Neutral-pion photoproduction off protons in the energy range 0.3 GeV<E(gamma)<3 GeV

Single pi(0) photoproduction has been studied with the CB-ELSA experiment at Bonn using tagged photon energies between 0.3 and 3.0 GeV. The experimental setup covers a very large solid angle of approximately 98% of 4pi. Differential cross sections dsigma/dOmega have been measured. Complicated structures in the angular distributions indicate a variety of different resonances being produced in the s channel intermediate state gammap-->N(*)(Delta(*))-->ppi(0). A combined analysis including the data presented in this letter along with other data sets reveals contributions from known resonances and evidence for a new resonance N(2070)D15.     

Spectra of direct excitation of phosphorescence in an isotopic mixed naphthalene crystal. High resolution excitation of the two Davydov components of the N-d8 host crystal

Direct excitation spectra of the triplet exciton band of deuterated naphthalene are presented. The high resolution spectra (0.1 cm^?1) of the two Davydov components show a substructure that we attribute to the presence in the crystal of natural traps and local strains. A model based on the calculation of the eigenstates of a finite plane of molecules is provided for lineshape simulations. In this work the artificial edge effects introduced by the finite size of the model crystal are eliminated by appropriate boundary conditions. Our method allows us to introduce a random distribution of traps, with variable energies, located inside and outside the exciton band, thus featuring a real crystal. Comparison between calculations and experimental results accounts for the salient effects of the traps on the spectroscopic properties of a mixed crystal.     

A general transformation for theta series associated with the quadratic form $$x^2+ky^2$$

Using elementary techniques, we prove a general transformation for theta series associated with the quadratic form \(x^2+ky^2.\) The transformation is then applied to establish several infinite families of identities involving theta series whose Fourier coefficients are interlinked.     

On certain pairs of <Emphasis Type="Italic">q</Emphasis>-series identities

Hirschhorn recently proved a pair of q-series identities that interlinked the coefficients of two infinite products. We use the theory of modular forms to extend his results from \(p=5\) to other primes and provide other examples of infinite products sharing similar properties.     

Spectra of direct excitation of phosphorescence in an isotopic mixed naphthalene crystal

Distributed polarizabilities of a series of n-alkanes C _n H_2n+2 (n = 2-7) in various conformations have been determined using Bader's topological theory of atoms in molecules. Using an appropriate localization scheme, a simple distributed model is constructed, where the methyl and methylene groups are characterized by their dipole polarizability tensors in local frames, and all charge flow polarizabilities between them are retained. A set of average polarizability parameters is proposed that takes into account the local environment of the methyl and methylene groups, and that not only reproduces the polarizability tensor for any member of the n-alkane series in an arbitrary conformation, but also is suitable for the calculation of induction energies.     

Modification of the omega-meson lifetime in nuclear matter

Information on hadron properties in the nuclear medium has been derived from the photoproduction of omega mesons on the nuclei C, Ca, Nb, and Pb using the Crystal Barrel/TAPS detector at the ELSA tagged photon facility in Bonn. The dependence of the omega-meson cross section on the nuclear mass number has been compared with three different types of models: a Glauber analysis, a Boltzmann-Uehling-Uhlenbeck analysis of the Giessen theory group, and a calculation by the Valencia theory group. In all three cases, the inelastic omega width is found to be 130-150 MeV/c(2) at normal nuclear matter density for an average 3-momentum of 1.1 GeV/c. In the rest frame of the omega meson, this inelastic omega width corresponds to a reduction of the omega lifetime by a factor approximately 30. For the first time, the momentum dependent omegaN cross section has been extracted from the experiment and is in the range of 70 mb.     

A variation of the Andrews–Stanley partition function and two interesting q-series identities

The Ramanujan Journal - In this paper we present a new formula for the number of unrestricted partitions of n. We do this by introducing a correspondence between the number of unrestrited...     

Synthesis of an aluminum nitride–yttria (AlN–Y2O3) composite from nano-sized porous AlN and YCl3

In order to enhance the thermal conductivity of aluminum nitride (AlN) with sintering additives including yttria (Y₂O₃), it is necessary to form yttrium aluminate garnet (YAG) and secondary phases both within and around the boundaries of AIN drains. Nano-sized porous AlN particles were produced to form YAG and secondary phases within AlN grains, after which a AlN–Y₂O₃ nano–nano composite was formed from AlN and amorphous Y₂O₃. Porous AlN powders were first successfully synthesized by the chemical vapor synthesis (CVS) method. Highly crystalline and nano-sized porous AlN powders were synthesized at 1,200 °C. Brunauer–Emmett–Teller (BET) analysis showed that these powders had very large surface areas, suggesting that the particles approached nano-scale sizes with very small pores. To form composites of Y₂O₃ and AlN, we prepared a yttrium source solution that infiltrated the nano-sized pores of the AlN particles. Such an infiltration of AlN with amorphous Y₂O₃ was expected to effectively reduce the residual oxygen content by facilitating the formation of YAG and secondary phases during the sintering process. We characterized the composite powders of AlN–Y₂O₃ and the sintered bodies using BET, XRD, SEM, TEM, and thermal conductivity analyses.

     

Low-energy photoproduction of \omega-mesons

The photoproduction of the vector meson has been studied between threshold and W = 2.4 GeV with the SAPHIR detector at the Bonn electron stretcher ring ELSA. Besides, the total cross-sections angular distributions in the CMS and decay angular distributions in the helicity and Gottfried-Jackson systems have been measured.Received: 26 February 2003, Revised: 20 May 2003, Published online: 9 October 2003PACS: 14.40.Cs Properties of specific particles: Other mesons with S = C = 0, mass < 2.5 GeVJ. Barth: Part of doctoral thesis [1].W. Braun: No longer working at this experiment.