[SEMINARI]: Dr. Andrianov: Extended quark models and QCD

[Arcadi Santamaria]

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                              S E M I N A R I

            [Image]    Departament de Física Teòrica     [Image]
                          Universitat de València
                      46100 Burjassot (València) Spain

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                          Extended quark models and QCD

                           Dr. Alexandr Andrianov

                         (Universitat de Barcelona)

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                     Aula de Seminaris de Física Teòrica
                    Thursday 07 of May of 1998 at 12:00
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                                    Resum

In the talk the low energy effective action of QCD below the chiral symmetry
 scale will be discussed, including operators of higher dimensions which can
be built from quark fields and their derivatives, without or with additional
 chiral fields. The quark effective action prepared in the QCD perturbation
 theory without explicit separation of chiral fields shares the features of
  the Nambu-Jona-Lasinio models being symmetric under chiral rotations but
possessing the strong coupling constants which induce the dynamical creation
   of constituent quark mass and pions. The corresponding effective meson
    lagrangian represents a generalization of the linear sigma-model. The
effective action which takes manifestly into account the dynamical formation
 of nearly massless pions (chiral fields) represents another way to describe
   the meson physics at low and intermediate energies. It starts from the
 chiral quark model and leads to a hybrid between the latter one and the NJL
  like model. In both cases the crucial role plays the matching to QCD with
the help of requirement of chiral symmetry restoration at energies above the
  CSB scale. Qualitatively, they bring a different CSB patterns: in the NJL
 approach the lightest scalar meson is a partner of the pion whereas in the
 Extended CQM the scalar meson becomes a partner of the heavy pion (pi-prime
 meson). Two approaches will be compared in the number of parameters derived
          from the meson phenomenology and in their predictivity.

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