arXiv subjects

M. Takizawa

Publications and source records attributed to M. Takizawa.

42 records · Page 3Linked to original sources

arXiv1998

Finite Quark Mass Effects in the Improved Ladder Bethe-Salpeter Amplitudes

We study the finite quark mass effects of the low-energy QCD using the improved ladder Schwinger-Dyson and Bethe-Salpeter equations which are derived in the manner consistent with the vector and axial-vector Ward-Takahashi identities. The non-perturbative mass-independent renormalization allows us to calculate the quark condensate for a non-zero quark mass. We explicitly show that the PCAC relation holds. The key ingredients are the Cornwall-Jackiw-Tomboulis effective action, the generalized Noether current and the introduction of the regularization function to the Lagrangian. The reasonable values of the pion mass, the pion decay constant and the quark condensate are obtained with a rather large $Λ_{QCD}$. The pion mass square and the pion decay constant are almost proportional to the current quark mass up to the strange quark mass region. It suggests that the chiral perturbation is applicable up to the strange quark mass region. We study the validity of the approximation often used in solving the Bethe-Salpeter equations too.

hep-ph↗

arXiv1996

Strong $U_A(1)$ breaking in radiative $η$ decays

We study the \egg, \egm and \epg decays using an extended three-flavor Nambu-Jona-Lasinio model that includes the 't~Hooft instanton induced interaction. We find that the $η$-meson mass, the \egg, \egm and \epg decay widths are in good agreement with the experimental values when the $U_{A}(1)$ breaking is strong and the flavor $SU(3)$ singlet-octet mixing angle $θ$ is about zero. The calculated $ηγγ^\ast$ transition form factor has somewhat weaker dependence on the squared four-momentum of the virtual photon. The effects of the $U_A(1)$ anomaly on the scalar quark contents in the nucleon, the $Σ_{πN}$ and $Σ_{KN}$ terms and the baryon number one and two systems are also studied.

hep-ph↗

arXiv1996

$η$-Meson Decays and Strong $U_A(1)$ Breaking in the Three-Flavor Nambu-Jona-Lasinio Model

We study the $η\to γγ$ and $η\to π^0 γγ$ decays using an extended three-flavor Nambu-Jona-Lasinio model that includes the 't~Hooft instanton induced interaction. We find that the $η$-meson mass, the $η\to γγ$ decay width and the $η\to π^0 γγ$ decay width are in good agreement with the experimental values when the $U_{A}(1)$ breaking is strong and the flavor $SU(3)$ singlet-octet mixing angle $θ$ is about zero. The effects of the $U_A(1)$ breaking on the baryon number one and two systems are also studied.

hep-ph↗

arXiv1996

$η\to π^0 γγ$ decay in the three-flavor Nambu-Jona-Lasinio model

We study the $η\to π^0 γγ$ decay via the quark-box diagram in the three-flavor Nambu--Jona-Lasinio model that includes the $U_A (1)$ breaking effect. We find that the $η$-meson mass, the $η\to γγ$ decay width and the $η\to π^0 γγ$ decay width are in good agreement with the experimental values when the $U_A (1)$ breaking is strong and the flavor $SU(3)$ singlet-octet mixing angle $θ$ is about zero. The photon energy and the photon invariant mass spectra in $η\to π^0 γγ$ are compared with those in the chiral perturbation theory.

hep-ph↗

arXiv1995

Effects of the $U_A(1)$ Anomaly on $η\to 2 γ$ Decay

We study the $η\to 2 γ$ decay using an extended three-flavor Nambu-Jona-Lasinio model that includes the 't~Hooft instanton induced interaction. The $η$ meson mass and the $η\to 2 γ$ decay width are reproduced simultaneously with a rather strong instanton induced interaction. The calculated $η$ decay constant is $f_η= 2.23 f_π$ and it suggests that the $η$ meson is no longer the Goldstone boson.

hep-ph↗

arXiv1995

$K \to 2 π$ Decay in the Nambu-Jona-Lasinio Model

We study the $K \to 2 π$ decays using the $U_L(3) \times U_R(3)$ version of the Nambu-Jona-Lasinio model with the effective $ΔS = 1$ nonleptonic weak interaction. The $ΔI = {3/2}$ amplitude is in reasonable agreement with experimental data. On the other hand, the calculated $ΔI = {1/2}$ amplitudes strongly depend on the mass of the low-lying scalar-isoscalar $σ$ meson, and therefore give a strong constraint on the parameters of the model.

hep-ph↗