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Register a new userScalar susceptibility from the instanton vacuum with meson-loop corrections
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Seung-il Nam
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The scalar susceptibility (chi_s) of QCD, which represents the response of the chiral condensate to a small perturbation of explicit chiral-symmetry breaking, is investigated within the nonlocal chiral quark model (NLchiQM) based on the instanton vacuum configuration for N_f = 2. We also take into account 1/N_c meson-loop (ML) corrections including scalar and pseudoscalar mesons. It turns out that the chiral condensate is modified to a large extend by the ML corrections in the vicinity of m = 0, whereas its effect becomes weak beyond m ~ 100 MeV. As numerical results, we find that chi_s = -0.34 GeV^2 with the ML corrections and 0.18 GeV^2 without it, respectively. From these observations, we conclude that the ML corrections play an important role in the presence of finite current-quark mass.
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