Evidence for Simultaneous Production of J/ψ and ϒ Mesons.

Area of Science:

• High-energy particle physics
• Quantum chromodynamics
• Hadron collider physics

Background:

• The simultaneous production of heavy quarkonium states provides a unique probe of the strong nuclear force.
• Understanding the production mechanisms of J/ψ and ϒ mesons is crucial for testing quantum chromodynamics (QCD) predictions.

Purpose of the Study:

• To report the first evidence of simultaneous J/ψ and ϒ meson production.
• To measure the effective cross-section characterizing the initial parton spatial distribution in proton-antiproton collisions.

Main Methods:

• Analysis of 8.1 fb⁻¹ of data collected by the D0 experiment at the Fermilab Tevatron Collider.
• Utilizing proton-antiproton collisions at a center-of-mass energy of 1.96 TeV.
• Identifying events with both J/ψ and ϒ mesons to isolate specific production channels.

Main Results:

• Evidence for the simultaneous production of J/ψ and ϒ mesons was observed.
• The effective cross-section for initial parton spatial distribution was determined to be σ_eff = 2.2 ± 0.7(stat) ± 0.9(syst) mb.
• The observed production characteristics are consistent with dominant gluon-gluon interactions.

Conclusions:

• The simultaneous production of J/ψ and ϒ mesons is a rare but measurable phenomenon.
• The extracted effective cross-section offers insights into the spatial distribution of partons within hadrons.
• This measurement provides a valuable benchmark for theoretical models of heavy quarkonium production in high-energy collisions.