Vector two-point functions in maximally symmetric spaces

We obtain massive and massless vector two-point functions in maximally symmetric spaces (and vacua) of any number of dimensions. These include de Sitter space and anti-de Sitter space, and their Euclidean analogsS ⁿ andH ⁿ. Our method is based on a simple way of constructing every possible maximally symmetric bitensorT _a...bc...d(x, x) which carries tangent-space indicesa...b atx andc...d atx.     

The decay of spin-isospin modes in a semi-infinite slab

The surface response for charge exchange (p, n) and (³He, T) reactions is studied in the-region using the semi-infinite slab model. The contribution to the total response from different decay channels, (NN, N, ), is calculated. These decay channels corresponds to the exclusive channels, (pp, p ⁺, ⁺), measured in recent (p, n) and (³He, T) experiments. The in-medium properties of the-resonance is taken into account by using microscopic calculations of the-width in nuclear matter. From the-width in nuclear matter a non-local imaginary-potential, as well as a local potential, is constructed for the semi-infinite slab model. The results in the semi-infinite slab model gives a qualitative understanding of the exclusive experiments. The exclusive (NN, N, ) channels are more sensitive, than the total response, tog-correlation parameters,-width and the absorption function used at the external vertex. Our calculations suggest low values of theg-correlation parametersg _N andg , (0.3). The results with the-width represented as a non-local or a local-potential are very similar, with only minor differences in the exclusive channels.Supported in part by the Swedish Natural Science Research Council and by the Director, Office of Energy Research, Office of High Energy and Nuclear Physics, Nuclear Physics Division of the U.S. Department of Energy under Contract No. DE-ACO3-76SF00098     

Studies of the reactionπ − p→η ′ π 0 n at 38 and 100 GeV/c

The production of ⁰ system in ^– _p charge-exchange interactions at ^– momenta 38 GeV/c and 100 GeV/c has been studied. The 2 and ^{0 0} decay modes of leading to 4 and 8 final states respectively have been detected. No statistically significant peak is observed in the ⁰ mass spectrum in the range of 1.2 GeV÷2.1 GeV. An upper limit of 6·10^–3 has been established for thea ₂ ⁰ (1320) ⁰ branching ratio.     

An upgraded analysis of ɛ′/ɛ at the next-to-leading order

An upgraded analysis of ,x _d and /, using the latest determinations of the relevant experimental and theoretical parameters, is presented. Using the recent determination of the top quark mass,m _t =(174±17) GeV, our best estimate is /=(3.1±2.5)×10^–, which lies in the range given by E731. We describe our detemination of / and make a comparison with other similar studies. A detailed discussion of the matching of the full theory to the effective Hamiltonian, written in terms of lattice operators, is also given.     

Correlation tensors of the blackbody radiation in rectangular cavities

Electromagnetic equilibrium fluctuations in finite cavities filled with a dissipative medium (dielectric function ()=+i) and bounded by walls of infinite conductivity are considered. Expanding the fields in terms of a complete and orthonormal set of functions and solving the Maxwell equations the response of the EM field to external forces (polarization and magnetization) is obtained. With the aid of the fluctuation dissipation theorem and the linear response functions the 2nd order correlation tensors of the EM field are derived.For rectangular cavities explicit considerations are made. In the case of transparent media (=0) the spectral energy density of the EM radiation is calculated.     

The decays of theρ′1 andω′1 mesons

New measurements of the reactione ⁺ e ^– confirm previous evidence for the decay₁ and provide a strong constraint on the mass of the₁. The results from a detailed analysis of these data are compared with those from a corresponding analysis of new data on the reactione ⁺ e ^–. It is shown that in accord with expectation. This identification of a strong₁ decay supports a previous claim that the₁ and theC(1480), observed in the channel, cannot be different manifestations of the same particle.     

Spectroscopic properties of the photoproducts of pyridoxal-5′-P irradiation: Catalytic site recognition of ribonuclease A

Photoproducts of pyridoxal-5-P, i.e., 4-pyridoxic-5-P and bis-pyridoxal-5-P, have been studied by spectroscopic methods. The spectroscopic properties of bis-pyridoxal-5-P (bis-PLP) resemble those of pyridoxal-5-P (PLP) under similar experimental conditions. The coupling of methylen hydrogens to the phosphorus atom has been shown by NMR spectroscopy. The singlet in the³¹P-NMR spectra and the triplet in¹H-undecoupled experiments confirm the presence of the phosphate group in the 5 position of the structure of the vitamin. The effect of pH and solvent composition on the relative distribution of species of bis-pyridoxine-5-P (bis-PNP) has been investigated by absorption and fluorescence spectroscopy. The acid-base dissociation of the phosphate group is easily detected by emission spectroscopy. Bis-PNP and bis-PLP bind to the enzyme RNase A and they behave as competitive inhibitors with respect to the substrate cytidine-2-3-cyclic phosphate. The natural forms of vitamin B₆, pyridoxine, and pyridoxine-5-P have no effect on the catalytic activity of the protein. Experimental evidence derived from fluorescence and inhibition experiments is consistent with the hypothesis that bis-PNP recognizes the catalytic site of RNase A.     

Masses of colored vector mesons

Mass formulas for colored vector mesons are derived under the assumption of one common mixing angle forSU(3), independent of the color quantum numbers, and correspondingly one common mixing angle () forSU(3). This a priori plausible assumption turns out to have strong implications and thus might be too restrictive. We allow for a non-trivial spatial overlap integral between color-singlet and color-octet states. Various cases are treated and physical possibilities are identified. The best agreement is obtained for = 0. There are two models of this type with and without a part of the symmetry breaking Hamiltonian density transforming as (Y, Y) underSU(3)SU(3). Models with 0 are also possible. They cannot have a (Y, Y) and predict 3.34 GeV as the mass of the (3.7). This error of 10% may however be used to reject this possibility. Masses of colored vector mesons are predicted in the various models. If a (Y, Y) is present, ideal mixing inSU (3) is implied by the general formalism of the model.     

Analytical Electron Microscopy Examination of the γ′/γ Interfaces in a Ni-Based Superalloy

The investigation of microstructure and chemical composition of the and phases were performed in a Ni-base superalloy by means of analytical electron microscopy. The distribution of particular elements in the alloy was revealed using X-ray mapping in a transmission electron microscope. The detected concentration profiles of alloying elements at the / interface were relatively sharp in the case of cuboidal shape of the phase while they resembled the classical diffusion profile for the oval phase. The quantitative analysis of the phase revealed much higher content of Al and lower of Ti, W, Co and Mo in the oval precipitates compared to cuboidal ones. This result is attributed to the different solidification paths, which is eutectic for the cuboidal precipitates and peritectic for the oval precipitates.     

S0-S1 two photon absorption dynamics of organic dye solutions

The two-photon absorption cross-sections and excited-state absorption cross-sections of the dyes rhodamine 6G, methylene blue and fuchsin dissolved in methanol, and of the dyes safranine T, 1,3,3,1,3,3-hexamethylindocarbocyanine iodide (HMICI) and 1,3,1,3-tetramethyl-2,2-dioxopyrimidi-6,6-carbocyanine hydrogen sulphate (PYC) dissolved in hexafluoroisopropanol (HFIP) are determined. The excitation is achieved with picosecond light pulses of a passively mode-locked Nd-glass laser (_L = 1.054m). The influence of amplified spontaneous emission on the two-photon absorption dynamics is analysed.     

On the possibilities to study the exotic state 1−+ in photoproduction of the πη, πη′ systems

We show that photoproduction experiments provide propitious conditions to study the exotic state 1^–+ in the and channels. For unpolarized photons contributions from natural and unnatural parity exchanges do not interfere with each other, a fact which permits to estimate the correctness of phase shift analyses. In photoproduction of the ⁺ system in the mass range ofa ₂(1320) a more stringent limit on the product (1^–+)Br(1^–+) can be obtained than in experiments on Primakoff production on nuclei. Particularly favourable is the study of the state 1^–+ in the coherent photoproduction of the ⁰ and ⁰ systems on nuclei, with significantly enlarged statistics and a simplified phase shift analysis.     

The sphaleron at non-zero Weinberg angle

The sphaleron solution is calculated as a perturbation expansion in (g/g), to . For the physical value (g/g)=0.55 the original spherically symmetric sphaleron is a good approximation. However we expect the expansion to break down at (g/g)2 and the true solution to deviate strongly from the original solution above this value.     

Navier and stokes meet the wavelet

We work in the space = of divergence-free measurable vector fields onR ³ complete in the norm , where     

Excitations in208Pb nearE x=5683 keV

A search for the recently proposed two-phonon octupole vibrational (2-POV) 4⁺ or 6⁺ state in²⁰⁸Pb at an excitation energy of 5683 keV has been performed using the²⁰⁷Pb(d,p),²⁰⁸Pb (p,p) and (,) reactions at high energy resolution. No evidence for a two-phonon excitation at this energy is found.This work was supported in part by the DFG under contract nr. II C4-Gr 894/2-1 and by the DFG-Graduiertenkolleg Struktur der Hadronen und Kerne under contract nr. Mu 705/3-1.     

Experimental study of hard photon radiation processes at HERA

We present an experimental study of theepe+p andepe+X processes using data recorded by the H1 detector in 1993 at the electron-proton collider HERA. These processes are employed to measure the luminosity with an accuracy of 4.5 %. A subsample of theepe+X events in which the hard photon is detected at angles 0.45 mrad with respect to the incident electron direction is used to verify experimentally the size of radiative corrections to theepeX inclusive cross section and to investigate the structure of the proton in theQ ² domain down to 2 GeV², lower than previously attained at HERA.Supported by the Bundesministerium für Forschung und Technologie, FRG under contract numbers 6AC17P, 6AC47P, 6DO57I, 6HH17P, 6HH27I, 6HD17I, 6HD27I, 6KI17P, 6MP17I, and 6WT87P     

Observation of the decaya 2 − (1320)→π − η′

The reaction ^– C ^– C has been studied at 36 GeV/c. A clear signal for the decaya ₂ ^– (1320) ^– · is observed in the ^– mass spectrum. The measured ratio of branchings is BR (a ₂ ^{– –} )/BR(a ₂ ^{– –} );(3.4±0.8±0.5)·10^–2.     

Excition dynamics in the J-aggregates of a carbocyanine dye

We report on the exciton dynamics in the J-aggregating dye 5,5, 6,6-tetrachloro-1,1-diethyl-3,3-di(4-sulfobutyl)-benzimidazolocarbocyanine which is known readily to form J-aggregates, even at room temperature and at a low concentration. We performed a series of time-correlated singlephoton-counting experiments at different emission wavelengths and at different temperatures in the range between 1.5 and 125 K. Additionally, the temperature dependence of the relative fluorescence quantum yield was determined.     

Continued fractions and fermionic representations for characters of M(p,p′) minimal models

We present fermionic sum representations of the characters _{, s} ^{(p, p)} of the minimal M(p,p) models for all relatively prime integers p>p for some allowed values of r and s. Our starting point is biomial (q-binomial) identities derived from a truncation of the state counting equations of the XXZ spin 1/2 chain of anisotropy –=–cos((p/p)). We use the Takahashi-Suzuki method to express the allowed values of r (and s) in terms of the continued fraction decomposition of {p/p} (and p/p), where {x} stands for the fractional part of x. These values are, in fact, the dimensions of the Hermitian irreducible representations of SU _q- (2) (and SU _q+ (2)) with q–=exp(i{p/p}) (and q+=exp(i(p/p))). We also establish the duality relation M(p,p) M(p–p,p) and discuss the action of the Andrews-Bailey transformation in the space of minimal models. Many new identities of the Rogers-Ramanujan type are presented.Dedicated to Prof. Vladimir Rittenberg on his 60th birthday     

The analytic structure of the anomalous dimension of the four-gluon operator in deep inelastic scattering

The phenomenology of the pseudoscalar (1440) meson (also known as l) is discussed in a simplified , l mixing scheme in which the is assumed to have no glueball component. The parameters of the model are quite well constrained from the and two-photon decays. First it is shown that the scheme is in rather good general agreement with (almost) all the available data. Then a number of testable predictions concerning decays involving the iota are made. The iota turns out to be largely a glueball in this model.