van Hees Hendrik, Rapp Ralf
Cyclotron Institute and Physics Department, Texas A & M University, College Station, Texas, 77843-3366 USA.
Phys Rev Lett. 2006 Sep 8;97(10):102301. doi: 10.1103/PhysRevLett.97.102301.
Employing thermal dilepton rates based on a medium-modified electromagnetic correlation function we show that recent dimuon spectra of the NA60 Collaboration in central In-In collisions at the CERN-SPS can be understood in terms of radiation from a hot and dense hadronic medium. Earlier calculated in-medium rho-meson spectral functions provide an accurate description of the data up to dimuon invariant masses of about M approximately or equal to 0.9 GeV, with good sensitivity to the predicted rho-meson line shape, identifying baryon-induced modifications as the prevalent ones. A reliable evaluation of the contribution enables the study of further medium effects: at masses M>0.9 GeV, 4-pion type annihilation accounts for the experimentally observed excess (possibly augmented by effects of "chiral mixing"), while predictions for thermal emission from in-medium omega and phi mesons may be tested in the future.
利用基于介质修正电磁关联函数的热双轻子速率，我们表明欧洲核子研究组织超级质子同步加速器（CERN-SPS）上铟-铟中心碰撞中NA60合作组最近的双μ子谱，可以用来自热密强子介质的辐射来解释。早期计算的介质中ρ介子谱函数对数据提供了准确描述，直到双μ子不变质量约为M≈0.9 GeV，对预测的ρ介子线形具有良好的敏感性，确定重子诱导的修正为主要修正。对该贡献的可靠评估使得能够研究进一步的介质效应：在质量M>0.9 GeV时，4π型湮灭解释了实验观测到的过量（可能因“手征混合”效应而增强），而介质中ω和φ介子热发射的预测未来可能会得到检验。
