Kaon production in\bar pp interactions at c.m. energies from 200 to 900 GeV

A detailed analysis ofK _s ⁰ production in \(\bar pp\) |<2.5 the average transverse momentum is found to be 0.53±0.07 GeV/c at 200 GeV and 0.62±0.08 GeV/c at 900 GeV, which is an increase with respect to data at c.m. energies below 60 GeV. TheK _s ⁰ production cross sections in inelastic collisions are 29±4 mb at 200 GeV and 63±6 mb at 900 GeV, showing an increase compared to lower energy data. The central kaon density is found to increase as a logarithmic function of energy. At 900 GeV, where statistics are sufficient to allow one to draw conclusions, the average transverse momentum is higher in events with large charged multiplicity than in events with low multiplicity.     

Phase space dependence of the multiplicity distribution in π+ andpp collisions at 250 GeV/c

The charged particle multiplicity distribution has been studied for non-single-diffractive π⁺ p andpp collisions at \(\sqrt s = 22\) GeV, for full phase space as well as for intervals in rapidity, azimuthal angle and transverse momentum. In general, the multiplicity distribution is well described by a negative binomial. From comparison of the distribution for negative or positive particles to that of all charged particles, cascading is favoured as an interpretation over stimulated emission. Interesting consequences follow from a comparison of our results to those at collider energies and toe ⁺ e ^? data at comparable energy. Furthermore, evidence is given that the multiplicity distribution is not exactly of negative binomial type in every (connected or disconnected) phase space region.     

Forward-backward multiplicity correlations in σ+ p,K + p andpp collisions at 250 GeV/c

Forward-backward multiplicity correlations in σ⁺,K ⁺ p andpp collisions at 250 GeV/c ( \(\sqrt s \) =22 GeV) are given for all charges and for the different charge combinations. The correlations are found to be caused predominantly by centrally produced particles. It is demonstrated that this result is an agreement with observations at the ISR and the CERNp \(\bar p\) -Collider. The results are compared to expectations from LUND, DPM and FRITIOF Monte Carlo models and a geometrical picture relating correlations in hadron-hadron collisions toe ⁺ e ^? data in terms of impact parameters is tested.     

Frequency stability of an optically pumped cesium beam frequency standard

Results obtained in an experimental optically pumped cesium beam frequency standard in which a single semiconductor laser is used for the state selection and the atom detection are reported. The separation between the two interaction regions is equal to 21 cm. This gives a 500 Hz linewidth which is observed with a signal to noise ratio equal to 10,000 in a 1 Hz noise bandwidth. A quartz crystal oscillator is frequency controlled by the atomic transition. The measured short term frequency stability is given by _y()=2×10^–12–1/2 for 1 s<500 s. Prospects for improvement of this frequency stability are discussed.     

Spectroscopic investigation of the ionization kinetics in XeCl laser discharges by Xe* density measurements

Time and spatially resolved absorption measurements of Xe^* particle number densities performed at an X-ray preionized self-sustained XeCl^*-laser discharge were used to investigate the reaction kinetics of such discharges and to test the validity of the commonly-made assumption that they are fit well by spatially homogeneous numerical models. It turned out that the Xe^* density distribution over the discharge cross section remains homogeneous for less than 100 ns only. Comparing the experimental results of the homogeneous discharge phase with zero-dimensional model calculations, we conclude that induced emission modeled using two excited xenon levels must be taken into account for the quantitative interpretation of the absorption measurements. For the interpretation of the Xe 6s-6p absorption measurements even a multilevel model will be necessary. Further we conclude from the relative courses and the absolute values of the Xe^* particle number densities that realistic HCl kinetics should contain three vibrationally excited levels and stepwise excitation processes as proposed by Dem'yanov et al. [8].     

Tunable UV laser photolysis of organometallics with product detection by laser mass spectroscopy: Trimethylaluminum

We use tunable UV laser light in the region 200–320 nm, produced by frequency doubling the output of a dye laser, for the decomposition of organometallic compounds. This method has been applied to TMA, trimethylaluminum Al(CH₃)₃. Only the TMA monomer absorbs UV light for >220 nm. TMA decomposes by one-photon absorption mainly into two channels: aluminum atoms Al plus organic fragments, and aluminummonomethyl AlCH₃ molecules plus organic fragments. The ratio [Al]/[AlCH₃] is wavelength dependent. We present a mechanism to explain the photolysis of trimethyl compounds of group III elements (Al, Ga, In).     

Synthesen von Heterocyclen, 122. Mitt.: Über die Reaktion des Perimidons mit aktiven Malonestern

Zusammenfassung Perimidon (1) reagiert mit monosubstit. Malonsäure-trichlorphenylestern (2) bei 250° zu 9-Hydroxy-5,7-dioxo-4,5-dihydro-7H-pyrido[1,2,3-cd]perimidinen (3), die durch saure Hydrolyse zu 10-Amino-4-hydroxy-benzo[h]carbostyrilen (4) gespalten werden.

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Syntheses of heterocycles, CXXII: Reaction of perimidone with reactive malonates

Perimidone (1) reacts with monosubstituted 2.4.6-trichlorophenyl malonates at 250° to 9-hydroxy-5.7-dioxo-4.5-dihydro-7H-pyrido[1.2.3-cd]perimidines (3), which are cleaved by acid yielding 10-amino-4-hydroxy-benzo[h]quinolin-2-ones (4).

     

Positron annihilation studies in highT c superconductor YBa2Cu3Cd x O y (x=0, 0.05)

Positron lifetime and Doppler broadening of the annihilation line measurements were performed in highT _c superconducting samples YBa₂Cu₃Cd _x O _y ,x=0, 0.05 and 6.9<y<7, as a function of temperature in the region of 14–300 K. It was found that the positron lifetime and theS parameter values are lower in the Cd doped sample than those in the undoped one. It was also observed that the positron annihilation parameters show similar temperature dependence for the undoped and Cd doped samples. We conclude that the Cd doping in highT _c superconductor YBa₂Cu₃Cd _x O _y , 6.9<y<7 fills defects associated with oxygen vacancies probably in oxygen deficient regions which can trap positrons.