Search

We have constructed a new laser-Compton-scattering facility, called the LEPS2 beamline, at the 8-GeV electron storage ring, SPring-8. This facility provides a linearly polarized photon beam in a tagged energy range of 1.3--2.4 GeV. Thanks to a small divergence of the low-emittance storage-ring electrons, the tagged photon beam has a size (sigma) suppressed to about 4 mm even after it travels about 130 m to the experimental building that is independent of the storage ring building and contains large detector systems. This beamline is designed to achieve a photon beam intensity higher than that of the first laser-Compton-scattering beamline at SPring-8 by adopting the simultaneous injection of up to four high-power laser beams and increasing a transmittance for the long photon-beam path up to about 77%. The new beamline is under operation for hadron photoproduction experiments.

Particle counting analysis (PCA) with a multi-stage scintillation detector shows a new perspective on angularly resolved spectral characterization of GeV-scale, multi-species ion beams produced by high-power lasers. The diagnosis provides a mass-dependent ion energy spectrum based on time-of-flight and pulse-height analysis of single particle events detected through repetitive experiments. With a novel arrangement of multiple scintillators with different ions stopping powers, PCA offers potential advantages over commonly used diagnostic instruments (CR-39, radiochromic films, Thomson parabola, etc .) in terms of coverage solid angle, detection efficiency for GeV-ions, and real-time analysis during the experiment. The basic detector unit was tested using 230-MeV proton beam from a synchrotron facility, where we demonstrated its potential ability to discriminate major ion species accelerated in laser–plasma experiments (i.e., protons, deuterons, carbon, and oxygen ions) with excellent energy and mass resolution. The proposed diagnostic concept would be essential for a better understanding of laser-driven particle acceleration, which paves the way toward all-optical compact accelerators for a range of applications.

We report on the frozen-spin polarized hydrogen-deuteride (HD) targets for photoproduction experiments at SPring-8/LEPS. Pure HD gas with a small amount of ortho-H2 (∼0.1%) and a very small amount of para-D2 (∼0.001%) was liquefied and solidified by liquid helium. The temperature of the produced solid HD was reduced to about 30 mK with a dilution refrigerator. A magnetic field (17 T) was applied to the HD to grow the polarization with the static method. After the aging of the HD at low temperatures in the presence of a high-magnetic field strength for three months, the polarization froze. Almost all ortho-H2 molecules were converted to para-H2 molecules. Most remaining para-D2 molecules were converted to ortho-D2 molecules. The para-H2 and ortho-D2 molecules exhibited weak spin interactions with the HD. If the concentrations of the ortho-H2 and para-D2 were reduced appropriately at the beginning of the aging process, the aging time can be shortened. We have developed a new nuclear magnetic resonance (NMR) system to measure the relaxation times (T1) of the 1H and 2H nuclei with two frequency sweeps at the respective frequencies of 726 MHz and 111 MHz and succeeded in the monitoring of the polarization build-up at decreasing temperatures from 600 mK to 30 mK at 17 T. Automatic NMR measurements with the frequency sweeps enabled us to omit the use of a manual tuning circuit and to remove magnetic field sweeps with eddy current heat. This technique enables us to optimize the concentration of the ortho-H2 and to efficiently polarize the HD target within a shortened aging time.

The $\mathrm{Nd}^{3+}$ doped $\mathrm{LaAlO}_3$ crystal is a good candidate of a polarized $^{139}\mathrm{La}$ target for the search of the P-odd and T-odd interaction in the low-energy neutron absorption of $^{139}\mathrm{La}$. As the first step for realizing the polarized $^{139}\mathrm{La}$ target, we grow the undoped $\mathrm{LaAlO}_3$ crystal and the $\mathrm{La}_{1-x}\mathrm{Nd}_x\mathrm{AlO}_3$ ($x=5 \times 10^{-4}$) crystal by floating-zone method with four halogen lamps. The ESR measurements of $\mathrm{Nd}^{3+}$ in the latter crystal indicated that the linewidth was about 6 gauss, whose value is the same as the crystal in which 50 % $^{139}\mathrm{La}$ polarization was achieved in the previous DNP experiment. As the result, the crystals grown by this method can be applicable to the target study for the T-violation search.

The nuclear spin-lattice relaxation time ($T_1$) of lanthanum and aluminum nuclei in a single crystal of lanthanum aluminate doped with neodymium ions is studied to estimate the feasibility of the dynamically polarized lanthanum target applicable to beam experiments. The application of our interest is the study of fundamental discrete symmetries in the spin optics of epithermal neutrons. This study requires a highly flexible choice of the applied magnetic field for neutron spin control and favors longer $T_1$ under lower magnetic field and at higher temperature. The $T_1$ of $^{139}{\rm La}$ and ${}^{27}{\rm Al}$ was measured under magnetic fields of $0.5$-$2.5$ T and at temperatures of $0.1$-$1.5$ K and found widely distributed up to 100 h. The result suggests that the $T_1$ can be as long as $T_1 \sim$ 1 h at $0.1$ K with a magnetic field of $0.1$ T, which partially fulfills the requirement of the neutron beam experiment. Possible improvements to achieve a longer $T_1$ are discussed., Comment: 10 pages, 8 figures

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 Eγ = 1.5–3.0 GeV. Larger ratios than 1/3 measured by our experiment at LEPS/SPring-8 suggest that the dd productions are enhanced compared with the ūu productions in the photoproduction reactions on the proton.

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 θcm -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 θcm

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 $$\varDelta $$ resonances in the preliminary cross sections for the $$\gamma p$$ $$\rightarrow $$ $$\pi ^{-}\varDelta ^{++}$$ , $$\pi ^{+}\varDelta ^{0}$$ , and $$\pi ^{+}n$$ reactions for 0.7 $$

Differential cross sections and photon-beam asymmetries for the γ[over →]p→π^{-}Δ^{++}(1232) reaction have been measured for 0.7

The differential cross sections and decay angular distributions for coherent $\phi$-meson photoproduction from helium-4 have been measured for the first time at forward angles with linearly polarized photons in the energy range $E_{\gamma} = \text{1.685-2.385 GeV}$. Thanks to the target with spin-parity $J^{P} = 0^{+}$, unnatural-parity exchanges are prohibited, and thus natural-parity exchanges can be investigated clearly. The decay asymmetry with respect to photon polarization is shown to be very close to the maximal value. This ensures the dominance ($> 94\%$) of natural-parity exchanges in this reaction. To evaluate the contribution from natural-parity exchanges to the forward cross section ($\theta = 0^\circ$) for the $\gamma p \rightarrow \phi p$ reaction near the threshold, the energy dependence of the forward cross section ($\theta = 0^\circ$) for the $\gamma {^{4}\text{He}} \rightarrow \phi {^{4}\text{He}}$ reaction was analyzed. The comparison to $\gamma p \rightarrow \phi p$ data suggests that enhancement of the forward cross section arising from natural-parity exchanges, and/or destructive interference between natural-parity and unnatural-parity exchanges is needed in the $\gamma p \rightarrow \phi p$ reaction near the threshold.

Differential cross sections and photon-beam asymmetries for the γ[over →]p→π^{-}Δ^{++}(1232) reaction have been measured for 0.7cosθ_{π}^{c.m.}1 and E_{γ}=1.5-2.95 GeV at SPring-8/LEPS. The first-ever high statistics cross-section data are obtained in this kinematical region, and the asymmetry data for 1.5E_{γ}(GeV)2.8 are obtained for the first time. This reaction has a unique feature for studying the production mechanisms of a pure uu[over ¯] quark pair in the final state from the proton. Although there is no distinct peak structure in the cross sections, a non-negligible excess over the theoretical predictions is observed at E_{γ}=1.5-1.8 GeV. The asymmetries are found to be negative in most of the present kinematical regions, suggesting the dominance of π exchange in the t channel. The negative asymmetries at forward meson production angles are different from the asymmetries previously measured for the photoproduction reactions producing a dd[over ¯] or an ss[over ¯] quark pair in the final state. Advanced theoretical models introducing nucleon resonances and additional unnatural-parity exchanges are needed to reproduce the present data.

We report the measurement of the $\gamma p \rightarrow K^{+}\Lambda$ and $\gamma p \rightarrow K^{+}\Sigma^{0}$ reactions at SPring-8. The differential cross sections and photon-beam asymmetries are measured at forward $K^{+}$ production angles using linearly polarized tagged-photon beams in the range of $E_{\gamma}=1.5$--3.0 GeV. With increasing photon energy, the cross sections for both $\gamma p \rightarrow K^{+}\Lambda$ and $\gamma p \rightarrow K^{+}\Sigma^{0}$ reactions decrease slowly. Distinct narrow structures in the production cross section have not been found at $E_{\gamma}=1.5$--3.0 GeV. The forward peaking in the angular distributions of cross sections, a characteristic feature of $t$-channel exchange, is observed for the production of $\Lambda$ in the whole observed energy range. A lack of similar feature for $\Sigma^{0}$ production reflects a less dominant role of $t$-channel contribution in this channel. The photon-beam asymmetries remain positive for both reactions, suggesting the dominance of $K^{*}$ exchange in the $t$ channel. These asymmetries increase gradually with the photon energy, and have a maximum value of +0.6 for both reactions. Comparison with theoretical predictions based on the Regge trajectory in the $t$ channel and the contributions of nucleon resonances indicates the major role of $t$-channel contributions as well as non-negligible effects of nucleon resonances in accounting for the reaction mechanism of hyperon photoproduction in this photon energy regime.

Differential cross sections at $t={t}_{\text{min}}$ and decay asymmetries for the $\ensuremath{\gamma}p\ensuremath{\rightarrow}\ensuremath{\phi}p$ 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 $t$-channel Pomeron and pseudoscalar exchange model in the ${E}_{\ensuremath{\gamma}}$ region above 2.37 GeV. In the lower energy region, an excess over the model prediction is observed in the energy dependence of the differential cross sections at $t={t}_{\text{min}}$. This observation suggests that additional processes or interference effects between Pomeron exchange and other processes appear near the threshold region.

A search for the K − p p bound state (the lightest kaonic nucleus) has been performed using the γ d → K + π − X reaction at E γ = 1.5 – 2.4 GeV at LEPS/SPring-8. The differential cross section of the K + π − photo-production off deuterium ( d 2 σ / d cos θ K + l a b / d cos θ π − l a b ) has been measured for the first time in this energy region. A peak structure was searched for in the inclusive missing mass spectrum. A statistically significant peak structure was not observed in the region from 2.22 to 2.36 GeV/c2. The upper limits of the differential cross section of the K − p p bound state production were determined to be (0.17–0.55), (0.55–1.7) and (1.1–2.9) μb at 95% confidence level with the assumed widths of 20 MeV, 60 MeV and 100 MeV.

The project in producing the hyperpolarized 3He and 19F are addressed in pursuit of radiation free medical diagnosis. The program for production of the hyperpolarized 3He by the brute force method with the Pomeranchuk cooling and the rapid melting of the solid 3He started a few years ago, and is still on the way, while a new program for production of the hyperpolarized 19F by means of the PHIP (ParaHydrogen Induced Polarization) has just got started. Particular attention is placed upon a new idea of the hyperpolarization catalyst to be used for 19F.

The thermal conductivity of a hydrogen deuteride (HD) single crystal is measured at 3–7 K for two mutually perpendicular directions of heat flow in the crystal. The HD sample is prepared by direct crystallization from ultra high-purity HD gas. A typical anisotropy with a ratio of nearly tenfold is obtained for the thermal conductivity in the measured temperature region. Approximate calculations of the anisotropic thermal conductivity in the HD crystal are performed using an analytical formulation of the two-dimensional anisotropic heat conduction, while taking into account cross-plane coupling of phonon Umklapp scattering. The approximate calculations are found to be in reasonable agreement with the experimental results.

The $\ensuremath{\phi}\text{\ensuremath{-}}\mathrm{\ensuremath{\Lambda}}(1520)$ interference effect in the $\ensuremath{\gamma}p\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}p$ reaction has been measured for the first time in the energy range from 1.673 to 2.173 GeV. The relative phases between $\ensuremath{\phi}$ and $\mathrm{\ensuremath{\Lambda}}(1520)$ production amplitudes were obtained in the kinematic region where the two resonances overlap. The measurement results support strong constructive interference when ${K}^{+}{K}^{\ensuremath{-}}$ pairs are observed at forward angles but destructive interference for proton emission at forward angles. Furthermore, the observed interference effect does not account for the $\sqrt{s}=2.1\text{ }\text{ }\mathrm{GeV}$ bump structure in forward differential cross sections for $\ensuremath{\phi}$ photoproduction. This fact suggests possible exotic structures such as a hidden-strangeness pentaquark state, a new Pomeron exchange, or rescattering processes via other hyperon states.

The ϕ-Λ(1520) interference effect in the γp→K^{+}K^{-}p reaction has been measured for the first time in the energy range from 1.673 to 2.173 GeV. The relative phases between ϕ and Λ(1520) production amplitudes were obtained in the kinematic region where the two resonances overlap. The measurement results support strong constructive interference when K^{+}K^{-} pairs are observed at forward angles but destructive interference for proton emission at forward angles. Furthermore, the observed interference effect does not account for the sqrt[s]=2.1 GeV bump structure in forward differential cross sections for ϕ photoproduction. This fact suggests possible exotic structures such as a hidden-strangeness pentaquark state, a new Pomeron exchange, or rescattering processes via other hyperon states.

A portable NMR polarimeter system has been developed to measure the polarization of a polarized Hydrogen-Deuteride (HD) target for hadron photoproduction experiments at SPring-8. The polarized HD target is produced at the Research Center for Nuclear Physics (RCNP), Osaka university and is transported to SPring-8. The HD polarization should be monitored at both places. We have constructed the portable NMR polarimeter system by replacing the devices in the conventional system with the software system with PCI eXtensions for Instrumentation (PXI). The weight of the NMR system is downsized from 80 kg to 7 kg, and the cost is reduced to 25%. We check the performance of the portable NMR polarimeter system. The signal-to-noise (S/N) ratio of the NMR signal for the portable system is about 50% of that for the conventional NMR system. This performance of the portable NMR system is proved to be compatible with the conventional NMR system for the polarization measurement., Comment: 6 page, 8 figures, 2011/Mar/9 Replace Authors

We report measurements of differential cross sections and decay asymmetries of incoherent ϕ-meson photoproduction from the deuteron at forward angles using linearly polarized photons at E γ = 1.5 – 2.4 GeV . The nuclear transparency ratio for the deuteron shows a large suppression, and is consistent with the A-dependence of the ratio observed in a previous measurement with nuclear targets. The reduction for the deuteron cannot be adequately explained in term of isospin asymmetry. The present results suggest the need of refining our understanding of the ϕ–N interaction within a nucleus.

Differential cross sections and decay asymmetries for coherent $\phi$-meson photoproduction from deuterons were measured for the first time at forward angles using linearly polarized photons at $E_{\gamma}$= 1.5-2.4 GeV. This reaction offers a unique way to directly access natural-parity Pomeron dynamics and gluon exchange at low energies. The cross sections at zero degrees increase with increasing photon energy. The decay asymmetries demonstrate a complete dominance of natural-parity exchange processes, showing that isovector unnatural-parity $\pi$-meson exchange is small. Nevertheless the deduced cross sections of $\phi$-mesons from nucleons contributed by isoscalar t-channel exchange processes are not well described by the conventional Pomeron model., Comment: 14 pages, 6 figures. Final published version

We developed a trigger system for the measurement of proton-induced rare hadronic reactions around the beam kinetic energy T p = 400 MeV based on highly segmented trigger scintillation detectors and programmable logic modules. The trigger system was designed to enhance events with the negative-pion production by the difference of the curvatures of the particle tracks in a magnetic field. Since the production cross-section of the negative-pion by the proton-induced reactions was smaller by about 3 orders of magnitude than the total cross-section around the beam energy, we expected large reduction of the trigger rate by the negative-pion selection. The construction of the trigger system was not trivial due to a large detector acceptance that was inevitable to measure the rare reactions. The performance of the trigger system was evaluated by using T p = 430 MeV proton beams. An excellent reduction, more than 2 orders of magnitude reduction, of the background events was achieved.

Differential cross sections and photon beam asymmetries for π 0 photoproduction have been measured at E γ = 1.5 – 2.4 GeV and at the π 0 scattering angles, − 1 cos Θ c . m . − 0.6 . The energy-dependence of differential cross sections for u-channel π 0 production has been determined. An enhancement at backward angles is found above E γ = 1.9 GeV . This is likely to be due to u-channel diagrams. Photon beam asymmetries have been obtained for the first time at backward angles, showing a strong angular dependence at E γ > 2.0 GeV .

Photon beam asymmetries for the γ → p → K + Λ and γ → p → K + Σ 0 reactions have been measured for the photon energy range from 1.5 GeV to 2.4 GeV and for the angular range of 0 ° Θ cm K + 60 ° at the SPring-8/LEPS facility. The observed asymmetries are found to be positive and increase with increasing the photon energy. Present theoretical calculations do not reproduce the data. To extend our knowledge on the K + photoproduction mechanism including the effect of nucleon resonances, further theoretical development is required to fit both the cross section and asymmetry data.

The photo-production of ϕ mesons from Li, C, Al, and Cu at forward angles has been measured at E γ = 1.5 – 2.4 GeV . The number of events for incoherent ϕ photo-production is found to have a target mass number dependence of A 0.72 ± 0.07 in the kinematical region of | t | ⩽ 0.6 GeV 2 / c 2 . The total cross section of the ϕ –nucleon interaction, σ ϕ N , has been estimated as 35 −11 +17 mb using the A -dependence of the ϕ photo-production yield and a Glauber-type multiple scattering theory. This value is much larger than σ ϕ N in free space, suggesting that the ϕ properties might change in the nuclear medium.

A high quality beam of linearly polarized photons of several GeV will become available with the coherent bremsstrahlung technique at JLab. We have developed a polarimeter which requires about two meters of the beam line, has an analyzing power of 20% and an efficiency of 0.02%. The layout and first results of a polarimeter test on the laser back-scattering photon beam at SPring-8/LEPS are presented. A high quality beam of linearly polarized photons of several GeV will become available with the coherent bremsstrahlung technique at JLab. We have developed a polarimeter which requires about two meters of the beam line, has an analyzing power of 20% and an efficiency of 0.02%. The layout and first results of a polarimeter test on the laser back-scattering photon beam at SPring-8/LEPS are presented.

The γ A → π 0 π 0 X reactions is one of the tools to effectively investigate partial restoration of chiral symmetry. An experiment was performed at the LEPS/SPring-8 facility using various nuclear targets. In this experiment, a 2π calorimeter consisting of 252 Lead/SCIFI modules was used to detect the photons coming from the π 0 π 0 decay. A preliminary analysis shows that π 0 π 0 X events are observed.

We have constructed a Time Projection Chamber (TPC) as the 4π detector for hadron photoproduction experiments at SPring-8. A feature of this TPC is to detect low momentum hyperons as close as 16 mm from the target center. We have studied basic performances of the TPC such as the resolution of dE / dx measurement and the spatial resolution with cosmic rays. The resolution of dE / dx measurement is 16% for minimum ionizing particles. The spatial resolution in pad plane is 280 μm and that along drift direction is 620 μm. The spatial resolution at the distance of 16 mm from the target is obtained to be 400 μm and 880 μm in pad plane and along drift direction respectively.

The BNL-AGS/E929 experiment was carried out to study energy levels of the Λ 13 C hypernucleus by a gamma-ray spectroscopy. Energy splitting of the spin-orbit doublets, 1 2 − and 3 2 − states, was estimated precisely. The excitation energy of the 1st 3 2 + state was also measured. We discuss the symmetric and the anti-symmetric spin-orbit interactions between a Λ particle and a nucleon from the measurement.

The GeV photon beam at SPring-8 is produced by backward-Compton scattering of laser photons from 8 GeV electrons. Polarization of the photon beam is ∼100% at the maximum energy with fully polarized laser photons. We report the status of the new facility and the prospect of hadron physics study with this high quality beam. Preliminary results from the first physics run are presented.

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

We present the design of a 13C active target used in the (K−,π−) reaction measurement for hypernuclear studies. The active target has been fabricated from enriched 13C benzene by adding commercially available laser dyes. The performance of the active target has been tested with a 930 MeV /c kaon beam, and used for the 13C(K−,π−γ)13ΛC reaction measurement to reduce the K− decay in-flight backgrounds.

A candidate for a soft dipole resonance, a dipole oscillation mode between a core cluster and a neutron skin, was observed at ${E}_{x}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}4\ifmmode\pm\else\textpm\fi{}1\mathrm{MeV}$ and with a width of $4\ifmmode\pm\else\textpm\fi{}1\mathrm{MeV}$ in ${}^{6}\mathrm{He}$ via the ${}^{6}\mathrm{Li}({}^{7}\mathrm{Li},{}^{7}\mathrm{Be})$ reaction at an incident energy of $65A\phantom{\rule{0ex}{0ex}}\mathrm{MeV}$ and forward scattering angles including $0\ifmmode^\circ\else\textdegree\fi{}$. Its cross section is deduced to be $\ensuremath{\sigma}(0\ifmmode^\circ\else\textdegree\fi{})\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.9\ifmmode\pm\else\textpm\fi{}0.2\mathrm{mb}/\mathrm{sr}$. This value is comparable to that of the giant dipole resonance simultaneously measured.

For a selective excitation of spin-flip strength, ( 6 Li, 6 He) reactions can be a useful tool, because: a) 6 Li and 6 He have ground-state spin and parity values J π = 1 + and 0 + , respectively; b) 6 He has no particle-stable excited state, thus effects from ejectile excitation can be avoided. The ( 6 Li, 6 He) experiments were performed at 100 MeV/nucleon, at which incident energy the reaction is expected to be single-step dominant. Through the analysis of the good-resolution ( 6 Li, 6 He) data on 13 C, 26 Mg, 27 Al and 58 Ni targets, the evidence for a proportional relationship between 0° cross sections and the corresponding Gamow-Teller transition strengths is examined. Suppression of non-spin flip excitations is discussed based on the hindrance of the excitation of the isobaric analog state.

The isovector electric monopole resonance (IVMR) was studied by the ${}^{60}\mathrm{Ni}{(}^{7}\mathrm{Li}{,}^{7}\mathrm{Be}{)}^{60}\mathrm{Co}$ reaction at 65A MeV and at forward scattering angles including zero degrees. We confirmed the existence of the IVMR at an excitation energy of $20\ifmmode\pm\else\textpm\fi{}2\mathrm{MeV}$ with a width of $10\ifmmode\pm\else\textpm\fi{}2\mathrm{MeV}$ in ${}^{60}\mathrm{Co}$, which is an analog of the ${T}_{0}+1$ isospin component of the IVMR estimated at ${E}_{x}\ensuremath{\approx}31\mathrm{MeV}$ in ${}^{60}\mathrm{Ni}$. The result presently obtained is consistent with previous results using the pion charge-exchange reaction.

The charge-exchange 71Ga(3He,tγ)71Ge reaction was used to study the spin-isospin (Gamow Teller: GT) excitations relevant to the axial-vector charged-weak response for solar neutrinos. High-lying GT states in 71Ge with excitation energies up to one MeV above the neutron threshold were found to have finite γ-decay branches to low-lying states. The GT strengths for relevant states and absorption rates of solar neutrinos through the 71Ga(ν, e)71Ge and 71Ga(ν,eγ)71Ge reactions were derived.

Spin-isospin excitations in ${}^{12}$B and ${}^{12}$N have been studied using the ${}^{12}$C$(d$,${}^{2}$He)${}^{12}$B and ${}^{12}$C${(}^{3}$He,$t)$${}^{12}$N charge-exchange reactions at $\ensuremath{\theta}$ = 0$\ifmmode^\circ\else\textdegree\fi{}$ and at ${E}_{d}$=200 MeV and $E$${(}^{3}$He)=450 MeV, respectively. Neutron decay from ${}^{12}$B to ${}^{11}$B and proton decay from ${}^{12}$N to ${}^{11}$C have been measured with detector arrays consisting of liquid-scintillation counters and silicon detectors, respectively. Microscopic structures of the spin-dipole resonances in ${}^{12}$B and ${}^{12}$N are discussed on the basis of the experimental observations of particle decays and their angular correlations.

A γ-ray detector system “NYMPHS” was built for 7Be-γ coincidence measurements to separate (7Li, 7Beg.s.) and (7Li, 7Be0.43MeV) channels in the (7Li, 7Be) reaction at intermediate energies. NYMPHS is composed of 22 GSO scintillators, each with a volume of about 30 cm3. A typical energy resolution was about 9% at Eγ = 0.66 MeV. The absolute detection efficiency of NYMPHS was 0.200 ± 0.005 for the 0.43 MeV 7Be γ-ray. NYMPHS combined with a magnetic spectrograph showed good performance for 7Be-γ coincidence measurements in the (7Li, 7Be) reactions on 12C and 90Zr targets at EL = 65A MeV.

The ( 7 Li, 7 Be) reaction was found to be used to separate ΔS = 0 and ΔS = 1 transitions through the coincidence measurement of the γ-ray from deexcitation of the 0.43 MeV state of 7 Be at an incident energy of 65 A MeV on 6 Li, 7 Li, 12 C and 90 Zr nuclei. The reaction was shown to proceed predominantly via one-step reaction process. Predominance of one-step process means utility for derivation of spin-flip and non spin-flip strengths for isovector excitations in medium heavy nuclei at intermediate incident energies. The relative nuclear spin-strength P sf was deduced for isovector excitations.

A laser-Compton backscattering beam, which we call a `Laser-Electron Photon' beam, was upgraded at the LEPS beamline of SPring-8. We accomplished the gains in backscattered photon beam intensities by factors of 1.5--1.8 with the injection of two adjacent laser beams or a higher power laser beam into the storage ring. The maximum energy of the photon beam was also extended from 2.4 GeV to 2.9 GeV with deep-ultraviolet lasers. The upgraded beams have been utilized for hadron photoproduction experiments at the LEPS beamline. Based on the developed methods, we plan the simultaneous injection of four high power laser beams at the LEPS2 beamline, which has been newly constructed at SPring-8. As a simulation result, we expect an order of magnitude higher intensities close to 10$^7$ sec$^{-1}$ and 10$^6$ sec$^{-1}$ for tagged photons up to 2.4 GeV and 2.9 GeV, respectively., 31 pages, 9 figures, Submitted to Nuclear Instruments and Methods in Physics Research Section A on 29 May 2013

The exclusive reaction γp→K(+)π(-)Σ(+) was measured for the first time using linearly polarized photons at beam energies from 1.85 to 2.96 GeV. Angular distributions in the rest frame of the K(+)π(-) system were fitted to extract spin-density matrix elements of the K(*0) decay. The measured parity spin asymmetry shows that natural-parity exchange is dominant in this reaction. This result clearly indicates the need for t-channel exchange of the κ(800) scalar meson.

The exclusive reaction γp→K(+)π(-)Σ(+) was measured for the first time using linearly polarized photons at beam energies from 1.85 to 2.96 GeV. Angular distributions in the rest frame of the K(+)π(-) system were fitted to extract spin-density matrix elements of the K(*0) decay. The measured parity spin asymmetry shows that natural-parity exchange is dominant in this reaction. This result clearly indicates the need for t-channel exchange of the κ(800) scalar meson.

A gas analyzer system has been developed to analyze Hydrogen-Deuteride (HD) gas for producing frozen-spin polarized HD targets, which are used for hadron photoproduction experiments at SPring-8. Small amounts of ortho-H$_{2}$ and para-D$_{2}$ gas mixtures ($\sim$0.01%) in the purified HD gas are a key to realize a frozen-spin polarized target. In order to obtain reliable concentrations of these gas mixtures in the HD gas, we produced a new gas analyzer system combining two independent measurements with the gas chromatography and the QMS. The para-H$_{2}$, ortho-H$_{2}$, HD, and D$_{2}$ are separated using the retention time of the gas chromatography and the mass/charge. It is found that the new gas analyzer system can measure small concentrations of $\sim$0.01% for the otho-H$_2$ and D$_2$ with good S/N ratios., 7 pages, 8 figures

The LEPS/SPring-8 experiment made a comprehensive measurement of the spin-density matrix elements for $\gamma p \to \phi p$, $\gamma d \to \phi p n$ and $\gamma d \to \phi d$ at forward production angles. A linearly polarized photon beam at $E_{\gamma}$=1.6-2.4 GeV was used for the production of $\phi$ mesons. The natural-parity Pomeron exchange processes remains dominant nearthreshold. The unnatural-parity processes of pseudoscalar exchange is visible in the production from nucleons but is greatly reduced in the coherent production from deuterons. There is no strong $E_{\gamma}$-dependence, but some dependence on momentum-transfer. A small but finite value of the spin-density matrix elements reflecting helicity-nonconserving amplitudes in the $t$-channel is observed., Comment: 25 pages, 14 figures

Differential cross sections and photon-beam asymmetries for the $\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\gamma}}p\ensuremath{\rightarrow}{K}^{+}\ensuremath{\Lambda}(1520)$ reaction have been measured with linearly polarized photon beams at energies from the threshold to 2.4 GeV at $0.6l\mathrm{cos} {\ensuremath{\theta}}_{\mathrm{c}.\mathrm{m}.}^{K}l1$. A new bump structure was found at $W\ensuremath{\simeq}2.11\text{ }\text{ }\mathrm{GeV}$ in the cross sections. The bump is not well reproduced by theoretical calculations introducing a nucleon resonance with $J\ensuremath{\le}\frac{3}{2}$. This result suggests that the bump might be produced by a nucleon resonance possibly with $J\ensuremath{\ge}\frac{5}{2}$ or by a new reaction process, for example, an interference effect with the $\ensuremath{\phi}$ photoproduction having a similar bump structure in the cross sections.

Differential cross sections for {eta} photoproduction from protons have been measured at E{sub {gamma}}=1.6-2.4 GeV in the backward direction. A bump structure has been observed above 2.0 GeV in the total energy. No such bump is observed in {eta}{sup '},{omega}, and {pi}{sup 0} photoproductions. It is inferred that this unique structure in {eta} photoproduction is due to a baryon resonance with a large ss component that is strongly coupled to the {eta}N channel.