Chiral Restoration in a Nuclear Medium : Probed by S-Wave Pion Dynamics(Hadron properties and chiral symmetry in medium, Chiral dynamics in nuclear medium, New Frontiers in QCD-Exotic Hadrons and Hadronic Matter-)

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概要

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• Using 500MeV (d, ^3Heπ^-) pion transfer reactions in recoil free kinematics, pionic 1s-states were populated in the ^<115, 119, 123>Sn isotopes and their binding energies and widths determined by precision missing mass spectroscopy. Using these data and corresponding ones from iso-scalar light nuclei nuclei, ^<16>O, ^<20>Ne and ^<28>Si, we determined the pion nucleus s-wave strength parameters, b_0, b_1, ReB_0, and ImB_0. By comparison of the iso-vector pion nucleon strength, determined from pionic hydrogen X-ray spectroscopy b^<free>_1, with the b_1 in a nuclear medium scaled to the density ρ(0), we deduced a scaling factor, the square of the pion decay constant in the vacuum and in nuclear medium, as R=b^<free>_1/b_1=f^2_π(ρ_0)/f^2_π=0.64. Thus from the observed increase of the pion s-wave iso-vector strength in a nuclear medium a reduction of f^2_π, the order parameter of chiral symmetry breaking, is indicated in accordance with theoretical expectations. This finding is supported by recent π^+ and π^- scattering experiments. A short outlook is given on a future program at RIBF in RIKEN for precision studies of deeply bound 1s-states in heavy nuclei.

• 2007-11-09

著者

• Kienle Paul

  Stefan Meyer Institute Of The Austrian Academy Of Sciences:technische Universitat Munchen

関連論文

• Chiral Restoration in a Nuclear Medium : Probed by S-Wave Pion Dynamics(Hadron properties and chiral symmetry in medium, Chiral dynamics in nuclear medium, New Frontiers in QCD-Exotic Hadrons and Hadronic Matter-)

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