QCD sum rule for pion in vacuum and dense medium

Investigation of the light pseudoscalar mesons (J^P=0^-) is one of the important research topics in order to better understand the perturbative and non-perturbative nature of Quantum Chromodynamics (QCD). We investigate the spectroscopic parameters of pion as a member of light meson family in a medium with finite density using QCD sum rules. The decay constant of pion linearly decreases with the increase in medium density and melts at higher values of the density ρ ≃ 1. 6 ρ_sat. At the saturation density, the in-medium mass of the pion is 198 MeV and the decay constant is 26 MeV. The results obtained in the current study may be also useful for future theoretical studies using different approaches and experimental studies, both in vacuum and in a dense medium.