NA60 results on thermal dimuons

Abstract

The NA60 experiment at the CERN SPS has measured muon pairs with unprecedented precision in 158A GeV In-In collisions. A strong excess of pairs above the known sources is observed in the whole mass region 0.2<M<2.6 GeV. The mass spectrum for M<1 GeV is consistent with a dominant contribution from pi+pi- -> rho -> mu+mu- annihilation. The associated rho spectral function shows a strong broadening, but essentially no shift in mass. For M>1 GeV, the excess is found to be prompt, not due to enhanced charm production, with pronounced differences to Drell-Yan pairs. The slope parameter Teff associated with the transverse momentum spectra rises with mass up to the rho, followed by a sudden decline above. The rise for M<1 GeV is consistent with radial flow of a hadronic emission source. The seeming absence of significant flow for M>1 GeV and its relation to parton-hadron duality is discussed in detail, suggesting a dominantly partonic emission source in this region. A comparison of the data to the present status of theoretical modeling is also contained. The accumulated empirical evidence, including also a Planck-like shape of the mass spectra at low pT and the lack of polarization, is consistent with a global interpretation of the excess dimuons as thermal radiation. We conclude with first results on omega in-medium effects.

10 pages, 12 figures, submitted to Eur. Phys. J. C

References in corpus (23)

• First Measurement of the rho Spectral Function in High-Energy Nuclear Collisions
• On the Manifestation of Chiral Symmetry in Nuclei and Dense Nuclear Matter
• Dilepton Radiation at the CERN Super Proton Synchrotron
• Comprehensive Interpretation of Thermal Dileptons at the SPS
• e+e--pair production in Pb-Au collisions at 158 GeV per nucleon
• Evidence for the production of thermal muon pairs with masses above 1 GeV/c^2 in 158A GeV Indium-Indium Collisions
• Modification of the rho meson detected by low-mass electron-positron pairs in central Pb-Au collisions at 158 A GeV/c
• Modification of the $\omega$-Meson Lifetime in Nuclear Matter
• Thermal Dilepton Radiation at Intermediate Masses at the CERN-SpS
• Evidence for radial flow of thermal dileptons in high-energy nuclear collisions
• Properties of $\rho$ and $\omega$ Mesons at Finite Temperature and Density as Inferred from Experiment
• NA60 results on the rho spectral function in In-In collisions
• Low Mass Dimuons Produced in Relativistic Nuclear Collisions
• Thermal Dimuon Yields at NA60
• Low mass dilepton production at ultrarelativistic energies
• Dimuon transverse momentum spectra as a tool to characterize the emission region in heavy-ion collisions
• First measurement of the rho spectral function in nuclear collisions
• Thermal dileptons at SPS energies
• Intermediate-mass dilepton spectra and the role of secondary hadronic processes in heavy-ion collisions
• Thermal Dilepton Production from Dropping rho based on the Vector Manifestation
• Lepton-pair production in nuclear collisions - past, present, future
• $\varphi$ Meson Production in In-In Collisions and the $\varphi$ Puzzle
• Thermal Dilepton Production from Dropping rho in the Vector Manifestation

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