Showing papers by "TRIUMF published in 1987"
TL;DR: Transverse-field muon-spin-relaxation measurements have been performed on a superconductor and indicate a magnetic penetration depth of $\ensuremath{\lambda}\ensure Math{\approx}1400$ \AA{} which, in the limit of extreme anisotropy, reduces to $s$-wave with nodes in the gap function.
Abstract: Transverse-field muon-spin-relaxation ($\ensuremath{\mu}\mathrm{SR}$) measurements have been performed on ${\mathrm{Ba}}_{2}\mathrm{Y}{\mathrm{Cu}}_{3}{\mathrm{O}}_{9\ensuremath{-}\ensuremath{\delta}}$ ($\ensuremath{\delta}=2.1\ifmmode\pm\else\textpm\fi{}0.05$) above and below its superconducting transition temperature. The temperature dependence of the magnetic penetration depth, deduced from the $\ensuremath{\mu}\mathrm{SR}$ data, is that of an ordinary $s$-wave (not $d$-wave with nodes in the gap function) superconductor. The data at 6 K indicate a magnetic penetration depth of $\ensuremath{\lambda}\ensuremath{\approx}1400$ \AA{} which, in the limit of extreme anisotropy, reduces to $\ensuremath{\lambda}\ensuremath{\approx}1065$ \AA{}.
165 citations
TL;DR: The magnetic properties of four different phases of the YBa2Cu3Ox system, including the famous 90 K superconductor, have been probed by the positive muon spin relaxation method (µ+SR).
Abstract: The magnetic properties of four different phases of the YBa2Cu3Ox system, including the famous 90 K superconductor, have been probed by the positive muon spin relaxation method (µ+SR). The oxygen-deficient tetragonal insulating phase (x~6.2) was found to be magnetically ordered, thus most likely antiferromagnetic, near room temperature.
95 citations
TL;DR: The temperature dependence of lambda in the sintered powder sample differs from that for an ordinary homogeneous superconductor and it is shown that the longitudinal- and transverse-field ..mu..SR techniques are sensitive probes of H/sub c//sub 1/ and flux-pinning effects.
Abstract: We have performed muon-spin-relaxation (\ensuremath{\mu}SR) measurements on ${\mathrm{La}}_{1.85}$${\mathrm{Sr}}_{0.15}$${\mathrm{CuO}}_{4}$ above and below its superconducting transition temperature, ${T}_{c}$=37 K. From transverse-field \ensuremath{\mu}SR at 6 K, the magnetic penetration depth is \ensuremath{\lambda}\ensuremath{\approxeq}2500 A\r{}, which, together with previous thermodynamic data and the London formula, implies a carrier density of 0.3\ifmmode\times\else\texttimes\fi{}${10}^{22}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$. The temperature dependence of \ensuremath{\lambda} in our sintered powder sample differs from that for an ordinary homogeneous superconductor. We also show that the longitudinal- and transverse-field \ensuremath{\mu}SR techniques are sensitive probes of ${H}_{c1}$ and flux-pinning effects.
89 citations
TL;DR: In this paper, the electric dipole moment of the neutron was computed in the standard KM model, including the meson-baryon intermediate states which dominate the result in the SU (3) × SU(3) chiral limit.
60 citations
TL;DR: In this article, the magnitudes and signs of the proton and deuteron hyperfine constants are reported, and discussed in terms of isotope effects and intramolecular motion.
54 citations
TL;DR: In this paper, the authors evaluated the contribution of charge symmetry breaking (CSB) potentials to energy differences in mirror nuclei and to the scattering length differences app−ann and ann−anp from class III and class IV type CSB potentials.
48 citations
15 Jun 1987-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: The data acquisition system for the 8π spectrometer, a multidetector array for γ-ray spectroscopy, is described, based on CAMAC modules equipped with a fast auxiliary bus in ECL logic.
Abstract: The data acquisition system for the 8π spectrometer, a multidetector array for γ-ray spectroscopy, is described. It is based on CAMAC modules equipped with a fast auxiliary bus in ECL logic. The system has been designed to handle a high rate of events, each with large information content. To offer maximum flexibility for the many types of experiments envisaged, the logic of the data stream to magnetic tape has been made user selectable. This is achieved through selective hardware triggers, hardwired computations and programmed instructions in a fast microprocessor, which condense the information from each event by extracting its essential features.
41 citations
01 Jan 1987
TL;DR: In this paper, an analytic three-dimensional image-reconstruction algorithm that can utilize the cross-plane gamma rays detected by a wide solid-angle PET (positron-emission tomography) system is presented.
Abstract: An analytic three-dimensional image-reconstruction algorithm that can utilize the cross-plane gamma rays detected by a wide solid-angle PET (positron-emission tomography) system is presented. Unlike current analytic algorithms, it does not use Fourier transform methods, although mathematical equivalence to Fourier transform methods is proved. The results of implementing the algorithm are briefly discussed. An extension of the algorithm to utilize all measured cross-plane gamma rays is discussed. >
39 citations
TL;DR: In this article, the Majorana nature of neutrino in electron-electron colliders has been investigated and it was shown that a collider with s ⩾ 1 TeV and luminosity L ⩽ 10 34 cm −2 s −1 is needed to match the limits from neutrinoless double-beta decay.
31 citations
TL;DR: The relation between the four-fermion operators of the effective weak Hamiltonian in the continuum and on the lattice is calculated and various methods for performing such calculations are presented.
Abstract: We calculate the relation between the four-fermion operators of the effective weak Hamiltonian in the continuum and on the lattice. We include, at this stage, only those lattice operators which have the same dimension as the continuum operators. We consider the case where the operators contain fields which can contract with each other. We present, in a rather pedagogical fashion, various methods for performing such calculations and describe several short cuts that we have found useful.
26 citations
01 Feb 1987-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this paper, a polarimeter which uses inclusive scattering from carbon has been mounted after the focal plane of the TRIUMF medium resolution spectrometer and four drift chambers measure scatterings at all azimuthal angles out to 20° in polar angle over a spectrometers momentum acceptance of ± 5%.
Abstract: A polarimeter which uses inclusive scattering from carbon has been mounted after the focal plane of the TRIUMF medium resolution spectrometer. Four drift chambers measure scatterings at all azimuthal angles out to 20° in polar angle over a spectrometer momentum acceptance of ± 5%. A microprocessor rejects events with small scattering angles. The efficiency for 400 MeV protons is 4%, and for 295 MeV deuterons is 1.5%. Analyzing powers for protons are similar to those previously reported for polarimeters of this type.
TL;DR: In this paper, a 25 cm2 chamber with small interelectrode distances was constructed for beam profile monitoring and position tagging of rare events in spectrometers with high specific ionization.
Abstract: Gas mixtures with high specific ionization allow the use of small interelectrode distances while still maintaining full efficiency. With the short electron drift distances the timing resolution is also improved. We have built and operated two 25 cm2 chambers with small interelectrode distances. Also single wire detector cells have been built to test gas mixture lifetimes. Various admixtures of CF4, DME, Isobutane, Ethane and Argon have been tested. Possible applications of such chambers are as beam profile monitors, position tagging of rare events and front end chambers in spectrometers.
TL;DR: In this article, the three-gluon annihilation rates of 3D quarkonium states were obtained for the (1D) and (2.2, 0.26, 1.1) keV for J = (1, 2, 3).
TL;DR: A model-independent invariant cross section analysis applied to the $^{3}$,4He data at 300 MeV is used to illuminate the problems that any statistical model will face in trying to explain fragment production at intermediate energies.
Abstract: Single particle inclusive spectra have been measured for the production of several isotopes of H, He, Li, and Be from the interaction of 300 MeV protons with Be and Ag targets. $^{1}$,2H and $^{3}$,4He fragments are measured over a wide range of energies which approach the upper kinematic limits at many of the angles measured. Measurements of the isotopically resolved He, Li, and Be fragments over a more limited energy range are also reported for 190 MeV protons incident on the same two targets. The spectra have been fitted with a phenomenological moving-source model used successfully in earlier studies. However, good fits were not obtained over the extended kinematic ranges measured in this study. A model-independent invariant cross section analysis applied to the $^{3}$,4He data at 300 MeV is used to illuminate the problems that any statistical model will face in trying to explain fragment production at intermediate energies.
TL;DR: In this article, the very short 55Mn nuclear spin relaxation time (0.5μs⪷TMn1⫷30μs) was measured for the first time through zero-field μ+ spin relaxation, which reflects the nuclear spin dynamics.
TL;DR: In this article, the authors reported the angular distribution of the analyzing powers and differential cross-sections for the reaction pd → 3 He π 0 with respect to different theoretical models, none of which give fully satisfactory agreement with the cross-section data.
TL;DR: The contribution of a massivet-quark to the anomalous magnetic moment (Δκ) and the quadrupole moment of the W-boson is calculated in this paper.
Abstract: The contribution of a massivet-quark to the anomalous magnetic moment (Δκ) and the quadrupole moment (ΔQ) of theW-boson is calculated. An upper bound of Δκ=1.5×10−2 and ΔQ=2.5×10−3 for the standard model is obtained. Additional contributions from extraE6 fermions is also discussed.
TL;DR: In this paper, a charged-particle time-of-flight spectrometer capable of detecting particles with energies as low as 1 MeV was used to make these measurements, and the level density parameters of various nuclei resulting from the best simultaneous fit to present and previous 15-MeV data were inferred.
Abstract: Cross sections for the emission of protons, deuterons, and alpha particles from enriched targets of /sup 63/Cu and /sup 65/Cu bombarded with 9- and 11-Mev neutrons were measured. A charged-particle time-of-flight spectrometer capable of detecting particles with energies as low as 1 MeV was used to make these measurements. Cross sections and spectra are compared with statistical and pre-equilibrium model calculations. Level density parameters of various nuclei resulting from the best simultaneous fit to present and previous 15-MeV data are inferred.
15 Jun 1987-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this paper, a (n, p) target chamber consisting of six target layers sandwiched between seven gas detector layers was developed for simultaneous accumulation of data from multiple target materials.
Abstract: We have developed an (n, p) target chamber consisting of six target layers sandwiched between seven gas detector layers. This target chamber is now commonly used with the new (n, p) facility at TRIUMF. With this arrangement, large total (n, p) target thicknesses (> 1 g/cm 2 ) can be used and yet the target contribution to overall energy resolution is moderate, typically less than 500 keV. The simultaneous accumulation of data from six target layers has proven to be highly advantageous with a number of applications, such as; (1) using multiple thicknesses of one target material, (2) including a target of known cross-section in the target stack for normalization, (3) adding a target to obtain simultaneous spectra for later subtraction of contamination lines and (4) the use of several target materials at once.
03 May 1987-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, a facility to perform measurements of nuclear reaction rates in which one of the reactants is a radioactive species is described, and the value of these reactions to the area of nuclear astrophysics is discussed in detail and calculations of expected yields for selected examples are given.
Abstract: A facility to perform measurements of nuclear reaction rates in which one of the reactants is a radioactive species is described. The value of these reactions to the area of nuclear astrophysics is discussed in detail and calculations of expected yields for selected examples are given. This proposed facility is composed of an on-line isotope separator (ISOL) front-end coupled to a booster post-accelerator stage to raise the energy of a radioactive ion beam to sufficient energies (up to 1.5 MeV/u) to perform these studies. The advantages of this approach are presented along with a discussion of the feasibility of not only obtaining the necessary radioactive beam intensities of the important isotopes, but also of achieving the acceleration necessary. Details of one feasible accelerator system are presented.
TL;DR: In this paper, the anomalous magnetic and quadrupole moments of the W boson in SU(2)xU(1) models with two Higgs doublets were investigated.
Abstract: We present limits on the anomalous magnetic and quadrupole moments of the W boson in SU(2)xU(1) models with two Higgs doublets. We give the contributions to these moments from the charged and neutral Higgs bosons beyond the standard model. The main result is that these extra components increase the moments by 0.1% and 0.03%, respectively.
TL;DR: It is concluded that a precision analysis of the capture process must indeed includeelta effects and changes as large as 7--8X in the capture rate at the high-energy end of the photon spectrum are found.
Abstract: We examine contributions from the \ensuremath{\Delta}(1232) to radiative capture (at rest) of a muon by a nucleon This is motivated by the need for a thorough understanding of all contributing amplitudes in order to determine the pseudoscalar weak current and its coupling ${g}_{P}$ from experiments on radiative capture which are now underway or being planned We find changes as large as 7--8?in the capture rate at the high-energy end of the photon spectrum and conclude that a precision analysis of the capture process must indeed include \ensuremath{\Delta} effects
Journal Article•
TL;DR: Carbon-11-carboxyl-labeled L-dopa has been synthesized by the modified Bucherer-Strecker method and gave the product in 28% radiochemical yield (decay corrected) in an overall synthesis time of 55-60 min.
Abstract: Carbon-11-carboxyl-labeled L-dopa has been synthesized by the modified Bucherer-Strecker method. The reaction mixture was first purified by chiral HPLC followed by deprotection using hydriodic acid. The entire procedure was performed in a remotely operated system which gave the product in 28% radiochemical yield (decay corrected) in an overall synthesis time of 55-60 min.
TL;DR: In this article, the angular distributions of cross sections and analyzing powers for the radiative capture of polarized neutrons by hydrogen at E n = 370 and 478 MeV were measured and compared with a nucleon-delta coupled channels calculation.
01 Feb 1987-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this paper, the horizontal drift chambers of a relatively simple and inexpensive design were described, and the inherent left-right ambiguity in the direction of drift was resolved using the ∼ 15% difference in the signals induced on adjacent (odd or even) cathode wires.
Abstract: Horizontal drift chambers of a relatively simple and inexpensive design are described. Four of these, each with an active area of 0.89 × 0.49 m2, constitute the basic detector system for a new focal-plane polarimeter at the medium resolution spectrometer (MRS) at TRIUMF. The inherent left-right ambiguity in the direction of drift was resolved using the ∼ 15% difference in the signals induced on adjacent (odd or even) cathode wires. With separate change integration of the pulses, a normalized and corrected odd-even difference is obtained from which the horizontal drift direction is reliably deduced. The odd-even difference is found to depend sensitively on the accuracy with which the anode wire is centered in the unit cell.
TL;DR: In this paper, the properties of a photomultiplier with two sets of orthogonal anode wires were studied and the gain and position response of this device using a point light source, extended scintillators and fiber scintillation.
Abstract: We have studied the properties of a photomultiplier with two sets of orthogonal anode wires. We measured the gain and the position response of this device using a point light source, extended scintillators and fibre scintillators in several geometries. Tests were done with sources and in a pion beam. In addition we studied the high rate capabilities of the device.
03 May 1987-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: A test ISOL (TISOL) has been designed and constructed mainly for the ion-source development work necessary for the proposed TRIUMF-ISOL Facility as mentioned in this paper, which consists of two quadrupoles and a 90 ° vertical-bend dipole (QQD).
Abstract: A test ISOL (TISOL) has been designed and constructed mainly for the ion-source development work necessary for the proposed TRIUMF-ISOL Facility. The ion-beam transport and isotope separator system consists of two quadrupoles and a 90 ° vertical-bend dipole (QQD). One special feature of TISOL is that the relative position of the quadrupole doublet may be adjusted so as to accommodate a large variety of target-ion-sources (TIS). These will include surface ionization, plasma, on-line Electron Cyclotron Resonance (ECR) and laser-based ion sources. The performance of the QQD for various TIS systems will be discussed. The calculated resolution (based on second-order TRANSPORT) for an emittance of 25 π mmmrad in the bend plane and 120 π mmmrad in the non-bend plane is about one in 1000. The facility is presently under development and the optimal optical configuration has not yet been achieved.
TL;DR: Using the lifetime technique, atomic capture ratios of negative muons have been measured in 41 oxides as discussed by the authors, and the results were consistent with the mesic X-ray measurements.
TL;DR: In this paper, a newly constructed focal plane polarimeter for the medium resolution spectrometer at TRIUMF was used to measure polarizations and polarization transfer coefficients for protons elastically scattered from 208Pb at 290 MeV.
TL;DR: In this paper, the first measurements of the tensor analyzing power in the elastic scattering reaction were made using a tensor polarized deuteron target, and the results were shown to be in agreement with Faddeev calculations.
Abstract: The first measurements of the tensor analyzing power ${T}_{21}$ in the \ensuremath{\pi}d elastic scattering reaction have been made using a tensor polarized deuteron target. Eleven angles were studied at a pion bombarding energy of 180 MeV. The results are shown to be in agreement with Faddeev calculations.