Geometric scaling in inclusive charm production

Area of Science:

• High-energy particle physics
• Quantum chromodynamics
• Collider physics

Background:

• Inclusive charm production is a key process for understanding proton structure at high energies.
• Geometric scaling has been observed in deep inelastic scattering, but its application to heavy-quark production requires further investigation.
• Proton structure functions at small Bjorken-x probe the high-density regime of quantum chromodynamics.

Purpose of the Study:

• To investigate the phenomenon of geometric scaling in inclusive charm production.
• To determine the role of saturation and color transparency in charm production at the HERA collider.
• To test the validity of saturation models in describing experimental data.

Main Methods:

• Analysis of inclusive charm production cross-section data from the HERA collider.
• Application of two saturation models capable of describing proton structure function data at small Bjorken-x.
• Examination of geometric scaling in terms of photon virtuality and saturation momentum.

Main Results:

• Inclusive charm production exhibits geometric scaling over a broad range of photon virtualities.
• The saturation momentum (Q(2)(sat)(x)) remains below the hard scale (μ(2)(c)=4m(2)(c)) in the HERA kinematic domain.
• Charm production primarily probes the color transparency regime, with negligible unitarization effects.
• Observed scaling on τ = Q(2)/Q(2)(sat)(x) above the saturation limit.

Conclusions:

• Geometric scaling is a robust feature of inclusive charm production.
• The findings support the dominance of the color transparency regime in this process.
• The studied saturation models successfully describe HERA data and predict the observed scaling behavior.