QCD sum rules: Isospin symmetry breakings in pion-nucleon couplings
نویسندگان
چکیده
منابع مشابه
Isospin Splitting in the Pion-Nucleon Couplings from QCD Sum Rules
We use QCD sum rules for the three point function of a pseudoscalar and two nucleonic currents in order to estimate the charge dependence of the pion nucleon coupling constant gNNπ coming from isospin violation in the strong interaction. The effect can be attributed primarily to the difference of the quark condensates < ūu > and < d̄d >. Assuming that the π is a pure isostate we obtain for the s...
متن کاملIsospin Breaking in the Pion-Nucleon Coupling from QCD Sum Rules
We use QCD sum rules for the three point function of a pseudoscalar and two nucleonic currents in order to estimate the charge dependence of the pion nucleon coupling constant gNNπ coming from isospin violation in the strong interaction. The effect can be attributed primarily to the difference of the quark condensates < ūu > and < d̄d >. For the splitting (gppπ0−gnnπ0)/gNNπ we obtain an interval...
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We study isospin breaking instanton corrections to the operator product expansion of the nucleon correlation functions. After a comparison with quark model calculations based on the ’t Hooft interaction, we examine the role of instantons in the corresponding QCD sum rules. Instanton contributions are found to be absent in the chirally even sum rule, but significant in the chirallyodd one. They ...
متن کاملThe Pion-Nucleon Coupling Constant in QCD Sum Rules
The pion-nucleon coupling constant gπN is studied on the basis of the QCD sum rules. Both the Borel sum rules and the finite energy sum rules for gπN are used to examine the effects of higher dimensional operators (up to dim. 7) and αs corrections in the operator product expansion. Agreement with the experimental number is reached only when Sπ/SN is greater than one, where Sπ (SN ) is the conti...
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We calculate the coupling constants, gπNS11 and gηNS11 , using QCD sum rules in the presence of an external meson field. A covariant derivative is introduced within the S11 interpolating field so that in the nonrelativistic limit the field dominantly reduces to two quarks in the s-wave state and one quark in the p-wave state. Our result for the couplings obtained by further making use of the so...
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ژورنال
عنوان ژورنال: Physical Review C
سال: 1998
ISSN: 0556-2813,1089-490X
DOI: 10.1103/physrevc.57.61