Analysis of Spectral Modification of φ Mesons at Finite Density Using a Transport Approach in 12 GeV pA Reactions

Le résumé fourni par la source

Abstract The hadron spectrum at finite density is an important observable for exploring the origin of hadron masses. In the KEK-PS E325 experiment, the di-electron decays of $\phi$ mesons inside and outside nuclei were measured using $12 \,\mathrm{G}\mathrm{e\mathrm{V}}$ pA reactions. In the previous analysis, a significant excess was observed on the low-mass side of the $\phi$ meson peak in the data for slow-moving $\phi$ mesons ($\beta \gamma =p_{\phi }/m_{\phi }<1.25$) with the copper target, and in-medium vector meson spectral modification was verified. We used, for the first time, the PHSD transport approach to take into account the time evolution of the spatial density distribution of the target nuclei. Consistent with the previous analysis, a significant excess was observed in the present analysis as well. It was found that incorporating momentum dependence into the spectral modification leads to better agreement with the experimental results. For the slow-moving $\phi$ mesons with the copper target, the newly obtained modification parameters are consistent with those from the previous analysis within the uncertainties.

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