arXiv subjects

Masaharu Tanabashi

Publications and source records attributed to Masaharu Tanabashi.

40 records · Page 3Linked to original sources

arXiv1995

Formulations of spin 1 resonances in the chiral lagrangian

Equivalence of the hidden local symmetry formulation with non-minimal interactions and the anti-symmetric tensor field method of $ρ$ and $a_1$ mesons in the chiral lagrangian is shown by using the auxiliary field method. Violation of the KSRF I relation, which becomes important in the application of chiral lagrangian to {\em non QCD-like} technicolor models can be parametrized by non-minimal coupling in the hidden local symmetry formalism keeping low energy theorem of hidden local symmetry. We also obtain explicit correspondence of parameters in both formulations.

hep-ph↗

arXiv1993

Phase Structure of the Gauged Yukawa Model

Based on the ladder Schwinger-Dyson equation, we investigate phase struc- ture of the gauged Yukawa model possessing a global $SU(2)_L \times SU(2)_R$ symmetry and an unbroken (vector-like) gauge symmetry. We show that even when we tune the squared mass of the scalar boson in the Lagrangian to be positive, there still exists the dynamical chiral symmetry breaking due to fermion pair condensate (VEV of the composite scalar) triggered by the strong Yukawa coupling larger than a certain critical value. We find a "nontrivial ultraviolet fixed line" and "renormalized trajectories" in the three-dimensional coupling space of the Yukawa coupling, the gauge cou- pling and the "hopping parameter" of the elementary scalar field. Presence of the gauge coupling is crucial to existence of the fixed line. Implications of the result for the lattice calculation and the top quark condensate model are also discussed.

hep-ph↗

arXiv1993

Chiral Perturbation to One Loop Including the $ρ$ Meson

We formulate the chiral perturbation theory at the one loop level in the effective lagrangian including the $ρ$ meson as a dynamical gauge boson of a hidden local symmetry(HLS). The size of radiative correction to the phenomenological parameter $a$ of HLS is estimated to be about $10$\%. The complete list of ${\cal O}(E^4)$ terms is given and the one loop counter terms are determined explicitly in the $N$ flavor model. We also obtain matching conditions to the conventional chiral perturbation of Gasser and Leutwyler in the chiral limit in a renormalization scale independent manner. We find that Gasser--Leutwyler's estimates for $L_{9,10}$ are saturated by $ρ$ and its one loop contributions without introducing non-minimal couplings of $π$-$ρ$ system, suggesting the absence of the tree level $a_1$ meson contributions.

hep-ph↗

arXiv1992

Renormalization in the Gauged Nambu--Jona-Lasinio Model

Based on the Cornwall-Jackiw-Tomboulis effective potential, we extensively study nonperturbative renormalization of the gauged Nambu-Jona-Lasinio model in the ladder approximation with standing gauge coupling. Although the pure Nambu-Jona-Lasinio model is not renormalizable, presence of the gauge interaction makes it possible that the theory is renormalized as an interacting continuum theory at the critical line in the ladder approximation. Extra higher dimensional operators (``counter terms'') are not needed for the theory to be renormalized. By virtue of the effective potential approach, the renormalization (``symmetric renormalization'') is performed in a phase-independent manner both for the symmetric and the spontaneously broken phases of the chiral symmetry. We explicitly obtain $β$ function having a nontrivial ultraviolet fixed line for the renormalized coupling as well as the bare one. In both phases the anomalous dimension is very large ($ \ge 1$) without discontinuity across the fixed line. Operator product expansion is explicitly constructed, which is consistent with the large anomalous dimension owing to the appearance of the nontrivial extra power behavior in the Wilson coefficient for the unit operator. The symmetric renormalization breaks down at the critical gauge coupling, which is cured by the generalized renormalization scheme (``$\tM$-dependent renormalization''). Also emphasized is the formal resemblance to the four-fermion theory in less than four dimensions which is renormalizable in $1/N$ expansion.

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