J/psi and Upsilon Polarization in Hadronic Production Processes

Understand

Both charm and bottom quarks form nonrelativistic bound states analogous to positronium.

• The J/psi and psi(2S) charmonium states and the first three Upsilon(nS) bottomonium states, all spin-triplet S-wave quarkonium states below open-heavy-flavor thresholds, have relatively large branching ratios to e- e+ or mu- mu+ pairs.
• In hadron collisions, experiments measuring lepton pairs can determine polarization by using angular correlation techniques.
• The polarization, in turn, can be related theoretically to the production mechanism for the bound state.