Search

Joint measurements of complementary polarizations are performed on entangled photon pairs, clarifying the relation between measurement uncertainties and quantum non-locality. Extremely low probabilities indicate that the non-local correlations are close to the Cirel'son bound.

We report the result from a search for charged-current coherent pion production induced by muon neutrinos with a mean energy of 1.3 GeV. The data are collected with a fully active scintillator detector in the K2K long-baseline neutrino oscillation experiment. No evidence for coherent pion production is observed and an upper limit of $0.60 \times 10^{-2}$ is set on the cross section ratio of coherent pion production to the total charged-current interaction at 90% confidence level. This is the first experimental limit for coherent charged pion production in the energy region of a few GeV., 5 pages, 4 figures

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.

To realize optimal simultaneous control of transverse position and momentum, we have constructed a Sagnac interferometer and evaluated the interference between spatial modes with extremely different profiles. The results are consistent with theoretical expectations. © 2019 The Author(s)

To clarify the relation between a Bell’s inequality and measurement uncertainty, we have experimentally introduced joint measurements of two complementary polarizations. Joint statistics can be obtained because measurement uncertainties reduce the observed correlations.

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

Bell's inequalities are defined by sums of correlations involving non-commuting observables in each of the two systems. Violations of Bell's inequalities are only possible because the precision of any joint measurement of these observables will be limited by quantum mechanical uncertainty relations. In this paper we explore the relation between the local measurement uncertainties and the magnitude of the correlations by preparing polarization entangled photon pairs and performing joint measurements of non-commuting polarization components at different uncertainty trade-offs. The change in measurement visibility reveals the existence of a non-trivial balance between the measurement uncertainties where the probabilities of a specific pair of measurement outcomes approaches zero because of the particular combination of enhancement and suppression of the experimentally observed correlations. The occurrence of these high-contrast results shows that the quantum correlations between the photons are close to their maximal value, confirming that the Cirel'son bound of Bell's inequality violations is defined by the minimal uncertainties that limit the precision of joint measurements., Comment: 20 pages, 9 figures

We have experimentally evaluated the non-classical relation between measurement errors in a joint measurement of two non-commuting polarizations by using entangled photon pairs as a probe. The joint measurement was realized by filtering polarization directions that are sensitive to both of the two target polarizations and the same filtering procedures were applied independently to the two photons of an entangled pair. Since the statistically independent measurement errors of two identical measurements performed on entangled pairs will reduce an overall visibility of the correlation by the square of the local visibilities, the squared visibilities of the local measurements can be obtained directly from the measurement data. We apply this method to determine the visibility of the correlation between the products of the two non-commuting polarizations, a characteristic of the measurement errors that can not be obtained locally since there is no self-adjoint operator that describes this product of measurement outcomes as a single photon observable. The experimental results clearly show that the square of the product visibility is negative, indicating the non-classical nature of the statistical relation between the measurement errors of non-commuting polarizations., 9 pages, 4 figures

In order to evaluate a quantum correlation between two measurement errors in a joint measurement, we performed correlation measurements of entangled photon pairs with two identified joint measurements, where two different non-commuting polarizations are jointly measured for each photon. The joint measurements were realized by filtering the polarization oriented the direction, which is halfway in two observables. The experimentally observed correlations corresponded to the ideal correlations expected for the entangled state, except for the correlation between the products of the two non-commuting polarizations. This result exceeds the limits that apply to classical error statistics and suggests that the correlation between the measurement errors in each local measurement is imaginary.

Quantum statistics is defined by Hilbert space products between the eigenstates associated with state preparation and measurement. The same Hilbert space products also describe the dynamics generated by a Hamiltonian when one of the states is an eigenstate of energy E and the other represents an observable B. In this paper, we investigate this relation between the observable time evolution of quantum systems and the coherence of Hilbert space products in detail. It is shown that the times of arrival for a specific value of B observed with states that have finite energy uncertainties can be used to derive the Hilbert space product between eigenstates of energy E and eigenstates of the dynamical variable B. In these Hilbert space products, quantum phases and interference effects appear in the form of an action that relates energy to time in the experimentally observable dynamics of localized states. Quantum effects emerge in the measurement statistics when the precise control of energy in quantum state preparation results in a coherent randomization of the dynamics, such that two different arrival times contribute to the quantum statistics of the same measurement outcome B. The non-classical features associated with quantum interference can thus be explained as a consequence of quantum dynamics and its role in state preparation and measurement, indicating that the apparent randomness of control described by the energy-time uncertainties is not merely a technical problem but rather originates from the fundamental nature of interactions between physical systems., Comment: 23 pages, including 5 figures, improved explanation of the fundamental relation between energy and time and the state-independence of B(t;E) in section II and III

Various benzylic and aliphatic alcohols were smoothly oxidized to the corresponding aromatic aldehydes and ketones as well as aliphatic ketones by treatment with 1-acetoxy-5-nitro-1,2-benziodoxole-3(1H)-one (ANBX), 1-acetoxy-5-bromo-1,2-benziodoxole-3(1H)-one (ABBX), 1-acetoxy-5-chloro-1,2-benziodoxole-3(1H)-one (ACBX), and 1-acetoxy-5-fluoro-1,2-benziodoxole-3(1H)-one (AFBX). These new trivalent iodine compounds were prepared from 5-substituted 2-iodobenzoic acids and meta-chloroperoxybenzoic acid (m-CPBA). ANBX and ABBX were the most effective reagents for this oxidation of alcohols, and this present reaction is very attractive because of the ease of product isolation and the reusability of the reagents.

Various benzylic alcohols and aliphatic secondary alcohols were smoothly oxidized to the corresponding aromatic aldehydes, aromatic ketones, and aliphatic ketones, respectively, with the novel 1-acetoxy-5-nitro-1,2-benziodoxole-3(1H)-one (ANBX) alone, a trivalent iodine prepared from the oxidation of 2-iodo-5-­nitrobenzoic acid with MCPBA. The present reaction is the first ­effective method for the oxidation of alcohols with a trivalent iodine alone under mild reaction conditions.

The oxidation of secondary alcohols and primary alcohols with two novel ion-supported (diacetoxyiodo)benzenes (IS-DIBs) A and B in the presence of a catalytic amount of 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) in dichloromethane at room temperature proceeded efficiently to provide the corresponding ketones and aldehydes, respectively, in good yields. The oxidative reaction of N , N -diisopropylbenzylamines with those IS-DIBs was also carried out to generate the corresponding aromatic aldehydes in good yields. In addition, the Hofmann rearrangement of primary amides in methanol under basic conditions and the oxidative 1,2-rearrangement of propiophenones in trimethyl orthoformate under acidic conditions with those IS-DIBs provided the corresponding methyl carbamates and methyl 2-arylpropanoates, respectively, in good yields. Moreover, treatment of acetophenones with those IS-DIBs in the presence of trifluoromethanesulfonic acid in acetonitrile generated the corresponding 5-aryl-2-methyloxazoles in good yields. In those five reactions, the desired products were obtained in good yields with high purity by simple extraction of the reaction mixture with diethyl ether and subsequent removal of the solvent from the extract. Moreover, ion-supported iodobenzenes, which were the co-products derived from IS-DIBs in the present oxidative reactions, were recovered in good yields and could be re-oxidized to IS-DIBs A and B for reuse in the same oxidative reactions.

The technique of photon counting is widely used for various fields and also applicable to a high-sensitivity detection of luminescence. Thanks to recent development of single photon detectors with avalanche photodiodes (APDs), the photon counting system with an optical fiber has become powerful for a detection of bioluminescence at an optical fiber end, because it allows us to fully use the merits of compactness, simple operation, highly quantum efficiency of the APD detectors. This optical fiber-based system also has a possibility of improving the sensitivity to a local detection of Adenosine triphosphate (ATP) by high-sensitivity detection of the bioluminescence. In this chapter, we are introducing a basic concept of the optical fiber-based system and explaining how to construct and use this system.

The technique of photon counting is widely used for various fields and also applicable to a high-sensitivity detection of luminescence. Thanks to recent development of single photon detectors with avalanche photodiodes (APDs), the photon counting system with an optical fiber has become powerful for a detection of bioluminescence at an optical fiber end, because it allows us to fully use the merits of compactness, simple operation, highly quantum efficiency of the APD detectors. This optical fiber-based system also has a possibility of improving the sensitivity to a local detection of Adenosine triphosphate (ATP) by high-sensitivity detection of the bioluminescence. In this chapter, we are introducing a basic concept of the optical fiber-based system and explaining how to construct and use this system.

One of the most difficult problems in quantum mechanics is the analysis of the measurement processes. In this paper, we point out that many of these difficulties originate from the different roles of measurement outcomes and observable quantities, which cannot simply be identified with each other. Our analysis shows that the Hilbert space formalism itself describes a fundamental separation between quantitative properties and qualitative outcomes that needs to be taken into account in an objective description of quantum measurements. We derive fundamental relations between the statistics of measurement outcomes and the values of physical quantities that explain how the objective properties of a quantum system appear in the context of different measurement interactions. Our results indicate that non-classical correlations can be understood in terms of the actual role of physical properties as quantifiable causes of the external effects observed in a quantum measurement., Comment: 11 pages, updated references and clarification of weak value reference below Eq.(12)

Various [(diacetoxy)iodo]arenes bearing 4-methylphenyl, phenyl, 4-nitrophenyl, 3-nitrophenyl, 4-cyanophenyl, 4-bromophenyl, 4-methoxycarbonyphenyl, 3,5-bis(trifluoromethyl)phenyl, and 4-(N,N,N-trimethylammonium)methylphenyl groups were efficiently prepared by the treatment of iodoarenes with m-chloroperoxybenzoic acid in acetic acid. The great advantage of the present method is the easy preparation and isolation of [(diacetoxy)-­iodo]arenes bearing electron-withdrawing groups, such as 4-nitro, 4-cyano, 4-methoxycarbonyl, and 3,5-bis(trifluoromethyl) groups, on the aromatic ring.

The oxidation of secondary alcohols and primary alcohols with novel ion-supported (diacetoxyiodo)benzenes (IS-DIB) in the presence of a catalytic amount of 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO) in dichloromethane at room temperature proceeded efficiently to provide the corresponding ketones and aldehydes, respectively, in good yields with high purity. Isolation of the product was easily accomplished by simple diethyl ether extraction of the reaction mixture and subsequent removal of the solvent from the extract. Moreover, ion-supported iodobenzenes, which were co-products derived from IS-DIB in the present oxidation, were recovered in good yields and could be re-oxidized to IS-DIB for reuse in the same oxidation.

We investigated the sensitivity of ATP detection based on bioluminescence at an optical fiber end where luciferase molecules were immobilized via silica-binding protein molecules. Luminescence was detected by an avalanche photodiode (APD), with coupling optics to make full use of the merits of compactness, high quantum efficiency, and low noise of the APD. The core diameter and the numerical aperture of the optical fiber, as well as the design of the coupling optics, were optimized so as to realize high photon-collection efficiency. A detection limit of about 10−10 M was obtained, which corresponds to 10−15 mol of ATP. A rough estimation shows that the photon count rate is still two orders of magnitude lower than that limited by diffusion or reaction processes, implying a possibility of further improvement of the sensitivity. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 92(9): 53–59, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10054

In general, it is difficult to evaluate measurement errors when the initial and final conditions of the measurement make it impossible to identify the correct value of the target observable. Ozawa proposed a solution based on the operator algebra of observables which has recently been used in experiments investigating the error-disturbance trade-off of quantum measurements. Importantly, this solution makes surprisingly detailed statements about the relations between measurement outcomes and the unknown target observable. In the present paper, we investigate this relation by performing a sequence of two measurements on the polarization of a photon, so that the first measurement commutes with the target observable and the second measurement is sensitive to a complementary observable. While the initial measurement can be evaluated using classical statistics, the second measurement introduces the effects of quantum correlations between the non-commuting physical properties. By varying the resolution of the initial measurement, we can change the relative contribution of the non-classical correlations and identify their role in the evaluation of the quantum measurement. It is shown that the most striking deviation from classical expectations is obtained at the transition between weak and strong measurements, where the competition between different statistical effects results in measurement values well outside the range of possible eigenvalues., 11 pages, 6 figures, small corrections to setup figure

Quantum information science is based on the superposition principle and the non-local quantum correlation of quantum states. These non-classical properties are still mysterious and inadequately understood as physical phenomena. The biggest reason to un-resolving such problems is that we can directly not get all bare information of the quantum states since an action by any measurement absolutely changes the quantum states. Recently, we realized a variable strength measurement of photon polarization, which is capable of controlling the measurement strength from zero (no measurement) to fully projection (completely destructive measurement). This apparatus makes it possible to perform a sequential measurement of two non-commuting observables with an error and the back-action effects produced by the measurement, which never gives exact values simultaneously. We investigated the role of measurement uncertainties of the first variable strength measurement. The experimentally-obtained joint probabilities can be recognized as statistical mixture obtained by random polarization flips arising the measurement uncertainties from an intrinsic joint probability distribution. This natural assumption provided a removal of the back-action effect from the experimental probabilities and the obtained intrinsic probabilities resulted in negative. This analysis also shows how the negative probabilities are converted to observable positive statistics by variable combinations of resolution and back-action uncertainties.

Measurement error can be evaluated using the concepts introduced by Ozawa in 2003. Importantly, this evaluation takes into account the non-classical effects of quantum correlations. We investigate this effect by using a sequence of non-commuting measurements of photon polarization with a variable measurement resolution for the intermediate measurement. It is shown that quantum correlations between the initial and the final measurement outcomes result in a significant reduction of the measurement errors for the target observable, even though the final measurement is not sensitive to the polarization component of interest.

A new result on the deflection of 150 MeV electron beams with using the 〈1 0 0〉 axis of a silicon crystal is presented. The channeling effect of electrons passed through the crystal was clearly seen. We also studied dependence of the deflection on the beam divergence. The simulation qualitatively agreed with the experimental data.

We present measurements of nu_mu disappearance in K2K, the KEK to Kamioka long-baseline neutrino oscillation experiment. One hundred and twelve beam-originated neutrino events are observed in the fiducial volume of Super-Kamiokande with an expectation of 158.1^{+9.2}_{-8.6} events without oscillation. A distortion of the energy spectrum is also seen in 58 single-ring muon-like events with reconstructed energies. The probability that the observations are explained by the expectation for no neutrino oscillation is 0.0015% (4.3sigma). In a two flavor oscillation scenario, the allowed Delta m^2 region at sin^2(2theta) is between 1.9 and 3.5 x 10^{-3} eV^2 at the 90% C.L. with a best-fit value of 2.8 x 10^{-3} eV^2., Comment: 40 pages, 48 figures

We observed photon generation in the second harmonic region in collisions of 10 keV free electrons and the intense laser beam with the peak intensity of 4.0 × 10 15 W / cm 2 . Observed photon yield was 3 orders of magnitude higher than expectation from the nonlinear Compton scattering. The observation indicates necessity of further investigation for the interaction between the intense laser field and the low energy electron beam.

We have carried out detailed systematic studies of relaxation effects, which contribute to a significant improvement in proton polarization in a single crystal of naphthalene doped with pentacene. The experiments have been performed in a magnetic field of 3 kG at room temperature or at 77 K and with a pulsed dye laser or a pulsed N 2 laser. We have found that a relaxation rate in the presence of irradiation with visible light (λ=595 nm) is much smaller than that with ultraviolet light (λ=337 nm) at room temperature, although the absorption rate of visible light is much larger than that of ultraviolet light. By cooling the crystal, the slow motion of the naphthalene molecules, which is a dominant relaxation process, can be suppressed. Surprisingly, we have found that the relaxation time at 77 K in the presence of the dye laser becomes long, but still depends on the laser power. Our investigation has also indicated that both the longer relaxation time and the irradiation with the dye laser lead to a great i...

We have carried out the experiments for polarizing protons in single crystals of p-terphenyl doped with 0.1 mol% pentacene. The experiments have been performed in a magnetic field of 3 kG at room temperature or at 77 K. We obtained the polarization of 1.3% for protons in bulk at room temperature by using a pulsed dye-laser with the wavelength of 590 nm, the average power of 150 mW, and the repetition rate of 50 Hz. The polarization at 77 K reached 18% by irradiation with the dye-laser of 500 mW, 50 Hz and the same wavelength. The polarization of protons was measured by the neutron transmission method also. The result was consistent with that measured by the nuclear magnetic resonance.

Protons in single crystals of naphthalene doped with pentacene and p-terphenyl doped with pentacene have been polarized up to 32% and 18%, respectively. Such polarization has been achieved at liquid nitrogen temperature in a magnetic field of 3 kG by means of microwave-induced optical nuclear polarization. We also measured the polarization by the neutron transmission method. The relaxation time at 77 K in 7 G was found to be about 3 h and the enhancement of the obtained polarization compared with thermal polarization reached 8×104. This method is applicable to neutron experiments.

We have performed a series of experiments to observe 11 Stark-induced E1 transitions from the 15650.55 cm-1 level to higher levels with odd parity in samarium (Sm) with optical double-resonance technique. Five Stark-induced E1 transition to the 28233.08, 28613.22, 28913.97, 29041.31 and 29130.03 cm-1 levels have been observed. In order to investigate the contributors to the Stark-induced E1 transition, we have measured scalar and tensor polarizabilities for the observed Stark-induced E1 transitions. Clear Stark splittings were observed for the levels 28233.08 and 28613.22 cm-1, and their tensor polarizabilities were determined for each isotope. Scalar polarizabilities were determined for the 28233.08, 28613.22, 28913.97 and 29130.03 cm-1 levels for the first time. Among them, scalar polarizability for the 28233.08 cm-1 level was the largest in magnitude and was 3.60(10) x 103 kHz/(kV/cm)2 for $\hspace{0.1em}^{152}$ Sm. We noticed that both scalar and tensor polarizabilities of the 28233.08 cm-1 level depend on the isotope; the difference of magnitude of the scalar and tensor polarizabilities between $\hspace{0.1em}^{144}$ Sm and $\hspace{0.1em}^{154}$ Sm were remarkably large and were about 10 and 6 percent, respectively.

The Stark-induced electric dipole ( E 1) transition for a high-lying odd-parity level in atomic samarium (Sm) was observed with an optical double-resonance technique as a preliminary study for measuring parity nonconservation (PNC). While a pump laser was locked to an E 1 transition from the 0-cm -1 to 15650.55-cm -1 levels, a probe laser was tuned to the parity forbidden transitions under static electric field. For the probe transition from the 15650.55-cm -1 to 28233.08-cm -1 levels, we have observed the Stark-induced E 1 transition. In order to investigate the contribution of the 28233.08-cm -1 level to the Stark-induced E 1 transition, the tensor polarizability was measured. We have found that the observed Stark-induced E 1 transition is anomalously strong compared with the one estimated from α 2 and an E 1 transition measured as a reference. The transition is one of candidates for improving the precision of the PNC measurements.

The violations of Leggett-Garg inequalities can be confirmed independent of strength of the intermediate measurement, if we take into account the measurement uncertainties of a sequential measurement. We experimentally confirm the negative joint probabilities corresponding to the Leggett-Garg inequalities violations for a wide range of measurement uncertainties using a statistical model to describe the effects of measurement resolution and back-action.

The excitation energies and hyper-fine structure constants of the low-lying levels of Sm atom are calculated using the multi-configuration Dirac-Fock (MCDF) method. The results show that the excitation energies of the ground state multiplets can be calculated accurately using a small orbital set but the higher levels need larger orbital sets. Similar inference can also be drawn from the discrepancy between the calculated values of the hyper-fine constants and the experimental data. A sequence of MCDF calculation demonstrates the effect of the MCDF potential on the orbitals. Among the rare earth atoms Sm is a promising candidate for discrete symmetry violation experiments in atoms. This makes accurate theoretical calculations necessary since parameters in particle physics can be derived by combining the experimental results with the theoretical results. And these could be a probe for the physics beyond the standard model.

We have performed an experiment of positron generation using a crystal target at an electron/positron linac at KEK. The target consists of a tungsten crystal to emit photons and an amorphous tungsten for pair creation, whose thicknesses are 0.5 and 2.0 radiation length, respectively. When the 〈1 1 1〉 crystal axis is oriented parallel to the 3 GeV incident electron beam, the positron yield is enhanced by 40% compared to values for the disoriented crystal. No effect of injecting intense ultra-short electron bunches on the crystalline structure is observed. The crystal orientation dependence of the positron yield as well as the enhancement factor can be explained by a simulation assuming a coherent bremsstrahlung process of the electron in the crystal.

We constructed an experimental system to observe nonlinear effects in the Compton scattering. The electron beam is supplied by an electron gun and a photon beam comes from a Table-top Ten-Tera-watt Ten-Hz Tunable Ti:sapphire laser system, named T6-laser, of Institute of Laser Engineering, Osaka University. As a test experiment, we measured the Compton scattering in a linear regime and had a reasonable agreement with simulation.

We have developed a large-area 10 B -loaded liquid scintillation detector for parity-violation studies in neutron resonances with high instantaneous neutron fluxes from the LANSCE short-pulse spallation source. The detector has an efficiency of 95%, 85% and 71% at neutron energies of 10, 100 and 1000 eV, respectively. The neutron mean capture time in the detector is (416±5) ns . We describe the detector and the current-mode signal processing system, that can handle neutron rates up to 500 MHz.

The relative cross section of pair creation from a silicon single crystal has been measured with a bremsstrahlung beam from 350 MeV electrons. A clear enhancement was observed above 230 MeV as expected from the theory based on the type-B coherent effect.

Dynamic nuclear polarization (DNP) has been performed in a magnetic field of 2.35 T at a temperature below 0.3 K in crystals of Nd 3+ : LaAlO 3 . A Q-meter NMR-system was used to measure the polarization of the 27Al and 139La nuclei and allowed to characterize the quality of the crystals. The 139La polarizations of +47.5% and −56.5% achieved represent an important step in the development of a polarized 139La target for a test of time reversal invariance in low-energy neutron reactions.

Protons in naphthalene and p-terphenyl doped with pentacene have been polarized up to 32% and 18%, respectively, at liquid nitrogen temperature in a magnetic field of 0.3 T by means of microwave-induced optical nuclear polarization. The polarization was measured by nuclear magnetic resonance as well as by the neutron transmission method. The relaxation time of the proton polarization at 0.0007 T and 77 K was found to be almost 3 h and the polarization enhancement reached a record value of 8 3 10 4 . The usefulness of the method in many areas of physics and chemistry is discussed. PACS numbers: 76.70.Fz, 24.70. + s, 29.25.Pj

Hyperfine structures, isotope shifts and Stark effects of seven near-infrared transitions in Sm I are investigated by means of atomic-beam laser spectroscopy with fluorescence detection. E 1 transi...

A new search has been performed for parity violation in the compound nuclear states of ${}^{94}\mathrm{Nb}$ by measuring the helicity dependence of the neutron total cross section. Transmission measurements on a thick niobium target were performed by the time-of-flight method at the Manuel Lujan Neutron Scattering Center with a longitudinally polarized neutron beam in the energy range 32 to 1000 eV. A total of 18 p-wave resonances in ${}^{93}\mathrm{Nb}$ were studied with none exhibiting a statistically significant parity-violating longitudinal asymmetry. An upper limit of $1.0\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$ eV (95% confidence level) was obtained for the weak spreading width ${\ensuremath{\Gamma}}_{w}$ in ${}^{93}\mathrm{Nb}.$

Parity nonconservation (PNC) was studied in {ital p}-wave resonances in Ag by measuring the helicity dependence of the neutron total cross section. Transmission measurements on natural Ag were performed in the energy range 32 to 422 eV with the time-of-flight method at the Manuel Lujan Neutron Scattering Center at Los Alamos National Laboratory. A total of 15 {ital p}-wave neutron resonances were studied in {sup 107}Ag and nine {ital p}-wave resonances in {sup 109}Ag. Statistically significant asymmetries were observed for eight resonances in {sup 107}Ag and for four resonances in {sup 109}Ag. An analysis treating the PNC matrix elements as random variables yields a weak spreading width of {Gamma}{sub w}=(2.67{sub {minus}1.21}{sup +2.65}){times}10{sup {minus}7} eV for {sup 107}Ag and {Gamma}{sub w}=(1.30{sub {minus}0.74}{sup +2.49}){times}10{sup {minus}7} eV for {sup 109}Ag. thinsp {copyright} {ital 1999} {ital The American Physical Society}

Enhanced production of ΛΛ pairs, above levels predicted by a two-step process model, has been observed near threshold (in the mass range 2.23-2.26 GeV/c2) in the 12C(K−,K+) reaction at 1.66 GeV/c using a scintillating fiber target. The differential cross section for ΛΛ production in the momentum region 0.95≤pK+≤1.3 GeV/c averaged over the range 2.3o≤θK+≤14.7o was found to be 7.6±1.3 ±0.9 μ b/sr, and that for the enhancement was found to be approximately 3 μ b/sr.

Cascade hypernuclei have been studied in the ${(K}^{\ensuremath{-}}{,K}^{+})$ reaction on a scintillating fiber target. The experimental result is compared with a theoretical calculation in order to extract information concerning the ${\ensuremath{\Xi}}^{\ensuremath{-}}$ nucleus potential.

Hyperon-proton scattering is being studied at KEK in order to obtain a better understanding standing of the baryon-baryon interaction. A scintilating fiber (SCIFI) block detector has been used as a production target of hyperons as well as a target for hyperon scattering on hydrogen. The pilot experiment (E251) for Σ + p scattering has been completed, and the next experiment (E289) for Σ + p, Σ − p and Λp channels has finished its data taking and is now uder analysis.

Enhanced production of ΛΛ pairs, above the prediction of a two-step process model, is observed near threshold (around the masses of 2.23 – 2.26 GeV/c2) in the12C(K−,K+) reaction at PK− = 1.66GeV/c using a scintillating fiber target. The differential cross section for the ΛΛ production averaged over 2.3° ≤ $$K + ≤ 14.7° in the momentum region 0.95 ≤ pK + ≤ 1.3GeV/c was found to be 7.6 ± 1.3 μb/sr, and that for the enhancement approximately 3 μb/sr.