Evidence for Radial Flow of Thermal Dileptons in High-Energy Nuclear Collisions

Journal Article · Fri Jan 18 04:00:00 EST 2008 · Physical Review Letters

DOI:https://doi.org/10.1103/PHYSREVLETT.100.022302· OSTI ID:21020935

Arnaldi, R; Colla, A; Cortese, P; Ferretti, A; Oppedisano, C; Scomparin, E ^[1]; Banicz, K; Damjanovic, S ^[2]; Castor, J; Devaux, A; Fargeix, J; Force, P; Manso, F ^[3]; Chaurand, B ^[4]; Cicalo, C; Falco, A de; Floris, M; Masoni, A; Puddu, G; Serci, S ^[5]

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1. Universita di Torino and INFN, Turin (Italy)
2. CERN, 1211 Geneva 23 (Switzerland)
3. LPC, Universite Blaise Pascal and CNRS-IN2P3, Clermont-Ferrand (France)
4. LLR, Ecole Polytechnique and CNRS-IN2P3, Palaiseau (France)
5. Universita di Cagliari and INFN, Cagliari (Italy)

The NA60 experiment at the CERN SPS has studied low-mass dimuon production in 158A GeV In-In collisions. An excess of pairs above the known meson decays has been reported before. We now present precision results on the associated transverse momentum spectra. The slope parameter T{sub eff} extracted from the spectra rises with dimuon mass up to the {rho}, followed by a sudden decline above. While the initial rise is consistent with the expectations for radial flow of a hadronic decay source, the decline signals a transition to an emission source with much smaller flow. This may well represent the first direct evidence for thermal radiation of partonic origin in nuclear collisions.

• OSTI ID: 21020935
• Journal Information: Physical Review Letters, Journal Name: Physical Review Letters Journal Issue: 2 Vol. 100; ISSN 0031-9007; ISSN PRLTAO
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
CERN SPS SYNCHROTRON
COLLIDING BEAMS
GEV RANGE 100-1000
HADRONIC PARTICLE DECAY
INDIUM 115 TARGET
MESONS
SPECTRA
TRANSVERSE MOMENTUM