Constraints on Nonrelativistic-QCD Long-Distance Matrix Elements from J/ψ Plus W/Z Production at the LHC.

Area of Science:

• High Energy Physics
• Quantum Chromodynamics
• Particle Physics

Background:

• Prompt J/ψ meson production in association with W or Z bosons is a key process for probing the dynamics of heavy quarkonium.
• Nonrelativistic QCD (NRQCD) factorization provides a theoretical framework to describe such processes, incorporating both perturbative and nonperturbative aspects.
• Long-distance matrix elements (LDMEs) are crucial nonperturbative parameters within NRQCD that govern quarkonium production.

Purpose of the Study:

• To investigate the associated production of prompt J/ψ mesons and W or Z bosons using the NRQCD factorization approach at next-to-leading order.
• To derive stringent constraints on charmonium LDMEs by comparing theoretical predictions with recent ATLAS measurements.
• To assess the validity of different LDME sets obtained from inclusive J/ψ production data.

Main Methods:

• Employing the NRQCD factorization approach at next-to-leading order in the strong coupling constant α_{s}.
• Considering intermediate color singlet (³S₁[¹], ³P<0xE1><0xB5><0xA3>[¹]) and color octet (¹S₀[⁸], ³S₁[⁸], ³P<0xE1><0xB5><0xA3>[⁸]) states.
• Comparing theoretical predictions with experimental data from the ATLAS collaboration.

Main Results:

• Most tested LDME sets show significant discrepancies with the ATLAS data, with predictions often falling short by factors of 3 to 10.
• Two LDME sets were found to violate cross-section positivity for direct J/ψ+W/Z production.
• The observed large rate of prompt J/ψ plus W production strongly favors the color octet mechanism within NRQCD.

Conclusions:

• The study provides stringent constraints on charmonium LDMEs, highlighting the importance of accurate nonperturbative input.
• The results underscore the crucial role of the color octet mechanism in prompt J/ψ production, particularly at the considered order of calculation.
• Further theoretical and experimental investigations are warranted to refine LDME determinations and understand quarkonium production dynamics comprehensively.