Extraction of Precise Gamow-Teller Quenching Value Q, Landau-Migdal Parameter g'{{NΔ }} and Pion Condensation

Measurements on ⁹⁰Zr(p, n) and ⁹⁰Zr(n, p) reactions at 300 MeV were made and reliable S_β- and S_β+ values are successfully extracted. A Gamow-Teller quenching factor (Q) in terms of the spin sum rule of S_β- - S_β+ = 3(N - Z) is derived as Q = 0.89 ± 0.04(MDA) ± 0.04(IVSM) apart from the systematic uncertainty of Δ / σ _GT <= 15% . The Landau-Migdal (LM) parameters representing a short-range correlation in an isospin-spin channel are deduced to be g'_{NN} = 0.60 ± 0.02 and g'_{NΔ } = 0.24 ± 0.10 with the Chew-Low coupling constant f_Δ/fπ = 2. The critical density of the pion condensation is estimated to be ρ_c 2_ρ0 which can be easily realized in the neutron stars. Recent observation of the surface temperature of the neutron star 3C58 supports the pionic cooling mechanism and consequently manifestation of the pion condensation in neutron stars.