Generalized form factors and spin structures of the kaon

We investigate the spin structure of the kaon, based on the nonlocal chiral quark model from the instanton vacuum. We first revisit the electromagnetic form factors of the pion and kaon, improving the results for the kaon. We evaluate the generalized tensor form factors of the kaon in order to determine the probability density of transversely polarized quarks inside the kaon. We consider the effects of flavor SU(3) symmetry breaking, so that the probability density of the up and strange quarks are examined in detail. It is found that the strange quark behaves differently inside the kaon in comparison with the up quark.Comment: 9 pages, 7 figures, accepted for publication in Phys. Lett.

Pion properties at finite density

In this talk, we report our recent work on the pion weak decay constant (F_pi) and pion mass (m_pi) using the nonlocal chiral quark model with the finite quark-number chemical potential (mu) taken into account. Considering the breakdown of Lorentz invariance at finite density, the time and space components are computed separately, and the corresponding results turn out to be: F^t_pi = 82.96 MeV and F^s_pi = 80.29 MeV at mu_c ~ 320 MeV, respectively. Using the in-medium Gell-Mann Oakes-Renner (GOR) relation, we show that the pion mass increases by about 15% at mu_c.Comment: 5 pages, 2 figures, Talk given at the 4th Asia-Pacific Conference on Few-Body Problems in Physics 2008 (APFB08), 19 ~ 23 Aug 2008, Depok, Indonesi

Chemical phosphate removal from wastewaters

Two subjects in chemical phosphate removal were investigated in this study: rapid mixing and modeling. Evaluation of rapid-mixing parameters showed that chemical phosphate removal is affected by the mixing intensity, the mixing time, and aluminum solution strength. Phosphate removal efficiency improved as the mixing intensity increased from a mean velocity gradient (G) value of 150 to 600 sec[superscript]-1. Further increase in a G value was not accompanied by improvement of phosphate removal efficiency. This indicates that an optimum mixing intensity for chemical phosphate removal is a G value of 600 sec[superscript]-1. The effect of the mixing time was found insignificant when it was in the range of 10-60 seconds. After that, phosphate removal efficiency deteriorated over time when the mixing time was increased up to 180 seconds. The time trend was found to be linear and constant at G values of 500-1000 sec[superscript]-1. The higher the aluminum solution strength, the better was the phosphate removal efficiency;The modeling study found that phosphates were removed by forming aluminum hydroxyphosphate, Al[subscript]1.2H[subscript]2PO[subscript]4(OH)[subscript]2.6, rather than aluminum phosphate in chemical phosphate removal. It was also shown that calcium-phosphate precipitation could occur at an initial stage of chemical phosphate removal when calcium was present in the wastewater. The precipitates could be tricalcium phosphate. Aluminum chloride and alum were compared in their effects on chemical phosphate removal. There was no difference between use of these two chemicals. Evaluation of the Ferguson model for phosphate removal revealed that the Ferguson model predicted the residual phosphate values well. However, the model was found to be more like data fitting because it did not incorporate complexes and cannot account for use of different chemical effects. Regression models were developed for the residual alkalinity, pH, and phosphate. These regression models predicted the residual parameters well

Twist-3 pion and kaon distribution amplitudes from the instanton vacuum with flavor SU(3) symmetry breaking

We investigate the twist-3 pion and kaon distribution amplitudes of the pseudoscalar (phi^p_{pi,K}) and pseudotensor (phi^{sigma}_{pi,K}) types, based on the effective chiral action from the instanton vacuum. Effects of flavor SU(3) symmetry breaking are explicitly taken into account. The Gegenbauer moments and the moments of the distribution amplitudes () are also computed. Our results are summarized as follows: a^p_{2,pi} ~ 0.4, a^p_{1,K} ~ 0.02 and a^p_{2,K} ~ 0.14, and a^{sigma}_{2,pi} ~ 0.02 and a^{sigma}_{1,K} ~ a^{sigma}_{2,K} ~ 0; ^p_{\pi} ~ ^p_K ~ 0.37 and ^p_K ~ 0, and ^{sigma}_{pi} ~ ^{sigma}_K ~ 0.20 and ^{sigma}_K ~ 0. We compare our results with those from the QCD sum rules. We also discuss the relevant Wilson coefficients which were analyzed recently in chiral perturbation theory.Comment: 12 pages, 4 figures, accepted for publication in PR

Photon and nucleon induced production of Theta^+

We investigate Theta^+ production via photon and nucleon induced reactions. We observe that the positive parity Theta^+ production provides about ten times larger total cross sections than those of the negative parity one in both photon and nucleon induced reactions due to P-wave enhancement of the K-N-Theta vertex. We also consider the model independent method in the nucleon induced reaction to determine the parity of Theta^+ and show clearly distinguishable signals for the two parities.Comment: 4 pages, 8 figures, Talk given at International Workshop on PENTAQUARK04, Spring-8, Hyogo, Japan, 20-23 Jul 200