Photon-initiated processes at high mass

Harland–Lang, Lucian; Хозе, В. А.; Ryskin, M.G.

doi:10.1103/physrevd.94.074008

Cited by 48 publications

(53 citation statements)

References 28 publications

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“…In Fig. 1, the photon PDF, xγ(x, Q 2 ), is shown at the evolved scale Q 2 = 10 4 GeV 2 , and it is compared to the predictions obtained using HKR16 [12], LUXqed [13,14] and NNPDF3.0QED [15]. The xFitter_epHMDY fit is shown with the associated experimental PDF uncertainties at the 68% confidence level (CL), obtained using the MC replica method.…”

Section: Resultsmentioning

confidence: 99%

The photon PDF determination within the xFitter framework

Giuli¹,

team²

2017

Proceedings of the European Physical Society Conference on High Energy Physics — PoS(EPS-HEP2017)

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The xFitter project (former HERAFitter project) is an open-source package that provides a framework for the determination of the parton distribution functions (PDFs) of the proton for many different kinds of analyses in Quantum Chromodynamics (QCD). xFitter version 2.0.0 has recently been released, and offers an expanded set of tools and options. It incorporates experimental data from a wide range of experiments including fixed-target, Tevatron, HERA, and LHC. xFitter can analyze this data up to next-to-next-to-leading-order (NNLO) in perturbation theory with a variety of theoretical calculations including numerous methodological options for carrying out PDF fits and plotting tools which help visualise the results. In this contribution, a determination of the photon PDF from fits to recent ATLAS measurements of high-mass Drell-Yan dilepton production at √ s = 8 TeV using this framework is presented.

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Section: Resultsmentioning

confidence: 99%

The photon PDF determination within the xFitter framework

Giuli¹,

team²

2017

Proceedings of the European Physical Society Conference on High Energy Physics — PoS(EPS-HEP2017)

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“…where the second approximate equality is true in the Q 2 M 2 limit and the transverse projection is as defined in (6). This allows us to write…”

Section: Test Case: Lepton/photon-hadron Scatteringmentioning

confidence: 99%

The proton in high definition: revisiting photon-initiated production in high energy collisions

Harland–Lang¹

2020

J. High Energ. Phys.

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We re-examine the current state of the art for the calculation of photon-initiated processes at the LHC, as formulated in terms of a photon PDF in the proton that may be determined rather precisely from the known proton structure functions. We in particular demonstrate that a by construction more precise calculation is provided by a direct application of the structure function approach, best known from the case of Higgs Boson production via vector boson fusion. This avoids any artificial scale variation uncertainties, which can otherwise be rather significant for processes calculated within the standard approach thus far. To understand the source of these, we present a detailed comparison of the structure function approach and its relation to the photon PDF. We then provide precise predictions for the photon-initiated contribution to lepton pair production at the LHC, including the lepton pair transverse momentum distribution. Thus, by a direct application of the structure function formalism we show how the contribution from initial-state photons at the LHC may for the first time be included with high precision in a universal and straightforward way, providing a high definition picture of the photon content of the proton.

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“…In Fig. 1, the photon PDF, xγ(x, Q 2 ), is shown at Q 2 = 10 4 GeV 2 , and it is compared to the corresponding NNPDF3.0QED [16], LUXqed [17] and HKR16 [18] results. In the left plot, the comparison is shown in an absolute scale, while the plot on right shows the ratio of different results normalized to the central value of the fit.…”

Section: Pos(dis2017)196mentioning

confidence: 99%