0000000000418641
AUTHOR
Takashi Inoue
Chiral unitary approach to hadron spectroscopy
The s-wave meson-baryon interaction in the $S = -1$, $S= 0$ and $S= -2$ sectors is studied by means of coupled channels, using the lowest-order chiral Lagrangian and the N/D method or equivalently the Bethe-Salpeter equation to implement unitarity. This chiral approach leads to the dynamical generation of the $\Lambda (1405)$, $\Lambda(1670)$ and $\Sigma(1620)$ states for $S = -1$, the $N^*(1535)$ for $S= 0$ and the $\Xi(1620)$ for $S= -2$. We look for poles in the complex plane and extract the couplings of the resonances to the different final states. This allows identifying the $\Lambda (1405)$ and the $\Lambda(1670)$ resonances with $\bar{K}N$ and $K\Xi$ quasibound states, respectively. …
Second asymptomatic carotid surgery trial (ACST-2): a randomised comparison of carotid artery stenting versus carotid endarterectomy.
Summary Background Among asymptomatic patients with severe carotid artery stenosis but no recent stroke or transient cerebral ischaemia, either carotid artery stenting (CAS) or carotid endarterectomy (CEA) can restore patency and reduce long-term stroke risks. However, from recent national registry data, each option causes about 1% procedural risk of disabling stroke or death. Comparison of their long-term protective effects requires large-scale randomised evidence. Methods ACST-2 is an international multicentre randomised trial of CAS versus CEA among asymptomatic patients with severe stenosis thought to require intervention, interpreted with all other relevant trials. Patients were eligib…
Chiral unitary approach to s-wave meson baryon scattering in the strangeness S=0 sector
We study the S-wave interaction of mesons with baryons in the strangeness S=0 sector in a coupled channel unitary approach. The basic dynamics is drawn from the lowest order meson baryon chiral Lagrangians. Small modifications inspired by models with explicit vector meson exchange in the t-channel are also considered. In addition the pi pi N channel is included and shown to have an important repercussion in the results, particularly in the isospin 3/2 sector.
Eta in the nuclear medium within a chiral unitary approach
The self-energy of an eta meson in the nuclear medium is calculated in a chiral unitary approach. A coupled channel Bethe-Salpeter equation is solved to obtain the effective eta-N interaction in the medium. The base model reproduces well the free space pi-N elastic and inelastic scattering at the eta-N threshold or N^*(1535) region. The Pauli blocking on the nucleons, binding potentials for the baryons and self-energies of the mesons are incorporated, including the eta self-energy in a self-consistent way. Our calculation predicts about -54 -i29 MeV for the optical potential at normal nuclear matter for an eta at threshold but also shows a strong energy dependence of the potential.
Eta bound states in nuclei
The energies and widths of bound states of the $\eta$ meson in different nuclei are obtained using the results for its selfenergy in a nuclear medium, which is evaluated in a selfconsistent manner using techniques of unitarized chiral perturbation theory. We find bound states in all studied nuclei (from $^{12}{C}$ on) and the half widths obtained are larger than the separation of the levels, what makes the experimental observation of peaks unlikely. We have paid a special attention to the region of nuclei where only the $1s$ state appears and the binding energies are of the order of magnitude of the half width, which would magnify the chances that some broad peak could be observed. This is …
eta nucleus optical potential in a chiral unitary approach
The self-energy of an eta in a nuclear medium is calculated in a chiral unitary model, and applied to eta states in nuclei. Our calculation predicts an attractive eta nucleus optical potential which can accommodate many eta bound states in different nuclei.