Low mass dimuon production in proton and ion induced interactions at the SPS

• Published in: The European physical journal. C, Particles and fields Particles and fields, 2000-03, Vol.13 (1), p.69-78
• Main Author: Abreu et al, M.C.
• Format: Article
• Language: English
• Subjects: High Energy Physics - Phenomenology; Physics; Spectra
• ISSN: 1434-6044; 1434-6052
• DOI: 10.1007/s100520000288

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 \(p_{\mathrm{T}}\) 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 \(q\bar{q}\) annihilations, negligible at low \(p_{\mathrm{T}}\) but made visible by the \(m_{\mathrm{T}}\) 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’.