Abstract
We calculate in the framework of collinear factorization the amplitude for the photoproduction of a near forward large mass diphoton at leading twist and next to leading order (NLO) in $\alpha_s$. We demonstrate the validity of factorization at this order, which was never achieved for such a reaction where the coefficient function describes a $2 \to 3$ hard process. While the Born order amplitude was purely imaginary and only probed the $x=\pm \xi$ cross-over line of generalized parton distributions (GPD) domain, the NLO result contains both a real and an imaginary part and probes the whole domain of definition of quark GPDs. The phenomenology of our results for medium (JLab) and higher energy (EIC) experiments will be developed in a future study.
Highlights
In our recent works [1,2] we studied at leading order (LO) in the QCD coupling constant αs the photoproduction of a large mass diphoton on a nucleon target γðq; εÞ þ Nðp1; s1Þ → γðq1; ε1Þ þ γðq2; ε2Þ þ N0ðp2; s2Þ; ð1Þ in the kinematical domain suitable to a factorization of generalized parton distributions (GPDs) and a hard amplitude
We calculate in the framework of collinear factorization the amplitude for the photoproduction of a near forward large mass diphoton at leading twist and next to leading order (NLO) in αs
In the kinematical domain suitable to a factorization of generalized parton distributions (GPDs) and a hard amplitude. This domain is defined by large diphoton invariant mass and center of mass energy and by a small momentum transfer squared t 1⁄4 ðp2 − p1Þ2 between the initial and final nucleons. This reaction, which superficially looks like timelike Compton scattering (TCS) [3–7] with the dilepton replaced by a diphoton, has a quite different structure since the hard amplitude describes a 2 → 3 process, contrarily to more familiar reactions—deeply virtual Compton scattering (DVCS), deeply virtual meson production (DVMP) or TCS—which involve a 2 → 2 process
Summary
In our recent works [1,2] we studied at leading order (LO) in the QCD coupling constant αs the photoproduction of a large mass diphoton on a nucleon target γðq; εÞ þ Nðp; s1Þ → γðq; ε1Þ þ γðq; ε2Þ þ N0ðp; s2Þ; ð1Þ in the kinematical domain suitable to a factorization of generalized parton distributions (GPDs) and a hard amplitude. This domain is defined by large diphoton invariant mass and center of mass energy and by a small momentum transfer squared t 1⁄4 ðp2 − p1Þ2 between the initial and final nucleons. Some of the results of this paper have been already presented in [13,14]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
