The low mass dimuon spectra collected in p-U collisions by the NA38 experiment significantly exceeds the total cross section expected from previous analysis, done by other experiments. The 'excess' events have a harder p(T) distribution than the muon pairs from eta and omega Dalitz decays, expected to dominate the mass window 0.4-0.65 GeV/c(2). We conjecture that the excess events may be due to q (q) over bar annihilations, negligible at low p(T) but made visible by the m(T) cut applied in the NA38 data. Taking this assumption to parametrise the p-U spectra, we proceed with the corresponding analysis of the S-Cu, S-U and Pb-Pb data, collected by the NA38 and NA50 experiments, comparing the measured low mass dimuon spectra with the 'expected cocktail'.
Low mass dimuon production in proton and ion induced interactions at the SPS
Cicalo C;DE FALCO, ALESSANDRO;USAI, GIANLUCA;
2000-01-01
Abstract
The low mass dimuon spectra collected in p-U collisions by the NA38 experiment significantly exceeds the total cross section expected from previous analysis, done by other experiments. The 'excess' events have a harder p(T) distribution than the muon pairs from eta and omega Dalitz decays, expected to dominate the mass window 0.4-0.65 GeV/c(2). We conjecture that the excess events may be due to q (q) over bar annihilations, negligible at low p(T) but made visible by the m(T) cut applied in the NA38 data. Taking this assumption to parametrise the p-U spectra, we proceed with the corresponding analysis of the S-Cu, S-U and Pb-Pb data, collected by the NA38 and NA50 experiments, comparing the measured low mass dimuon spectra with the 'expected cocktail'.
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