Spectral function of the η′\eta' meson in nuclear medium based on phenomenological models

The in-medium modification of the spectral function of the $\eta'$ meson with and without the spatial momentum is studied with the $T\rho$ approximation by employing two phenomenological models for the $\eta'N$ scattering; one is called \com{coupled channels model} and the other the $N(1895)$-dominance model. In the former model, the $\eta'N$ scattering amplitude is calculated in the unitarized coupled-channel approach involving the $\eta'N$ channel, while in the latter model the $\eta'N$ scattering process is dominated by the $N(1895)$ resonance with the spin and parity $J^P=1/2^-$. In the \com{coupled channels model}, one single peak of the in-medium $\eta'$ mode appears in the spectral function and the peak position shifts to higher energies along with the increase of the nuclear density reflecting the repulsive $\eta'N$ scattering length of the unitarized coupled-channel amplitude. On the other hand, two branches related to the $\eta'$ and $N(1895)$-hole modes appear in the $N(1895)$-dominance model. In both models, the shift of the peak position and the width in the spectral function are a few tens of MeV at the normal nuclear density for the $\eta'$ meson at rest in the nuclear medium. Once the spatial momentum is turned on, the peak positions in the spectral function approach the energies without the nuclear medium effect. Particularly, in the $N(1895)$-dominance model, the peak strength of the $N(1895)$-hole mode gets smaller with the finite momentum and the spectral function comes to have one single peak.Comment: 16 pages, 14 figure

η′\eta^\prime meson under partial restoration of chiral symmetry in nuclear medium

In-medium modification of the eta' mass is discussed in the context of partial restoration of chiral symmetry in nuclear medium. We emphasize that the U_A(1) anomaly effects causes the eta'-eta mass difference necessarily through the chiral symmetry breaking. As a consequence, the eta' mass is expected to be reduced by order of 100 MeV in nuclear matter where about 30% reduction of chiral symmetry takes place. The strong attraction relating to the eta' mass generation eventually implies that there should be also a strong attractive interaction in the scalar channel of the eta'-N two-body system. We find that the attraction can be strong enough to form a bound state.Comment: 4 pages, 3 figures. Talk given at the XI International Conference on Hypernuclear and Strange Particle Physics (HYP2012), Oct. 1-5, 2012, Barcelona, Spain. Accepted version. Some typos were correcte

Application of tensor network method to two dimensional lattice N=1\mathcal{N}=1 Wess-Zumino model

We study a tensor network formulation of the two dimensional lattice $\mathcal{N}=1$ Wess-Zumino model with Wilson derivatives for both fermions and bosons. The tensor renormalization group allows us to compute the partition function without the sign problem, and basic ideas to obtain a tensor network for both fermion and scalar boson systems were already given in previous works. In addition to improving the methods, we have constructed a tensor network representation of the model including the Yukawa-type interaction of Majorana fermions and real scalar bosons. We present some numerical results.Comment: 8 pages, 4 figures, talk presented at the 35th International Symposium on Lattice Field Theory (Lattice 2017), 18-24 June 2017, Granada, Spai