Accessing gluon GTMD $F^g_{1,4}$ via the $\langle\sin(2ϕ)\rangle$ azimuthal asymmetry of exclusive $π^0$ production in $ep$ collisions

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Auteurs principaux: Tan, Chentao, Lu, Zhun
Format: Preprint
Publié: 2026
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author Tan, Chentao
Lu, Zhun
author_facet Tan, Chentao
Lu, Zhun
contents The longitudinal single-target spin asymmetry in exclusive $π^0$ production in $ep$ collisions is a sensitive probe of the imaginary part of the gluon generalized transverse momentum dependent distribution $F_{1,4}^g$. It appears as a characteristic $\sin(2ϕ)$ azimuthal correlation between the transverse momenta of the scattered electron and the recoil proton, generated by Coulomb-nuclear interference; consequently, the Primakoff process should be included. We compute the relevant gluon distributions in a light-front spectator model of the proton that explicitly incorporates gluonic degrees of freedom. This work presents the first model calculation of the imaginary part of $F_{1,4}^g$ and delivers predictions for the resulting asymmetries in kinematics relevant to the planned Electron-Ion Colliders (EIC and EicC), providing theoretical predictions for upcoming measurements.
format Preprint
id arxiv_https___arxiv_org_abs_2604_10738
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Accessing gluon GTMD $F^g_{1,4}$ via the $\langle\sin(2ϕ)\rangle$ azimuthal asymmetry of exclusive $π^0$ production in $ep$ collisions
Tan, Chentao
Lu, Zhun
High Energy Physics - Phenomenology
The longitudinal single-target spin asymmetry in exclusive $π^0$ production in $ep$ collisions is a sensitive probe of the imaginary part of the gluon generalized transverse momentum dependent distribution $F_{1,4}^g$. It appears as a characteristic $\sin(2ϕ)$ azimuthal correlation between the transverse momenta of the scattered electron and the recoil proton, generated by Coulomb-nuclear interference; consequently, the Primakoff process should be included. We compute the relevant gluon distributions in a light-front spectator model of the proton that explicitly incorporates gluonic degrees of freedom. This work presents the first model calculation of the imaginary part of $F_{1,4}^g$ and delivers predictions for the resulting asymmetries in kinematics relevant to the planned Electron-Ion Colliders (EIC and EicC), providing theoretical predictions for upcoming measurements.
title Accessing gluon GTMD $F^g_{1,4}$ via the $\langle\sin(2ϕ)\rangle$ azimuthal asymmetry of exclusive $π^0$ production in $ep$ collisions
topic High Energy Physics - Phenomenology
url https://arxiv.org/abs/2604.10738