Nuclear Physics Seminar

"First measurement of the rho spectral function in high-energy nuclear collisions"

Presented by Hans Specht, University of Heidelberg

Tuesday, March 21, 2006, 11:00 am — Small Seminar Room, Bldg. 510

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 yield expected from neutral meson decays. The unprecedented sample size of close to 400K events and the good mass resolution of about 2% allowed us to isolate the excess by subtraction of the decay sources. The shape of the resulting mass spectrum is
consistent with a dominant contribution from pi+ pi- --> rho --> pi+ pi- annihilation. The associated rho spectral function shows a strong broadening, but essentially no shift
in mass. The results are discussed in the frame of different
theoretical approaches addressing hadron properties close to the QCD phase boundary. They may rule out models linking hadron masses directly to the value of the chiral condensate.

Hosted by: Robert Pisarski

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