Interactions of 209-GeV muons within a magnetized-steel calorimeter have produced 1000±80 μ+μ- pairs from Jψ(3100) decay. Redundant systems of proportional and drift chambers maintained uniform acceptance and 9% mass resolution. Above 30 GeV, the cross section for ψ production by virtual photons is found to rise less steeply with energy than predicted by a quantum chromodynamics calculation. Its dependence on Q2 fits the vector-dominance form (1+Q2M2)-2 with M=2.7±0.5 GeV.
ASJC Scopus subject areas
- Physics and Astronomy(all)