The NA60 experiment has studied low-mass muon pairs in 158 AGeV Indium-Indium collisions at the CERN SPS. A strong excess of pairs is observed above the expectation from neutral meson decays. The unprecedented sample size of 360000 events and the good mass resolution of about 2% allow to isolate the excess by subtraction of the known sources. The shape of the resulting mass spectrum 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.

First measurement of the ρ spectral function in nuclear collisions

FERRETTI, Alessandro;
2006

Abstract

The NA60 experiment has studied low-mass muon pairs in 158 AGeV Indium-Indium collisions at the CERN SPS. A strong excess of pairs is observed above the expectation from neutral meson decays. The unprecedented sample size of 360000 events and the good mass resolution of about 2% allow to isolate the excess by subtraction of the known sources. The shape of the resulting mass spectrum 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.
18th International Conference on Ultrarelativistic Nucleus-Nucleus Collisions: Quark Matter 2005 (QM 2005)
Budapest, Hungary
4-9 Aug 2005
774
715
718
R Arnaldi; R Averbeck; K Banicz; J Castor; B Chaurand; C Cicalò; A Colla; P Cortese; S Damjanovic; A David; A De Falco; A Devaux; A Drees; L Ducroux; H En'yo; J Fargeix; A Ferretti; M Floris; A Förster; P Force; N Guettet; A Guichard; H Gulkanian; J M Heuser; M Keil; L Kluberg; C Lourenço; J Lozano; F Manso; A Masoni; P Martins; A Neves; H Ohnishi; C Oppedisano; P Parracho; Ph Pillot; G Puddu; E Radermacher; P Ramalhete; P Rosinsky; E Scomparin; J Seixas; S Serci; R Shahoyan; P Sonderegger; H J Specht; R Tieulent; G Usai; R Veenhof; H K Wöhri
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2318/51809
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