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

Harland–Lang, Lucian

doi:10.1007/jhep03(2020)128

Cited by 11 publications

(8 citation statements)

References 42 publications

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“…A key ingredient in this is the availability of high precision theoretical predictions for the SM processes, an important element of which is the contribution from photon-initiated (PI) channel. A rather useful method 1,2 to provide this is to work in the 'structure function' (SF) framework. Here, one calculates the cross section directly in terms of the proton structure functions.…”

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confidence: 99%

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Physics with leptons and photons at the LHC

Harland–Lang¹

2021

Phys. Rev. D

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LHC collisions can act as a source of photons in the initial state. This mechanism plays an important role in the production of particles with electroweak couplings, and a precise account of photon-initiated (PI) production at the LHC is a key ingredient in the LHC precision physics programme. I will discuss the possibility of modelling PI processes directly via the structure function approach. This can provide percent level precision in the production cross sections, and is therefore well positioned to account for LHC precision requirements. This formalism in addition allows one to make use of another useful feature of photons, namely that they are colour-singlet and can often be emitted elastically (or quasi-elastically) from the proton. I will discuss recent work on applications of the structure function approach to precision calculations of PI production in the inclusive mode, and to 'exclusive' processes with rapidity gaps, which can provide a unique probe of the Standard Model and physics beyond it.

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confidence: 99%

“…M µν corresponds to the γγ → X(k) production amplitude, with arbitrary photon virtualities. ρ is the density matrix of the virtual photon, which is given in terms of the well known proton structure functions, see 1,2 for an explicit expression and 2 for the extension to include initial-state Z bosons.…”

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confidence: 99%

Physics with leptons and photons at the LHC

Harland–Lang¹

2021

Phys. Rev. D

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“…The SF framework is a rather useful method [3,4] for calculating the PI lepton pair production cross section directly in terms of the proton structure functions. For processes such as (off Zpeak) lepton pair production this provides percent precision in the predicted cross sections, with no accompanying factorization scale variation uncertainty, as is present in the calculation within collinear factorization.…”

Section: The Structure Function Approach and Inclusive Photon-initiat...mentioning

confidence: 99%

Physics from Photons at the LHC

Harland–Lang

2022

SciPost Phys. Proc.

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LHC collisions can act as a source of photons in the initial state. This mechanism plays an important role in the production of particles with electroweak couplings, and a precise account of photon-initiated (PI) production at the LHC is a key ingredient in the LHC precision physics programme. I will discuss the possibility of modelling PI processes directly via the structure function approach. This can provide percent level precision in the production cross sections, and is therefore well positioned to account for LHC precision requirements. This formalism in addition allows one to make use of another useful feature of photons, namely that they are colour-singlet and can often be emitted elastically (or quasi-elastically) from the proton. I will discuss recent work on applications of the structure function approach to precision calculations of PI production in the inclusive mode, and to `exclusive' processes with rapidity gaps, which can provide a unique probe of the Standard Model and physics beyond it.

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“…Aside from its use for the computation of photon and lepton PDFs, the method has also been used in refs. [13,19] in an LHC context. The formulae reported in these latter references, however, differ from our eq.…”

Section: The Nlo Powheg Calculationmentioning

confidence: 99%

“…For example, eq. (2.1) of [19] is given in terms of a density matrix of the virtual photon, eq. (2.2), that is a well defined object, but does not enter the calculation of the cross section, since the Mi depend upon xBj and the Mi enter in the energies Ei in (2.1).…”

Section: The Nlo Powheg Calculationmentioning

confidence: 99%

Photon and leptons induced processes at the LHC

Buonocore

Nason

Tramontano

et al. 2021

J. High Energ. Phys.

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We study a few basic photon- and lepton-initiated processes at the LHC which can be computed using the recently developed photon and lepton parton densities. First, we consider the production of a massive scalar particle initiated by lepton-antilepton annihilation and photon-photon fusion as representative examples of searches of exotic particles. Then we study lepton-lepton scattering, since this Standard-Model process may be observable at the LHC. We examine these processes at leading and next-to-leading order and, using the POWHEG method, we match our calculations to parton shower programs that implement the required lepton or photon initial-states. We assess the typical size of cross-sections and their uncertainties and discuss the preferred choices for the factorization scale. These processes can also be computed starting directly from the lepto-production hadronic tensor, leading to a result where some collinear-enhanced QED corrections are missing, but all strong corrections are included. Thus, we are in the unique position to perform a comparison of results obtained via the factorization approach to a calculation that does not have strong corrections. This is particularly relevant in the case of lepton-scattering, that is more abundant at lower energies where it is affected by larger strong corrections. We thus compute this process also with the hadronic-tensor method, and compare the results with those obtained with POWHEG. Finally, for some lepton-lepton scattering processes, we compare the size of the signal to the main quark-induced background, which is double Drell-Yan production, and outline a preliminary search strategy to enhance the signal to background ratio.

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

Cited by 11 publications

References 42 publications

Physics with leptons and photons at the LHC

Physics with leptons and photons at the LHC

Physics from Photons at the LHC

Photon and leptons induced processes at the LHC

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