[en] 5-quark baryon Θ⁺ with S = +1 was discovered in photoproduction from the neutron in ¹²C at LEPS of SPring-8. A Gaussian significance was 4.6σ. The mass and width of the Θ⁺ were 1.54± 0.01 GeV/c² and smaller than 25 MeV/c², respectively. Recent results from other experiments confirmed the existence of the Θ⁺. The Θ⁺ can be interpreted as a molecular meson-baryon resonance or alternatively as an exotic five quark state (uudds(bar)). Photon beam asymmetries for the p(γ, K⁺)Λ and p(γ, K⁺)Σ⁰ reactions were measured at E-γ = 1.5-2.4 GeV and 0.6 < cos(θ^c.m._K+) < 1.0 by using linearly polarized photon beam. The measured asymmetries are positive and gradually increase with rising photon energy. There is no theoretical prediction which perfectly reproduces the measurements. Including the new results in the development of theoretical models is crucial for understanding the reaction mechanism and to test the presence of missing resonances. (author)

[en] We performed the ¹³C(K^-,π^-γ)¹³C experiment at 0.93 GeV/c at the AGS of BNL to obtain the ls-splitting of Λ single particle states in ¹³C with high precision. We succeeded in measuring gamma-rays from the 1/2^- and 3/2^- states, which have predominantly ¹²C(0⁺)xp_Λ configuration, to the GS in ¹³_ΛC by using NaI detectors. The splitting was conclusively found to be ΔE(1/2^- -3/2^-) = +152±54(stat)±36(syst) keV which was almost 1/30 to 1/20 times smaller than that of single particle states in nuclei around this mass region. The excitation energy of the 1/2^- and 3/2^- states was obtained as 10.982±0.031(stat)±0.056(syst) MeV and 10.830±0.031(stat)±0.056(syst)MeV, respectively. The j_Λ=1_Λ-1/2((p_1/2)_Λ) state appeared higher in energy as in normal nuclei, which is consistent with theoretical predictions. This result suggests that the ls-force between a Λ particle and a nucleus is attractive. (S.Y.)

[en] We are carrying out hadron photoproduction experiments by using polarized photon beams with energies of 1.5-2.9 GeV at SPring-8 in Japan. In 2005, we started developing a polarized HD target for future LEPS experiments using both the polarized photon beams and the polarized target. To introduce a polarized target plays an important role in upgrading the LEPS experiments to the next higher step. The measurement of double polarization asymmetries is expected to give important information to investigate the nucleon hidden structure, hadron photoproduction dynamics, and exotic hadron property. We report on the present status of the development of the polarized HD target at RCNP. We will carry out a test experiment to confirm that the polarized HD target can be transported from Osaka university to SPring-8 without any problems in 2010. If we succeed in the test experiment, we will carry out a long experiment to take physics data in 2011-2012. (author)

No abstract available

[en] We carry out photoproduction experiments by using linearly polarized photon beams with energies of 1.5–3.0 GeV at SPring-8/LEPS. There is no distinct peak structure due to nucleon or Δ resonances in the preliminary cross sections for the γp→π⁻Δ⁺⁺, π⁺Δ⁰, and π⁺n reactions for 0.7< cosθ_π <1. The cross section ratios σ(π⁺Δ⁰)/σ(π⁻Δ⁺⁺) are close to 1/3, which is expected from the isospin = 1 exchange in the t-channel, at small π angles and become larger than 1/3 at large π angles. The photon beam asymmetries are small negative values, small positive values, and large positive values for the π⁻Δ⁺⁺, π⁺Δ⁰, and π⁺n reactions, respectively. The asymmetries are sensitive to reaction mechanisms and are found to be largely different among these reactions. The asymmetries are strong constraint in theoretical studies and expected to play an important role in searching for new nucleon resonances. (author)

[en] Photoproduction reactions are dominated by isospin rules. In the case of πΔ photoproduction on the proton at forward π angles, the exchange of isospin = 1 meson(π or ρ) in the t-channel is the most dominant reaction mechanism, which is considered to give a cross section ratio σ(π⁺Δ⁰)/σ(π⁻Δ⁺⁺) of 1/3. The cross section ratio has not been measured precisely experimentally. We present preliminary results for the cross section ratio at E_γ = 1.5–3.0 GeV. Larger ratios than 1/3 measured by our experiment at LEPS/SPring-8 suggest that the d̄d productions are enhanced compared with the ūu productions in the photoproduction reactions on the proton.

[en] Every thermoelectric material shows high performance at a specific narrow temperature range. The temperature range with high performance can be expanded by joining the materials with different peak temperature. This is the concept of an FGM. The FGMs for Peltier cooling materials have never been reported though the FGMs for thermoelectric power generation were reported to enhance conversion efficiency. Bismuth telluride is the best material for cooling devices at around room temperature. Then we investigated the thermoelectric cooling properties for bismuth telluride with two steps graded structure FGM. Two kinds of melt-grown materials of p-type bismuth telluride (hereafter, sample 1 and sample 2) were used. The samples 1 and 2 of 3 mm square x 2.5 mm were joined to form an FGM of 3 mm square x 5 mm in length by soldering with ultrasonic vibration. Thermoelectric cooling properties were evaluated by observing the maximum temperature drop to electric current when the high temperature side was kept constant. When the high temperature side is kept at 370 K, the temperature drop of the monolithic sample 1 was 34.6 K, and 39.7 K for sample 2, because of the difference of the carrier density. In the case of the FGM, the temperature drop was 45.2 K when the sample 1 was placed at the high temperature side. On the other hand, the temperature drop was only 27.6 K when the sample 2 was placed at the high temperature side. From these results, it is clear that high performance can be obtained by forming an FGM when the proper material arrangement is performed along the temperature gradient. (orig.)

[en] We carry out photoproduction experiments by using linearly polarized photon beams with energies of 1.5-3 GeV at SPring-8/LEPS. One of our physics motivations is to understand reaction mechanisms of hadron photoproduction. We study (1) y^→p→ π^-Δ⁺⁺, (2) y^→p→ π⁺n, (3) y^→p→ K⁺Λ(K⁺Σ⁰), and (4) y^→p→ π⁺Δ⁰ reactions which produce (1) uu, (2) dd, (3) ss, and (4) dd quark-antiquark pairs in the final state. Differential cross sections and photon beam asymmetries have been measured at forward meson angles of 0.6 < cos θ_cm<1. Precise comparison between the π^-Δ⁺⁺ and π⁺Δ⁰ reactions plays an important role in the study of nucleon resonances. It enables to distinguish between N* and Δ* by taking the cross section ratios of the two reactions. We have measured preliminary cross section ratios dσ(π⁺Δ⁰)/dσ(π^-Δ⁺⁺). The ratios are found to be close to 1/3, which is expected from the exchange of isospin=1 in the t channel, for 0.966< cos θ_cm<1 and all the photon energies. The ratios become larger than 1/3 and close to 1 for larger angles and higher energy regions. The larger ratios might be due to A resonances, giving the ratio 4/3, excited in the intermediate state

[en] Thermoelectric materials can directly convert thermal energy into electrical power. The thermoelectric property of every thermoelectric material has temperature dependence and a high performance appears at a specific temperature. If the proper materials with different carrier concentrations and/or compositions are placed and joined along the temperature gradient, the performance should be higher than a monolithic material. Pb-Te is generally used for thermoelectric power generation at the medium temperature range between 500 and 800 K. The performance of PbTe with different carrier concentration, however, is not high enough at the high temperature range. Then, it is also insufficient as a component for an FGM, as it is necessary for every part of an FGM to show high performance. In order to improve the thermoelectric properties, we investigated the effects of Ge on thermoelectric properties for PbTe added with GeTe as a component of an FGM. The melt grown materials of PbTe added with GeTe were prepared by vertical Bridgman method. The GeTe content range was from 0 to 15 mol%. Crystal structure of each part of the ingot was identified by means of XRD. The microstructure of each ingot was observed by scanning electron microscopy. The temperature dependence of electrical resistivity, Hall coefficient, Seebeck coefficient and thermal conductivity were measured over the temperature range from 300 to 700 K. From the results of XRD, the ingots with above 10 mol%GeTe consisted of two phases of PbTe and GeTe. Dimensionless figure of merit, ZT, was calculated from results of thermoelectric properties. The PbTe with 10 mol%GeTe showed a largest ZT of 1.19 at 500 K, which is rather promising for a component of an FGM. (orig.)

[en] The spin-orbit splitting of Λ single-particle states in ¹³_Λ C was measured. The ¹³C( K^-,π^-)¹³_ΛC reaction was used to excite both the 1/2^- and 3/2^- states simultaneously, which have predominantly ¹²C( 0⁺)xp_Λ configuration. γ rays from the states to the ground state were measured in coincidence with the π^- 's, by which ells splitting was found to be 152±54(stat)±36(syst )keV . The value is 20--30times smaller than exhibited by the ells splitting in the nuclear shell model. This value gives us new insight into the YN interaction