NA60 results on the $\rho$ spectral function in In-In collisions

S. Damjanovic , R. Arnaldi , R. Averbeck , K. Banicz , J. Castor (1) , B. Chaurand (2) , C. Cicalo , A. Colla , P. Cortese , A. David , A. de Falco , A. Devaux (1) , A. Drees , L. Ducroux (3) , H. Enyo , A. Ferretti , M. Floris , A. Forster , P. Force (1) , N. Guettet (1) , A. Guichard (3) , H. Gulkanian , J. Heuser , M. Keil , L. Kluberg (2) , C. Lourenco , J. Lozano , F. Manso (1) , A. Masoni , P. Martins , A. Neves , H. Ohnishi , C. Oppedisano , P. Parracho , Philippe Pillot (3) , G. Puddu , E. Radermacher , P. Ramalhete , P. Rosinsky , E. Scomparin , J. Seixas , S. Serci , R. Shahoyan , P. Sonderegger , H.J. Specht , R. Tieulent (3) , G. Usai , R. Veenhof , H.K. Wohri

1 LPC - Laboratoire de Physique Corpusculaire - Clermont-Ferrand
2 LLR - Laboratoire Leprince-Ringuet
3 IPNL - Institut de Physique Nucléaire de Lyon

The NA60 experiment at the CERN SPS has studied low-mass muon pairs in 158 AGeV In-In collisions. A strong excess of pairs is observed above the yield expected from neutral meson decays. After subtraction of the decay sources, the shape of the resulting mass spectrum is largely consistent with a dominant contribution from pi+pi- -> rho -> mu+mu- annihilation. The associated rho spectral function exhibits considerable broadening, but essentially no shift in mass. The acceptance-corrected pT spectra have a shape atypical for radial flow. They also significantly depend on mass, pointing to different sources in different mass regions. Both mass and pT spectra are compared to recent theoretical predictions.

Domaines: Physique Nucléaire Expérimentale [nucl-ex]

S. Damjanovic, R. Arnaldi, R. Averbeck, K. Banicz, J. Castor, et al.. NA60 results on the $\rho$ spectral function in In-In collisions. International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions (Hard Probes 2006), Jun 2006, Pacific Grove, United States. pp.327-334, ⟨10.1016/j.nuclphysa.2006.11.015⟩. ⟨in2p3-00126276⟩