arXiv subjects

Makoto Takizawa

Publications and source records attributed to Makoto Takizawa.

21 records · Page 2Linked to original sources

arXiv2006

η- and η'-mesic nuclei and U_A(1) anomaly at finite density

We discuss theoretically the possibility of observing the bound states of the ηand η'(958) mesons in nuclei. We apply the NJL model to study the ηand η' meson properties at finite density and calculate the formation cross sections of the ηand η' bound states with the Green function method for (γ,p) reaction. We also discuss the experimental feasibility at photon facilities like SPring-8. The contributions due to the ωmeson production are also included to obtain the realistic (γ,p) spectra. We conclude that we can expect to observe resonance peaks in (γ,p) spectra for the formation of meson bound states and we can deduce new information on ηand η' properties at finite density. These observations are believed to be essential to know the possible mass shift of η' and deduce new information on the effective restoration of the U_A(1) anomaly in the nuclear medium.

nucl-th↗

arXiv2004

Light Scalar Mesons in the Improved Ladder QCD

The light scalar meson spectrum is studied using the improved ladder QCD with the UA(1) breaking Kobayashi-Maskawa-'t Hooft interaction by solving the Schwinger-Dyson and Bethe-Salpeter equations. The dynamically generated momentum-dependent quark mass is large enough in the low momentum region to give rise to the spontaneous breaking of chiral symmetry. Due to the large dynamical quark mass, the scalar mesons become the q bar{q} bound states. Since the parameters have been all fixed to reproduce the light pseudoscalar meson masses and the decay constant, there is no free parameter in the calculation of the scalar mesons. We obtain $M_{sigma} = 667$ MeV, $M_{a_0} = 942$ MeV and $M_{f_0} = 1336$ MeV. They are in good agreement with the observed masses of $sigma(600)$, $a_0(980)$ and $f_0(1370)$, respectively. We therefore conclude that these states are the members of the light scalar meson nonet. The mass of $K_0^{*}$ is obtained between that of $a_0$ and $f_0$ and the corresponding state is not observed experimentally. We also find that the strangeness content in the $sigma$ meson is about 5%.

hep-ph↗

arXiv2003

U_A(1) Breaking Effects on the Light Scalar Meson Spectrum

Effects of the U_A(1) breaking interaction on the low-lying nonet scalar mesons are studied using the extended Nambu-Jona-Lasinio model. The strength of the U_A(1) breaking interaction is determined by the electromagnetic decays of the eta meson. We find that the U_A(1) breaking interaction gives rise to about 150 MeV mass difference between the sigma and a_0 mesons. We also find that the strangeness content in the σmeson is about 15%. The calculated mass of the I=1/2 state is about 200 MeV heavier than that of the I=1 state. The order of these masses is not likely to change within this model.

hep-ph↗