Isolated photon and photon+jet production at NNLO QCD accuracy

Chen, X.; Gehrmann, Thomas; Glover, E. W. N.; Hofer, M.; Huss, A.

doi:10.1007/jhep04(2020)166

Cited by 53 publications

(76 citation statements)

References 67 publications

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“…The prediction is systematically lower than the data by up to 20% at low E γ T but is closer to the data at higher E γ T , consistent with the results of such comparisons in pp collisions at LHC energies [9,10]. A recent calculation of isolated photon production at NNLO found that the predicted cross-sections were systematically larger at low E γ T than the NLO prediction [46], and thus may provide a better description of the data in this and previous measurements.…”

Section: Resultssupporting

confidence: 83%

Measurement of prompt photon production in sNN=8.16 TeV p + Pb collisions with ATLAS

Aaboud¹,

Aad²,

Abbott³

et al. 2019

Physics Letters B

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Measurement of prompt photon production in √ s NN = 8.16 TeV p+Pb collisions with ATLASThe ATLAS Collaboration The inclusive production rates of isolated, prompt photons in p+Pb collisions at √ s NN = 8.16 TeV are studied with the ATLAS detector at the Large Hadron Collider using a dataset with an integrated luminosity of 165 nb −1 recorded in 2016. The cross-section and nuclear modification factor R pPb are measured as a function of photon transverse energy from 20 GeV to 550 GeV and in three nucleon-nucleon centre-of-mass pseudorapidity regions, (−2.83, −2.02), (−1.84, 0.91), and (1.09, 1.90). The cross-section and R pPb values are compared with the results of a next-to-leading-order perturbative QCD calculation, with and without nuclear parton distribution function modifications, and with expectations based on a model of the energy loss of partons prior to the hard scattering. The data disfavour a large amount of energy loss and provide new constraints on the parton densities in nuclei.1 ATLAS uses a right-handed coordinate system with its origin at the nominal interaction point (IP) in the centre of the detector and the z-axis along the beam pipe. The x-axis points from the IP to the centre of the LHC ring, and the y-axis points upward. Cylindrical coordinates (r, φ) are used in the transverse plane, φ being the azimuthal angle around the z-axis. The pseudorapidity is defined in terms of the polar angle θ as η = − ln tan(θ/2) and the rapidity of the components of the beam, y, are defined in terms of their energy, E, and longitudinal momentum, p z , as y = 0.5 lncompartments. The first compartment is a copper/LAr electromagnetic calorimeter, while the remaining two tungsten/LAr calorimeter compartments collect the hadronic energy.During data-taking, events were initially selected using a level-1 trigger, implemented in custom electronics, based on energy deposition in the electromagnetic calorimeter. The high-level trigger [29] was then used to select events consistent with a high-E γ T photon candidate. The high level trigger was configured with five online E γ T thresholds from 15 GeV to 35 GeV. Each trigger is used for an exclusive region of the E γ T spectrum, starting 5 GeV above the trigger threshold because there the trigger is fully efficient. The highest-threshold trigger is used in the measurement over the whole E γ T range above 40 GeV and is unprescaled. The lower-threshold, prescaled, triggers are used to perform the measurement for E γ T in the range of 20 − 40 GeV.Data-taking was divided into two periods with different configurations of the LHC beams. In the first period, the lead ions circulated in beam 1 (clockwise) and protons circulated in beam 2, while in the second period the beams were reversed. These periods corresponded to integrated luminosities of 57 nb −1 and 108 nb −1 respectively. Photon reconstruction and identificationPhotons are reconstructed following a procedure used extensively in previous ATLAS measurements [10], of which only the main features are summarised here.Photon ca...

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Section: Resultssupporting

confidence: 83%

Measurement of prompt photon production in sNN=8.16 TeV p + Pb collisions with ATLAS

Aaboud¹,

Aad²,

Abbott³

et al. 2019

Physics Letters B

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“…The parameters are chosen to be as loose as possible to minimise a bias from the application of the photon isolation requirement at particle level. Since Frixione's criterion requires the upper limit on the transverse energy isolation to be exactly zero at r = 0, the criterion cannot be strictly looser than any non-zero photon isolation requirement at detector or particle level for all r < R. The photon isolation requirement is applied (see Table 1) using the procedure described in Section 6; the prescription employed is referred to as 'hybrid-cone isolation' [16,62] since it includes the application of the Frixione's criterion at a small value of ∆R (R = 0.1) and the fixed-cone isolation at ∆R = 0.4 used for the fiducial region of the measurement. Dynamic factorisation and renormalisation scales are adopted (E γ T ) as well as a dynamical merging scale withQ cut = 20 GeV [62].…”

Section: Theoretical Predictionsmentioning

confidence: 99%

“…Measurements of inclusive prompt-photon production also provide benchmarks to use in investigating novel approaches to parton radiation [12], next-to-leading-order (NLO) QCD corrections with matched parton showers [13], the relevance of threshold logarithms in QCD and electroweak corrections [14] and NNLO QCD corrections [15][16][17]. More specifically, the production of prompt photons, which is less sensitive to hadronisation effects than that of jets, can be used to pursue an alternative QCD description based on the k T factorisation approach combining off-shell amplitudes and transverse-momentum-dependent parton densities [12].…”

Section: Introductionmentioning

confidence: 99%

“…The prompt-photon measurements at the LHC are characterised by small uncertainties that demand precise theoretical predictions, e.g. those from NNLO QCD calculations [15][16][17], in order to fully exploit these data. Measurements involving isolated photons have also been used to constrain the contributions from new light scalar particles decaying into a photon pair [18].…”

Section: Introductionmentioning

confidence: 99%

“…The NLO QCD predictions of Jetphox [19,20] and Sherpa [21] based on several parameterisations of the PDFs are compared with the measurement. The NNLO QCD prediction of Nnlojet [16], which has significantly reduced uncertainties due to fewer missing higher-order terms, is also confronted with the data.…”

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confidence: 99%

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Measurement of the inclusive isolated-photon cross section in pp collisions at $$ \sqrt{s} $$ = 13 TeV using 36 fb−1 of ATLAS data

Aad

Abbott²,

Abbott³

et al. 2019

J. High Energ. Phys.

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Measurement of the inclusive isolated-photon cross section in pp collisions at √ s = 13 TeV using 36 fb −1 of ATLAS dataThe ATLAS CollaborationThe differential cross section for isolated-photon production in pp collisions is measured at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC using an integrated luminosity of 36.1 fb −1 . The differential cross section is presented as a function of the photon transverse energy in different regions of photon pseudorapidity. The differential cross section as a function of the absolute value of the photon pseudorapidity is also presented in different regions of photon transverse energy. Next-to-leading-order QCD calculations from Jetphox and Sherpa as well as next-to-next-to-leading-order QCD calculations from Nnlojet are compared with the measurement, using several parameterisations of the proton parton distribution functions. The predictions provide a good description of the data within the experimental and theoretical uncertainties. c 2019 CERN for the benefit of the ATLAS Collaboration. Reproduction of this article or parts of it is allowed as specified in the CC-BY-4.0 license. γ T > 125 GeV and |η γ | < 2.37, excluding the region 1.37 < |η γ | < 1.56. In addition, the double-differential cross section as a function of |η γ | in different regions of E γ T is also presented. The results are based on a data sample with a more than ten-fold increase in statistics relative to the previous study [5]. The measurement presented here is found to be consistent with the previous one in the overlapping kinematic regions. This increase in statistics allows improvements in the calibration of the photon energy and reductions in the experimental systematic uncertainties affecting the cross-section measurement, as well as an extension of the coverage in E γ T to higher values than previously measured. In this analysis, the region where the measurement is limited by systematic uncertainties is extended to E γ T ∼ 1 TeV, beyond what was achieved in the previous measurement. The NLO QCD predictions of Jetphox [19,20] and Sherpa [21] based on several parameterisations of the PDFs are compared with the measurement. The NNLO QCD prediction of Nnlojet [16], which has significantly reduced uncertainties due to fewer missing higher-order terms, is also confronted with the data. ATLAS detectorThe ATLAS detector [22][23][24] is a multipurpose detector with a forward-backward symmetric cylindrical geometry. It consists of an inner tracking detector surrounded by a thin superconducting solenoid, electromagnetic and hadronic calorimeters, and a muon spectrometer incorporating three large superconducting toroid magnets. The inner-detector system is immersed in a 2 T axial magnetic field and provides charged-particle tracking in the range |η| < 2.5. The high-granularity silicon pixel detector is closest to the interaction region and provides four measurements per track. The pixel detector is followed by the silicon microstrip tracker, which typically provides four three-dimension...

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Scale and isolation sensitivity of diphoton distributions at the LHC

Gehrmann

Glover

Huss

et al. 2021

J. High Energ. Phys.

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Precision measurements of diphoton distributions at the LHC display some tension with theory predictions, obtained at next-to-next-to-leading order (NNLO) in QCD. We revisit the theoretical uncertainties arising from the approximation of the experimental photon isolation by smooth-cone isolation, and from the choice of functional form for the renormalisation and factorisation scales. We find that the resulting variations are substantial overall, and enhanced in certain regions. We discuss the infrared sensitivity at the cone boundaries in cone-based isolation in related distributions. Finally, we compare predictions made with alternative choices of dynamical scale and isolation prescriptions to experimental data from ATLAS at 8 TeV, observing improved agreement. This contrasts with previous results, highlighting that scale choice and isolation prescription are potential sources of theoretical uncertainty that were previously underestimated.

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Isolated photon and photon+jet production at NNLO QCD accuracy

Cited by 53 publications

References 67 publications

Measurement of prompt photon production in sNN=8.16 TeV p + Pb collisions with ATLAS

Measurement of prompt photon production in sNN=8.16 TeV p + Pb collisions with ATLAS

Measurement of the inclusive isolated-photon cross section in pp collisions at $$ \sqrt{s} $$ = 13 TeV using 36 fb−1 of ATLAS data

Scale and isolation sensitivity of diphoton distributions at the LHC

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Isolated photon and photon+jet production at NNLO QCD accuracy

Cited by 53 publications

References 67 publications

Measurement of prompt photon production in sNN=8.16 TeV p + Pb collisions with ATLAS

Measurement of prompt photon production in sNN=8.16 TeV p + Pb collisions with ATLAS

Measurement of the inclusive isolated-photon cross section in pp collisions at $$ \sqrt{s} $$ = 13 TeV using 36 fb−1 of ATLAS data

Scale and isolation sensitivity of diphoton distributions at the LHC

Contact Info

Product

Resources

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Measurement of prompt photon production in sNN=8.16 TeV p + Pb collisions with ATLAS

Measurement of prompt photon production in sNN=8.16 TeV p + Pb collisions with ATLAS