Accessing the Pion 3D Structure at US and China Electron-Ion Colliders

Area of Science:

• High-energy physics
• Quantum chromodynamics
• Particle physics

Background:

• Generalized Parton Distributions (GPDs) are crucial for understanding the internal structure of hadrons.
• Pion GPDs are not well-constrained experimentally, limiting our knowledge of the pion's partonic structure.
• Electron-ion colliders offer a unique avenue to probe hadron structure through high-energy scattering.

Purpose of the Study:

• To conduct the first systematic feasibility study of accessing pion GPDs at an electron-ion collider.
• To investigate the role of quark-gluon interference in deep virtual Compton scattering (DVCS) off pions.
• To determine if beam-spin asymmetries can reveal the dominance of gluons in the pion's structure.

Main Methods:

• Utilizing state-of-the-art theoretical models for pion GPDs.
• Simulating deeply virtual Compton scattering (DVCS) processes at proposed electron-ion collider kinematics.
• Analyzing the impact of quark and gluon contributions on event rates and beam-spin asymmetries.

Main Results:

• Quark and gluon contributions interfere destructively, significantly modulating the expected event rate.
• The event rate is maximized when parton content originates from radiation off valence dressed quarks.
• Gluons induce a sign inversion in the beam-spin asymmetry across all models studied.

Conclusions:

• Accessing pion GPDs at electron-ion colliders via DVCS is feasible.
• The observed sign inversion in beam-spin asymmetry provides a clear experimental signature for gluon dominance.
• This research paves the way for a more comprehensive understanding of the pion's internal dynamics.