Heavy quarkonium production and polarization

Area of Science:

• High Energy Physics
• Quantum Chromodynamics (QCD)
• Particle Physics

Background:

• Heavy quarkonium production at large transverse momentum (pT) is crucial for understanding fundamental interactions.
• Existing theoretical models often struggle to fully explain experimental observations, particularly the large enhancement in cross sections.

Purpose of the Study:

• To develop a comprehensive perturbative QCD factorization formalism for heavy quarkonium production.
• To incorporate both leading-power (LP) and next-to-leading-power (NLP) contributions in the theoretical framework.
• To investigate the role of nonrelativistic QCD (NRQCD) in describing fragmentation functions and polarization phenomena.

Main Methods:

• Developed a perturbative QCD factorization formalism.
• Included LP and NLP contributions in the m(Q)^2/pT^2 expansion.
• Estimated fragmentation functions using the NRQCD formalism.
• Analyzed heavy quarkonia polarization in NLP channels.

Main Results:

• The proposed formalism successfully incorporates both LP and NLP contributions.
• Fragmentation function estimates using NRQCD reproduce the large enhancement observed in previous calculations.
• Heavy quarkonia produced via NLP channels exhibit a preference for longitudinal polarization.

Conclusions:

• The developed QCD factorization approach provides a more complete description of heavy quarkonium production.
• NRQCD fragmentation functions are essential for understanding the observed enhancements.
• NLP production channels offer insights into heavy quarkonia polarization.