QCD anatomy of photon isolation

Becher, Thomas; Favrod, Samuel; Xu, Xiaofeng (2023). QCD anatomy of photon isolation. Journal of High Energy Physics, 2023(1) Springer 10.1007/JHEP01(2023)005

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To separate the energetic photons produced in hard scattering processes from those from other sources, measurements impose isolation requirements which restrict the hadronic radiation inside a cone around the photon. In this paper, we perform a detailed factorization analysis of the QCD effects associated with photon isolation. We show that for small cone radius R, photon isolation effects can be captured by a fragmentation function describing the decay of a parton into a photon accompanied by hadronic radiation. We compute this fragmentation function for different isolation criteria and solve the associated renormalization group equations to resum logarithms of R. For small isolation energy, the cone fragmentation function factorizes further, into collinear functions describing energetic quarks and gluons near the cone boundary and functions encoding their soft radiation emitted into the cone. Based on this factorization we also resum the non-global logarithms of the ratio of the photon energy and the isolation energy, so that we control all logarithmically enhanced terms in the cross section. In this limit, we provide a simple formula to convert NNLO cross section results from smooth-cone isolation to fixed-cone isolation.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Theoretical Physics
10 Strategic Research Centers > Albert Einstein Center for Fundamental Physics (AEC)

UniBE Contributor:

Becher, Thomas, Favrod, Samuel Clément, Xu, Xiaofeng

Subjects:

500 Science > 530 Physics
000 Computer science, knowledge & systems

ISSN:

1029-8479

Publisher:

Springer

Language:

English

Submitter:

Binia Marti

Date Deposited:

17 Mar 2023 15:18

Last Modified:

17 Mar 2023 23:27

Publisher DOI:

10.1007/JHEP01(2023)005

BORIS DOI:

10.48350/179870

URI:

https://boris.unibe.ch/id/eprint/179870

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