The half-life of87Rb measured as difference between the isotopes87Rb and85Rb

The half-lifeT of⁸⁷Rb was determined by means of a 4π proportional counter using thin sources of RbCl on thin conducting backings. The total thicknessD investigated (RbCl+support) ranged from 11 to 525 μg/cm². Comparative measurements with (inactive) layers of⁸⁵RbCl showed that, in the energy range below 185 eV, RbCl layers give rise to spurious pulses. Linear extrapolation of the specific activity belowD=45 μg/cm² toD=0 yieldsT=(4.88 _?0.10 ^+0.06 )·10¹⁰ y. Previously published half-lives are discussed.     

Surface electron scattering in d-wave superconductors

A theoretical model of a rough surface in a d-wave superconductor is studied for the general case of arbitrary strength of electron scattering by an impurity layer covering the surface. Boundary conditions for quasiclassical Eilenberger equations are derived at the interface between the impurity layer and the d-wave superconductor. The model is applied to the self-consistent calculation of the surface density of states and the critical current in d-wave Josephson junctions. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 3, 242–246 (10 February 1999) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Progress of the 87Rb Fountain Clock

A fountain atomic clock based on cold 87Rb atoms has been in operation in our laboratory for several months. We therefore report the design of the rubidium fountain clock including its physical package, optical system and daily operation. Ramsey fringes have been attained with the signal to noise ratio of about 100.     

Poles and zeros in ππ scattering amplitudes

We draw attention to the remarkable systematics exhibited in the ππ amplitudes provided by the CERN-Munich data. It is shown that the existence of resonance poles with specific spin and mass values and the behaviours of the amplitude zeros in the Mandelstam plane give strong support to the ideas associated with dual resonance models. It is emphasized that some gauge-like conditions of dual resonance models play an essential role in these considerations.     

Pulse loading ~(87)Rb Bose-Einstein condensation in optical lattice:the Kapitza-Dirac scattering and temporal matter-wave-dispersion Talbot effect

<正>We study ~(87)Rb Bose-Einstein condensation(BEC) loading into the pulse of the one-dimensional(1D) optical lattice experimentally.The lattice is turned on abruptly,held constant for a variable time,and then turned off abruptly.The measurement of the depth of the optical lattice is obtained by Kapitza-Dirac scattering.The temporal matter-wave-dispersion Talbot effect with ~(87)Rb BEC is observed by applying a pair of pulsed standing waves(as pulsed phase gratings) with the separation of a variable delay.     

Incommensurate CDW in Rb0.3MoO3: 87Rb NMR

The ⁸⁷Rb NMR measurement was carried out in a single-crystal Rb_0.3MoO₃. Below 180 K the NMR line well characterized the existence of incommensurate CDW. The absence of lock-in transition was confirmed from the temperature dependence of line shape. The CDW held the incommensurate phase even at 77 K, in spite of the nearly commensurate value of CDW wave vector observed in the neutron diffraction experiment. The CDW amplitude obtained from NMR was consistent with the BCS curve.     

Unitarity structure of scattering amplitudes

As a first step towards constructing scattering amplitudes satisfying unitarity, analyticity and crossing symmetry, we derive a linear non-singular integral equation for the total scattering amplitude which is equivalent to the unitarity condition. For this purpose we use the partial-waveN/D representation (with inelasticity) and the convolution theorem for Legendre transforms. We also discuss briefly the choice of two functionsN(s, cos Θ),C(s, cos Θ) which determine the unitary scattering amplitude through the integral equation. These functions may hopefully be chosen so that the analyticity and crossing symmetry requirements are satisfied.

     

Rb87 spin-lattice relaxation in RbMnF3

Nuclear spin-lattice relaxation rate measurements of Rb⁸⁷ in the isotropic antiferromagnet RbMnF₃ have been performed from 27 to 500°K. Both the high temperature value of the relaxation rate and its temperature dependence are well explained by a theoretical calculation essentially based on Moriya's theory.     

Recursion relations and scattering amplitudes in the light-front formalism

The fragmentation functions and scattering amplitudes are investigated in the framework of light-front perturbation theory. It is demonstrated that, the factorization property of the fragmentation functions implies the recursion relations for the off-shell scattering amplitudes which are light-front analogs of the Berends–Giele relations. These recursion relations on the light-front can be solved exactly by induction and it is shown that the expressions for the off-shell light-front amplitudes are represented as a linear combinations of the on-shell amplitudes. By putting external particles on-shell we recover the scattering amplitudes previously derived in the literature.     

New determination of the neutron-proton scattering amplitude and precise measurements of the scattering amplitudes on carbon,chlorine, fluorine and bromine

After an improvement on the theory of the neutron-gravity-refractometer and after refinements of the experimental procedure we have performed new measurements of the absolute value of the neutron-proton scattering amplitude at low neutron energies. In order to obtain and to confirm a very high accuracy we carried out neutron-reflection experiments on 18 various liquids of 11 different organic substances containing the elements carbon, hydrogen and/or chlorine. Compounds with fluorine and bromine were used to measure the scattering amplitudes of these elements. We found the coherent scattering amplitudes of the bound atoms to be:a _H=?3.7409(1l)fm,a _c=6.6484(13)fm,a _c1=9.5792(8)fm,a _F=5.66(2)fm anda _Br=6.79(2)fm. The low energy (n, p)-parametersa _t anda _s were calculated with the presenta _H and a new value of the (n, p) scattering cross-sectionσ ₀. By comparing the measureda _C with values obtained from precise transmission experiments we could determine the gravitational accelerationg _f of the free neutron in terms of the local value g. We found the two values to be equal:g _f =0.9996(7)g.     

Regge poles in multiparticle scattering amplitudes

A study is made of the high-energy limits of multi-particle scattering amplitudes in a φ³ theory. A limited set of chekerboard diagrams dominate the asymptotic behavior .The diagrams sum to produce Regge poles. If N is the number of particles bound together, the trajectory functions of the leading Regge poles are given by α(N)=? (2N ? 3) +g²8π²m². Comparison is made with the generalized multiperipheral model of Auerbach, Aviv, Sugar and Blankenbecler in which the corresponding trajectories have the form α(N)=a?bN+cN².     

Quark-hadron duality and meson-meson scattering amplitudes

We investigate a special concept of quarkhadron duality in meson physics at low and intermediate energies. With a relativistic propagator for confined quarks, we calculated masses and widths of the mesons which areS- andP-wave states ofq¯q (J ^P=0^?, 1^?, 0⁺, 1^+c, 2⁺) as well as meson-meson scattering amplitudes at energies up totrs ≤ 1.3 GeV by including light pseudoscalar and vector mesons into the interaction dynamics. Our investigation shows that the influence of the light meson dynamics resutls in:

1. a contribution to the constituent quark mass of approximately 200 MeV.
2. the appearance of a new soft confinement force barrier responsible for the formation of the highly excited meson states.

     

Double-cut of scattering amplitudes and Stokes' Theorem

We show how Stokes' Theorem, in the fashion of the Generalised Cauchy Formula, can be applied for computing double-cut integrals of one-loop amplitudes analytically. It implies the evaluation of phase-space integrals of rational functions in two complex-conjugated variables, which are simply computed by an indefinite integration in a single variable, followed by Cauchy's Residue integration in the conjugated one. The method is suitable for the cut-construction of the coefficients of 2-point functions entering the decomposition of one-loop amplitudes in terms of scalar master integrals.     

The low-lying level structure of87Rb

The low-lying states of⁸⁷Rb are studied in the framework of a quasiparticle-core coupling model. The agreement between the calculated and experimental level spectra, stripping strength, ground state static electromagnetic moments and theE2 transition rate of the first excited state is good. Electromagnetic moments and transition rates for other excited states are predicted.     

Dual pairs and representations of scattering amplitudes

A procedure for constructing scattering amplitudes for production processes that is exactly unitary, preserves the bosonic character of the many-particle states, and is invariant with respect to an underlying symmetry group is given. Two simple models, dealing with isospin internal symmetry and the two-dimensional Euclidean space group are presented which illustrate how scattering amplitudes can be represented as matrix elements of groups whose action commutes with the action of the invariance group on the relevant Fock space.Invited talk presented at the International Conference Selected Topics in Quantum Field Theory and Mathematical Physics, Bechyn, Czechoslovakia, June 23–27, 1986.Work supported in part by the Department of Energy.     

Geometrical scaling and analyticity of scattering amplitudes

Geometrical scaling connects, att=0, the phase of the Pomeron amplitudeF(s, t) to that of its derivativeF(s, t)/t. This intrinsic phase correlation allows one to derive a dispersive sum rule which strongly relates the high- and low-energy regions.Presented at the Symposium on Hadron-Hadron Scattering at High Energies, Liblice, Czechoslovakia, June 16–21, 1975.Thanks are due to D.Robertson and J.Dias de Deus for useful discussions.     

On the low-energy πN scattering amplitudes

The pion-nucleon scattering amplitudes with current algebra constraints involving “remainder terms” are calculated by saturating them with the N¹(1236) contribution having off-mass shell effects and compared with experiments.