector.

Spires | arXiv:1108.0253 [hep-ex] | Phys.Lett. B706 (2011) 150-167

A measurement of the differential cross-section for the inclusive production of isolated prompt photons in $pp$ collisions at a center-of-mass energy $\sqrt{s} = 7$ TeV is presented. The measurement covers the pseudorapidity ranges $|\eta|<1.37$ and $1.52<|\eta|<2.37$ in the transverse energy range $45<E_T<400$ GeV. The results are based on an integrated luminosity of 35 pb$^{-1}$, collected with the ATLAS detector at the LHC. The yields of the signal photons are measured using a data-driven technique, based on the observed distribution of the hadronic energy in a narrow cone around the photon candidate and the photon selection criteria. The results are compared with next-to-leading order perturbative QCD calculations and found to be in good agreement over four orders of magnitude in cross-section.

Spires | arXiv:1107.0581 [hep-ex]

A measurement of the cross section for inclusive isolated photon production at $\sqrt{s} = 7$ TeV. The measurement is done in bins of $M_{\gamma\gamma}$, $p_{T\gamma\gamma}$, and $\Delta\phi_{\gamma\gamma}$, for isolated photons with $|\eta|<2.37$ and $E_T^\gamma>16$ GeV. The measurement uses 37 pb$^{-1}$ of integrated luminosity collected with the ATLAS detector.

Spires | arXiv:1012.4389 [hep-ex]

A measurement of the cross section for inclusive isolated photon production at $\sqrt{s} = 7$ TeV. The measurement covers three ranges in $|\eta|$: [0.00,0.60), [0.60,1.37), and [1.52,1.81), for $E_T^\gamma>15$ GeV. The measurement uses 880 nb$^{-1}$ of integrated luminosity collected with the ATLAS detector.

Spires | arXiv:1310.3082 | https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsSMP12004 | Submitted to Phys. Rev. Lett

Rapidity distributions are presented for events containing either a $Z$ boson or a photon in association with a single jet in proton-proton collisions produced at the CERN LHC. The data, collected with the CMS detector at $\sqrt{s} = 7$ TeV, correspond to an integrated luminosity of 5.0/fb. The individual rapidity distributions of the boson and the jet are consistent within 5\% with expectations from perturbative QCD. However, QCD predictions for the sum and the difference in rapidities of the two final-state objects show significant discrepancies with CMS data. In particular, next-to-leading-order QCD calculations, and two Monte Carlo event generators using different methods to merge matrix-element partons with evolved parton showers, appear inconsistent with the data as well as with each other.

Spires | arXiv:1111.5536 [hep-ex]

A measurement of the exclusive two-photon production of muon pairs in proton-proton collisions at at a centre-of-mass energy 7 TeV with the final state $p \mu^+ \mu^- p$, is reported using data corresponding to an integrated luminosity of 40 pb$^-1$ collected in 2010. The measured cross section is obtained with a fit to the dimuon $p_T$ distribution for muon pairs with invariant mass greater than 11.5 GeV with each muon $p_T > 4$ GeV and $|\eta| < 2.1$.

Different observables related to the two photons

Different observables related to the photon and extra jets.

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