[SEMINARI]: Dr. Oka: Flavor SU(3) Symmetry of the Pseudoscalar Meson-Baryon Couplings in QCD sum rules

[Arcadi Santamaria]

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                              S E M I N A R I

             [Image]   Departament de Física Teòrica    [Image]
                          Universitat de València
                       Institut de Física Corpuscular
                       Universitat de València - CSIC

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     Flavor SU(3) Symmetry of the Pseudoscalar Meson-Baryon Couplings in QCD
                                    sum rules.

                                 Makoto Oka

                       (Tokyo Institute of Technology)

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                              Seminari del IFIC
                 Tuesday 31 of October of 2000 at 12:30 PM
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                                    Resum

  It is important to study the meson-baryon couplings carefully as they are
  the key quantities that determine the meson exchange interactions between
 baryons. The SU(3) symmetry plays a central role there, but its foundation
      is not solid from QCD viewpoints. We have evaluated the diagonal
  meson-baryon couplings, $\pi NN$, $\eta NN$, $\pi \Xi\Xi$, $\eta \Xi\Xi$,
$\pi\Sigma \Sigma$ and $\eta \Sigma \Sigma$, using the QCD sum rules for the
    baryon-baryon correlation function with a meson, $i \int d^4x e^{iqx}
 \langle 0|{\rm T}[J_B(x) \bar J_B(0)] |M(p)\rangle$. We compare three Dirac
           structures: $i\gamma_5$, $i\gamma_5 \gamma\cdot p$, and
$\gamma_5\sigma_{\mu\nu}q^\mu p^\nu$ structures and have found that the last
one gives the most reliable predictions. We consider general combinations of
two independent baryon interpolating fields and study how the results depend
 on the interpolating fields. In the SU(3) limit, we identify the OPE terms
 responsible for the $F/D$ ratio, and find the ratio $F/D \sim 0.68$, which
  is surprisingly close to the value predicted by the SU(6) symmetry. SU(3)
breaking effects are partially taken into account to see their significance.

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