GLUONIC EFFECTS IN η- and η′-NUCLEON AND NUCLEUS INTERACTIONS
نویسنده
چکیده
Gluonic degrees of freedom play an important role in the physics of the flavour-singlet J = 1 channel [1] through the QCD axial anomaly [2]. The most famous example is the axial U(1) problem: the masses of the η and η′ mesons are much greater than the values they would have if these mesons were pure Goldstone bosons associated with spontaneously broken chiral symmetry [3]. This extra mass is induced by non-perturbative gluon dynamics [4–9]. Spontaneous chiral symmetry breaking is associated with a non-vanishing chiral condensate
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