Jau-Ann Chen

Photoproduction ofΛ(1405)andΣ0(1385)on the proton atEγ=1.5−2.4GeV

Differential cross sections for {gamma}p{yields}K{sup +}{lambda}(1405) and {gamma}p{yields}K{sup +}{sigma}{sup 0}(1385) reactions have been measured in the photon energy range from 1.5 to 2.4 GeV and the angular range of 0.8<cos({theta})<1.0 for the K{sup +} scattering angle in the center-of-mass system. This data is the first measurement of the {lambda}(1405) photoproduction cross section. The line shapes of {lambda}(1405) measured in {sigma}{sup +}{pi}{sup -} and {sigma}{sup -}{pi}{sup +} decay modes were different with each other, indicating a strong interference of the isospin 0 and 1 terms of the {sigma}{pi} scattering amplitudes. The ratios of {lambda}(1405) production to {sigma}{sup 0}(1385) production were measured in two photon energy ranges: near the production threshold (1.5<E{sub {gamma}}<2.0 GeV) and far from it (2.0<E{sub {gamma}}<2.4 GeV). The observed ratio decreased in the higher photon energy region, which may suggest different production mechanisms and internal structures for these hyperon resonances.

Search for

A search forKpp bound state (the lightest kaonic nucleus) has been performe d using theγd → KπX reaction at Eγ=1.5-2.4 GeV at LEPS / Pring-8. The di fferential cross section of Kπ photo-production o ff deuterium has been measured for the first time in this energy region, and a bump st ructure was searched for in the inclusive missing mass spectrum. A statistically significant bump structure was no t observed in the region from 2.22 to 2.36 GeV /c2, and the upper limits of the di fferential cross section for the Kpp bound state production were determined to be 0.1 − 7μ b (95% confidence level) for a set of assumed binding energy and width values.

K^-pp

Photoproduction of Lambda(1520) with liquid hydrogen and deuterium targets was examined at photon energies below 2.4 GeV in the SPring-8 LEPS experiment. For the first time, the differential cross sections were measured at low energies and with a deuterium target. A large asymmetry of the production cross sections from protons and neutrons was observed at backward K+/0 angles. This suggests the importance of the contact term, which coexists with t-channel K exchange under gauge invariance. This interpretation was compatible with the differential cross sections, decay asymmetry, and photon beam asymmetry measured in the production from protons at forward K+ angles.

bound state via

We briefly review recent work on universal finite-size scaling functions (UFSSFs) and quantities in percolation models. The topics under discussion include: (a) UFSSFs for the existence probability (also called crossing probability) Ep, the percolation probability P, and the probability Wn of the appearance of n percolating clusters, (b) universal slope for average number of percolating clusters, (c) UFSSFs for a q-state bond-correlated percolation model corresponding to the q-state Potts model. We also briefly mention some very recent related developments and discuss implications of our results.

\gamma d \rightarrow K^+ \pi^-X

Using a histogram Monte Carlo simulation method, we calculate the existence probability for bond percolation on simple cubic (sc) and body-centred cubic (bcc) lattices, and site percolation on sc lattices with free boundary conditions. The spanning rule considered by Reynolds, Stanley, and Klein is used to define percolating clusters. We find that for such systems has very good finite-size scaling behaviour and the value of at the critical point is universal and is about .

reaction at

Differential cross sections at

E_\gamma=1.5-2.4

t=t_{\text{min}}

GeV

and decay asymmetries for the

Near-threshold photoproduction of Lambda(1520) from protons and deuterons

\gamma p\rightarrow\phi p

Universal scaling functions and quantities in percolation models

reaction have been measured using linearly polarized photons in the range 1.5 to 2.9 GeV. These cross sections were used to determine the Pomeron strength factor. The cross sections and decay asymmetries are consistently described by the