Search

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.

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

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

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)

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

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

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

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.

The double strangeness exchange reaction ( K − , K + ) is investigated with respect to the sub-threshold production of scalar and vector mesons ( f 0 / a 0 / φ ) decaying into K + K − and the two-step processes induced by intermediate mesons and Ξ − hyperons at p k − = 1.66 GeV/ c using a scintillating fiber active target. The differential cross section ( 〈 dσ dΩ L 〉) averaged over the angular interval (2.3° ⩽ θ K + L ⩽ 14.7°) for the sub-threshold f 0 / a 0 / φ meson production with the K + K − decay is 11 ± 6 μ b/sr at 0.6 ⩽ p K 1 c . The present result differs significantly from the theoretical calculation which predicts the contribution of the f 0 / a 0 / φ meson production to be predominant in the ( K − , K + ) reaction below p K + = 0.95 GeV/ c . We found a sizable contribution from two-step ( K − , K + processes, characterized by production of two S = −1 hyperons, consistent with the result of the intra-nuclear cascade (INC) model calculation with respect to the meson-induced hyperon (or hyperon resonance) pair production in the momentum region 0.6 ⩽ p K + c . The observed enhancement of the cross section for the two-step ΛΛ production beyond the prediction of the INC model at p K + ⋍ 1.1 GeV /c could be due to the Ξ − p → ΛΛ reaction in 12 C.

Parity-violating spin rotation of neutrons in a 139La target was observed in the vicinity of the 0.734 eV p-wave resonance. The measured angle of rotation, φpnc(E), shows a large enhancement around the resonance. The data are fitted with a theoretical function from the s-p mixing models of the parity-violation enhancement, yielding a parity mixing matrix element xW = 1.04 ± 0.40 meV which is in agreement with those previously obtained from the longitudinal asymmetry in the p-wave resonance cross section.

We describe an apparatus for studies of parity violation in neutron-nucleus scattering. This experiment requires longitudinally polarized neutrons from the Los Alamos Neutron Scattering Center over the energy range from 1 to 1000 eV, the ability to reverse the neutron spin without otherwise affecting the apparatus, the ability to detect neutrons at rates up to 500 MHz and an appropriate data acquisition system. We will discuss the neutron polarizer, fast neutron spin reverser, detector for transmitted neutrons and high rate data acquisition system.

We have studied ( K − , K + ) reactions at P K − = 1.66 GeV/c by using a newly developed active target made of plastic scintillating fibers. The H dibaryon ( S = −2, I ( J π ) = 0(0 + )) has been searched for through the direct process, K − + C → K + + H + X , by the analysis of the K + momentum spectrum with the help of visual data of the scintillating fiber target. No evidence for the H production was observed. Upper limits for the differential cross section for the H production in the forward direction of the K + is 0.04–0.6 μb/sr at the 90% confidence level for the H mass range from 1850 to 2215 MeV/c 2 .

Interpretations of an experiment on the back-action in a weak measurement in [M. Iinuma et al., New J. Phys. vol.13 (2011), 033041] are revisited. We show two different but essentially equivalent interpretations for this experiment along the original scenario of weak measurements proposed by Aharonov, Albert, and Vaidman. To do this, we introduce the notion of extended weak values which is associated not only with the states of the system but also the state of the measuring device. We also evaluate fluctuations in this experiment and found that an optimal measurement strength exists for a fixed polarization angle prepared as an initial state, at which fluctuations in measurement results vanish. The consistency of this evaluation with the experimental results is discussed., Comment: 14 pages, 1 figure (v1); 8 pages, 1 figure, the style is changed. minor revision of Introduction, Summary and Discussion (v2); minor revision of Summary and discussions (v3); Minor revision of introduction and summary and discussion. Typos are corrected. Accepted for publication to Physical Review A

A sequential measurement of two non-commuting quantum observables results in a joint probability distribution for all output combinations that can be explained in terms of an initial joint quasi-probability of the non-commuting observables, modified by the resolution errors and back-action of the initial measurement. Here, we show that the error statistics of a sequential measurement of photon polarization performed at different measurement strengths can be described consistently by an imaginary correlation between the statistics of resolution and back-action. The experimental setup was designed to realize variable strength measurements with well-controlled imaginary correlation between the statistical errors caused by the initial measurement of diagonal polarizations, followed by a precise measurement of the horizontal/vertical polarization. We perform the experimental characterization of an elliptically polarized input state and show that the same complex joint probability distribution is obtained at any measurement strength., 20 pages, 7 figures, update introduction, add comment after Eq.(12)

In biological studies, the luminescence from fluorescent proteins or luminescent enzymes is widely used for monitoring a change of environment at a cell. Biomolecules used for this probing, such as Green Fluorescence Protein(GFP) or luciferase molecules can respond to the existence of specific molecules or ions and subsequently emit a photon. The detection of a specific molecule can then be confirmed by detecting the emitted photons efficiently with a photon detector. A highly efficient detection of the luminescence is normally essential to a high sensitivity to the specific molecules or ions. An improvement of the sensitivity can upgrade the capability of detection in a low concentration of sample solution. Therefore, there are many efforts to improve the efficiency of the collection of emitted photons and of the optical coupling to the photon detector (Yotter, 2004).

In this paper we report on the measurement of the rate of inclusive $\pi^0$ production induced by charged-current neutrino interactions in a C$_8$H$_8$ target at a mean energy of 1.3 GeV in the K2K near detector. Out of a sample of 11,606 charged current neutrino interactions, we select 479 $\pi^0$ events with two reconstructed photons. We find that the cross section for the inclusive $\pi^0$ production relative to the charged-current quasi-elastic cross section is $$\frac{\sigma_{CC\pi^0}}{\sigma_{CCQE}}=0.426\pm0.032(stat.)\pm0.035(syst.)$$ The energy dependent cross section ratio is also measured. The results are consistent with previous experiments for exclusive channels on different targets., Comment: 18 pages, 11 figures, submitted to PRD

The essential feature of weak measurements on quantum systems is the reduction of measurement back-action to negligible levels. To observe the non-classical features of weak measurements, it is therefore more important to avoid additional back-action errors than it is to avoid errors in the actual measurement outcome. In this paper, it is shown how an optical weak measurement of diagonal (PM) polarization can be realized by path interference between the horizontal (H) and vertical (V) polarization components of the input beam. The measurement strength can then be controlled by rotating the H and V polarizations towards each other. This well-controlled operation effectively generates the back-action without additional decoherence, while the visibility of the interference between the two beams only limits the measurement resolution. As the experimental results confirm, we can obtain extremely high weak values, even at rather low visibilities. Our method therefore provides a realization of weak measurements that is extremely robust against experimental imperfections., 11 pages, 3 figures

Spatial qudit states can be realized by using multi-slits to discretize the transverse momentum of a photon. The merit of this kind of spatial qudit states is that the implementation of higher dimensional qudits is relatively easy. As we have recently shown, the quantum states of these spatial qudits can be analyzed by scanning a single interference pattern. This method of single scan tomography can also be applied at higher dimensions, but the reconstruction becomes more sensitive to smaller details of the scanned patterns as the dimensions increase. In this paper, we investigate the effect of finite measurement resolution on the single scan tomography of spatial qutrits. Realistic measurement operators describing the spatial resolution of the measurement are introduced and the corresponding pattern functions for quantum state reconstruction are derived. We use the pattern functions to analyze experimental results for entangled pairs of spatial qutrits generated by spontaneous parametric down-conversion (SPDC). It is shown that a reliable reconstruction of the quantum state can be achieved with finite measurement resolution if this limitation of the measurement is included in the pattern functions of single scan tomography., 15 pages, including 8 figures

The atmospheric neutrino background for proton decay via p→e + π 0 in ring imaging water Cherenkov detectors is studied with an artificial accelerator neutrino beam for the first time. In total, 3.14 × 10 5 neutrino events corresponding to about 10 megaton-years of atmospheric neutrino interactions were collected by a 1000 ton water Cherenkov detector (KT). The KT charged-current single π 0 production data are well reproduced by simulation programs of neutrino and secondary hadronic interactions used in the Super-Kamiokande (SK) proton decay search. The obtained p→ e + π 0 background rate by the KT data for SK from the atmospheric neutrinos whose energies are below 3 GeV is 1.63 +0.42 -0.33 (stat) +0.45 -0.51 (syst)(megaton-year) -1 . This result is also relevant to possible future, megaton-scale water Cherenkov detectors.

We present an experimental study of the non-classical correlations of a pair of spatial qubits formed by passing two down-converted photons through a pair of double slits. After confirming the entanglement generated in our setup by quantum tomography using separate measurements of the slit images and the interference patterns, we show that the complete Hilbert space of the spatial qubits can be accessed by measurements performed in a single plane between the image plane and the focal plane of a lens. Specifically, it is possible to obtain both the which-path and the interference information needed for quantum tomography in a single scan of the transversal distribution of photon coincidences. Since this method can easily be extended to multi-dimensional systems, it may be a valuable tool in the application of spatial qudits to quantum information processes., Comment: 19 pages, including 10 figures and 2 tables

We performed an improved search for {nu}{sub {mu}}{yields}{nu}{sub e} oscillation with the KEK to Kamioka (K2K) long-baseline neutrino oscillation experiment, using the full data sample of 9.2x10{sup 19} protons on target. No evidence for a {nu}{sub e} appearance signal was found, and we set bounds on the {nu}{sub {mu}}{yields}{nu}{sub e} oscillation parameters. At {delta}m{sup 2}=2.8x10{sup -3} eV{sup 2}, the best-fit value of the K2K {nu}{sub {mu}} disappearance analysis, we set an upper limit of sin{sup 2}2{theta}{sub {mu}}{sub e}

In this paper we report cross-section measurements for $\Xi^-p$ elastic and inelastic scatterings at low energy using a scintillating fiber active target. Upper limit on the total cross-section for the elastic scattering was found to be 24 mb at 90% confidence level, and the total cross section for the $\Xi^-p\to\Lambda\Lambda$ reaction was found to be $4.3^{+6.3}_{-2.7}$ mb. We compare the results with currently competing theoretical estimates., Comment: 9 pages

A new near detector for the K2K long baseline neutrino experiment, the SciBar, was constructed and started data taking to study neutrino interactions. In K2K, neutrino oscillation is studied by comparing the number of neutrino interactions and energy spectrum between near and far detectors. In order to study neutrino oscillations more precisely, it is necessary to improve the measurement of neutrino spectrum and interactions below 1 GeV, where the latest K2K results suggest maximum oscillation. For that purpose, SciBar is designed to be fully active with fine segmentation. We present the design and basic performance. All detector components have been working as expected. Also presented are the measurements of charged current interactions which are used in the latest K2K oscillation analysis

We have measured the collisional self-broadening of the cesium 6S1/2→5D3/2 electric quadrupole sE2d transition at 689 nm for temperatures from 220 to 370 °C, corresponding to cesium number densities from 331015 to 1.531017 cm−3. This E2 transition may have utility for studies of atomic parity nonconservation (PNC), and the collisional self-broadening represents an important systematic effect which must be understood for an accurate measurement of PNC. We find a value for this broadening of 1.32±0.06310−8 cm3 s−1, which is consistent with what would be expected for a quadrupole-quadrupole resonance interaction. To the best of our knowledge, no quantitative measurement of the self-broadening of an atomic E2 transition has been reported previously in the literature.

We present results for muon neutrino oscillation in the KEK to Kamioka (K2K) long-baseline neutrino oscillation experiment. K2K uses an accelerator-produced muon neutrino beam with a mean energy of 1.3 GeV directed at the Super-Kamiokande detector. We observed the energy dependent disappearance of muon neutrino, which we presume have oscillated to tau neutrino. The probability that we would observe these results if there is no neutrino oscillation is 0.0050% (4.0 sigma)., Comment: 5 pages, 4 figures

We have measured the hyperfine splitting and level isotope shifts (LIS) of the (6s6p{sup 2}) {sup 4}P{sub 1/2} level of {sup 205}Tl and {sup 203}Tl using laser absorption spectroscopy in a thallium oven near 1373 K. We determine that the hyperfine splitting between the F=1 and 0 levels of the {sup 4}P{sub 1/2} state in {sup 205}Tl is 75.179{+-}0.087 GHz. The F=0 LIS is -7.333{+-}0.025 GHz and the F=1 LIS is -6.500{+-}0.030 GHz, with the {sup 205}Tl level below the {sup 203}Tl level in both cases. We use our results together with other data to analyze the configuration mixing of the {sup 4}P{sub 1/2} state with the nearby (6s{sup 2}10s) {sup 2}S{sub 1/2} state. The mixing inferred from the hyperfine results is consistent with that inferred from the isotope shift results.

The parity-violating longitudinal asymmetry of the neutron scattering cross section has been measured for thorium in the off-resonance energy intervals from 30 to 300 eV. The observed result of $(0.5\ifmmode\pm\else\textpm\fi{}1.6)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ is compared with theoretical predictions.

The analysis of parity nonconservation (PNC) measurements performed on {sup 232}Th by the TRIPLE Collaboration has been extended to include the neutron energy range of 250 to 1900 eV. Below 250 eV all ten statistically significant parity violations have the same sign. However, at higher energies PNC effects of both signs were observed in the transmission of longitudinally polarized neutrons through a thick thorium target. Although the limited experimental energy resolution precluded analysis in terms of the longitudinal asymmetry, parity violations were observed and the cross section differences for positive and negative neutron helicities were obtained. For comparison, a similar analysis was performed on the data below 250 eV, for which longitudinal asymmetries were obtained previously. For energies below 250 eV, the p-wave neutron strength functions for the J=1/2 and J=3/2 states were extracted: S{sub 1/2}{sup 1}=(1.68{+-}0.61)x10{sup -4} and S{sub 3/2}{sup 1}=(0.75{+-}0.18)x10{sup -4}. The data provide constraints on the properties of local doorway states proposed to explain the PNC sign effect in thorium. (c) 2000 The American Physical Society.

Parity nonconservation was studied for 23 p-wave resonances in 113Cd up to En = 500 eV at the LANSCE pulsed neutron source using a longitudinally polarized neutron beam and the time-of-flight method. The helicity dependence of the total neutron capture cross section was measured with an enriched 113Cd target and with a target of natural cadmium. Parity violating effects were observed for several resonances in 113Cd and 111Cd. A root-mean-square value of the parity nonconserving matrix element MJ=1 = 2.9+1.3-0.9 meV was obtained for the spin J=1 levels in the compound nucleus 114Cd. This result from the 3p-peak region of the neutron strength function is compared with the parity violation results for nuclei from the 4p-peak region.

Parity nonconservation (PNC) was measured for 24 p-wave resonances from 8 to 300 eV in 232Th by measuring the helicity dependence of the total neutron cross section for epithermal neutrons with an improved experimental system. Ten resonances show statistically significant parity violation. For these ten resonances the analyzing powers are all positive, thus confirming the previously observed sign correlation. The data are fit to the sum of two terms, a constant asymmetry and a fluctuating asymmetry. With this ansatz the root-mean-square PNC matrix element M=1.12 meV, which corresponds to a weak spreading widthΓw=4.7×10-7 eV. For the neighboring nuclide 238U there is no constant offset, suggesting that the sign correlation is specific to 232Th. Disciplines Atomic, Molecular and Optical Physics | Physics Authors Sharon L. Stephenson, J D. Bowman, Bret E. Crawford, P P J. Delheij, C M. Frankle, M IInuma, J N. Knudsen, L Y. Lowie, A Masaike, Y Matsuda, G E. Mitchell, S I. Penttila, H Postma, N R. Roberson, S J. Seestrom, E I. Sharapov, Y-F Yen, and V W. Yuan This article is available at The Cupola: Scholarship at Gettysburg College: http://cupola.gettysburg.edu/physfac/20 Parity nonconservation in neutron resonances in Th S. L. Stephenson,* J. D. Bowman, B. E. Crawford, P. P. J. Delheij, C. M. Frankle, M. Iinuma, J. N. Knudson, L. Y. Lowie, A. Masaike, Y. Matsuda, G. E. Mitchell, S. I. Penttila, H. Postma, N. R. Roberson, S. J. Seestrom, E. I. Sharapov, Y.-F. Yen, and V. W. Yuan North Carolina State University, Raleigh, North Carolina 27695-8202 and Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708-0308 Los Alamos National Laboratory, Los Alamos, New Mexico 87545 Duke University, Durham, North Carolina 27708 and Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708-0308 TRIUMF, Vancouver, British Columbia, Canada V6T 2A3 Department of Physics, Kyoto University, Kyoto 606-8502, Japan University of Technology, Delft, 2600 GA, The Netherlands Joint Institute for Nuclear Research, 141980 Dubna, Russia ~Received 6 April 1998! Parity nonconservation ~PNC! was measured for 24 p-wave resonances from 8 to 300 eV in Th by measuring the helicity dependence of the total neutron cross section for epithermal neutrons with an improved experimental system. Ten resonances show statistically significant parity violation. For these ten resonances the analyzing powers are all positive, thus confirming the previously observed sign correlation. The data are fit to the sum of two terms, a constant asymmetry and a fluctuating asymmetry. With this ansatz the root-meansquare PNC matrix element M51.12 meV, which corresponds to a weak spreading width Gw54.7310 27 eV. For the neighboring nuclide U there is no constant offset, suggesting that the sign correlation is specific to Th. @S0556-2813~98!03608-5# PACS number~s!: 25.40.Ny, 24.80.1y, 11.30.Er, 27.90.1b

Measurements have been performed on the helicity dependence of the neutron resonance cross section for many nuclei by our TRIPLE Collaboration. A large number of parity violations are observed. Generic enhancements amplify the signal for symmetry breaking and the stochastic properties of the compound nucleus permit the strength of the symmetry-breaking interaction to be determined without knowledge of the wave functions of individual states. A total of 15 nuclei have been analyzed with this statistical approach. The results are summarized.

The parity and time‐reversal symmetries can be studied in neutron‐nucleus interactions. Parity non‐conserving asymmetries have been observed for many p‐wave resonances in a compound nucleus and measurements were performed on several nuclei in the mass region of A∼100 and A∼230. The statistical model of the compound nucleus provides a theoretical basis for extracting mean‐squared matrix elements from the experimental asymmetry data, and for interpreting the mean‐squared matrix elements. The constraints on the weak meson‐exchange couplings calculated from the compound‐nucleus asymmetry data agree qualitatively with the results from few‐body and light‐nuclei experiments. The tests of time‐reversal invariance in various experiments using thermal, epithermal, and MeV neutrons are being developed.

Quantum mechanics violates Leggett-Garg inequalities because the operator formalism predicts correlations between different spin components that would correspond to negative joint probabilities for the outcomes of joint measurements. However, the uncertainty principle ensures that such joint measurements cannot be implemented without errors. In a sequential measurement of the spin components, the resolution and back-action errors of the intermediate measurement can be described by random spin flips acting on an intrinsic joint probability. If the error rates are known, the intrinsic joint probability can be reconstructed from the noisy statistics of the actual measurement outcomes. In this paper, we use the spin-flip model of measurement errors to analyze experimental data on photon polarization obtained with an interferometric setup that allows us to vary the measurement strength and hence the balance between resolution and back-action errors. We confirm that the intrinsic joint probability obtained from the experimental data is independent of measurement strength and show that the same violation of the Leggett-Garg inequality can be obtained for any combination of measurement resolution and back-action., Comment: 17 pages, 7 figures

The weak nucleon axial-vector form factor for quasielastic interactions is determined using neutrino interaction data from the K2K Scintillating Fiber detector in the neutrino beam at KEK. More than 12 000 events are analyzed, of which half are charged-current quasielastic interactions ${\ensuremath{\nu}}_{\ensuremath{\mu}}n\ensuremath{\rightarrow}{\ensuremath{\mu}}^{\ensuremath{-}}p$ occurring primarily in oxygen nuclei. We use a relativistic Fermi gas model for oxygen and assume the form factor is approximately a dipole with one parameter, the axial-vector mass ${M}_{A}$, and fit to the shape of the distribution of the square of the momentum transfer from the nucleon to the nucleus. Our best fit result for ${M}_{A}=1.20\ifmmode\pm\else\textpm\fi{}0.12\text{ }\text{ }\mathrm{GeV}$. Furthermore, this analysis includes updated vector form factors from recent electron scattering experiments and a discussion of the effects of the nucleon momentum on the shape of the fitted distributions.

A behavior of a two qubit system coupled by the electric capacitance has been studied quantum mechanically. We found that the interaction is essentially the same as the one for the dipole-dipole interaction; i.e., qubit-qubit coupling of the NMR quantum gate. Therefore a quantum gate could be constructed by the same operation sequence for the NMR device if the coupling is small enough. The result gives an information to the effort of development of the devices assuming capacitive coupling between qubits., Comment: 8 pages, 2 figures Revised and Replaced on Apr. 8 2003

Parity nonconservation (PNC) was studied in p-wave resonances in indium by measuring the helicity dependence of the neutron total cross section in the neutron energy range 6.0-316 eV with the time-of-flight method at LANSCE. A total of 36 p-wave neutron resonances were studied in {sup 115}In, and statistically significant asymmetries were observed for nine cases. An analysis treating the PNC matrix elements as random variables yields a weak matrix element of M=(0.67{sub -0.12}{sup +0.16}) meV and a weak spreading width of {gamma}{sub w}=(1.30{sub -0.43}{sup +0.76})x10{sup -7} eV. (c) 2000 The American Physical Society.