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First measurement of the rho spectral function in nuclear collisions

S. Damjanovic
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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 360 000 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.

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S. Damjanovic. 2005-10-13. First measurement of the rho spectral function in nuclear collisions. https://arxiv.org/abs/nucl-ex/0510044

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