Formation of Kaonic Atoms and Kaonic Nuclei by In-flight (K−,pK^-,p) reactions

We study the kaonic atom and kaonic nucleus formation by the in-flight ($K^-, p$) reactions for C, O, Si and Ca target cases theoretically. Deeply bound kaonic atoms were predicted to exist as quasi-stable states and were expected to be observed in some proper experimental methods. Kaonic nuclear states are also expected to exist with large decay widths. We evaluate the formation cross sections of the kaonic atoms and kaonic nuclei using an effective number approach. We show that the indications of the kaonic bound states can be observed in the outgoing proton energy spectra.Comment: 17 pages, 11 figures: Minor corrections made. Results and Conclusion do not chang

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

Formation of \eta'(958)-mesic nuclei and axial U_A(1) anomaly at finite density

We discuss the possibility to produce the bound states of the $\eta'(958)$ meson in nuclei theoretically. We calculate the formation cross sections of the $\eta'$ bound states with the Green function method for ($\gamma$,p) reaction and discuss the experimental feasibility at photon facilities like SPring-8. We conclude that we can expect to observe resonance peaks in ($\gamma$,p) spectra for the formation of $\eta'$ bound states and we can deduce new information on $\eta'$ properties at finite density. These observations are believed to be essential to know the possible mass shift of $\eta'$ and deduce new information of the effective restoration of the chiral $U_A(1)$ anomaly in the nuclear medium.Comment: 4 pages, 3 figure

Fast Vacuum Decay into Quark Pairs in Strong Color Electric and Magnetic Fields

We study quark-pair creations in strong color electromagnetic fields. We point out that, for massless quarks, the vacuum persistency probability per unit space-time volume is zero, i.e., the quark-pair creation rate w is infinite, in general homogeneous color electromagnetic fields, while it is finite when the color magnetic field is absent. We find that the contribution from the lowest Landau level (LLL) dominates this phenomenon. With an effective theory of the LLL projection, we also discuss dynamics of the vacuum decay, taking into account the back reaction of pair creations.Comment: 4 pages, 1 figure, contribution to the proceedings of International conference on the structure of baryons (BARYONS'10), RCNP, Osaka, Japan, Dec. 7-11, 2010; fig.2 delete