Mass and lifetime limits on new long-lived particles in 300 GeV/c π− interactions

A sensitive search has been done for the production of new long-lived and penetrating particles by 300 GeV/c negative pions. No new state —decaying into at least two charged known particles —has been detected with mass above 1 GeV/c² and lifetime in the range 5·10^?11 s to 5·10^?7s. We give upper limits on production cross sections, and consequences on the existence of heavy “axion-like” particles, heavy neutrinos and supersymmetric particles. In particular, this experiment excludes the existence of light gluinos with lifetime in the range 5·10^?11 to 10^?8s: this closes the last “window of opportunity” for gluinos withM<2 GeV/c² and lifetime measurable in particle physics experiments.     

A novel bicyclic phosphonium ylide from the reaction of a 1,2-dihydrophosphorin with dimethyl acetylenedicarboxylate.

The reaction of 1,2,5-triphenylphospholium fluorenylide with dimethyl acetylenedicarboxylate gives two 1:1 adducts, one of which is shown by X-ray analysis to have a novel 1-phosphabicyclo[3.2.1]octatriene structure.     

Inclusive π0 and η production in the all neutral mode from 100 GeV/cπ−p collisions

Results are givenfor π⁰ and η production in 100 GeV/cπ^?p collisions, summed over all final states with no charged particles present (the all neutral final states). The data are fitted for x?0.6 to a modification of triple Regge theory suggested by the multiperipheral model. We find good agreement between the values of the ? and A₂ trajectories determined in the all neutral process, the full inclusive mode, π^?p → (π⁰, η)X, and the exclusive reactions, π^?p → (π⁰, η)n. The ? exchange residue function shows evidence for a dip at t ≈ ?0.5 (GeV/c)² (the ? wrong signature nonsense zero), whereas the η data are quite smooth in this region. These successful predictions for both the trajectory and residue function are striking evidence for the validity of triple Regge theory.     

Periodic fluid transients in cylindrical ducts with transverse magnetic fields

Summary This paper treats periodic fluid transients in liquid metals contained in constant-area circular ducts with uniform, transverse, applied magnetic fields. The magnetic Reynolds and Mach numbers are assumed to be small, and the Reynolds number is assumed to be large. By the use of a complex coordinate transformation, closed-form solutions are obtained for the perfectly conducting duct. By the same technique, solutions in series of Mathieu functions are obtained for the fully insultating duct. A method for solving the dispersion relation for each case is outlined, and sample numerical results are presented.

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Résumé Cet article traite des ondes de compression périodiques dans un métal liquide contenu dans une conduite circulaire avec une section droite qui est constante et avec un champ magnétique transversal et uniforme que l'on applique. Ici on suppose que le nombre magnétique de Reynolds et le nombre de Mach sont petits et que le nombre de Reynolds est grand. A l'aide d'une transformation complexe des corrdonnées on obtient des solutions éxactes pour une conduite qui est parfaitement conductrice. Par le même technique on trouve les solutions pour la conduite parfaitement isolante dans une série de fonctions de Mathieu. Une méthode pour la solution de l'équation de dispersion est esquissée et des exemples de résultats numériques sont présentés.

     

Iodine magnetic moments measured by on-line nuclear orientation

On-Line measurements of magnetic dipole moments of^117–122I are interpreted using coupling of the odd particles to a deformed core. The results show interesting effects of g_7/2, d_5/2 orbital admixtures in the odd-A isotopes, which are close to spherical. The odd-odd isotopes^{118, 120}I show clear examples of shape co-existence.     

A branch and bound algorithm for solving the multiple-choice knapsack problem

The multiple-choice knapsack problem is a binary knapsack problem with the addition of disjoint multiple-choice constraints. We describe a branch and bound algorithm based on embedding Glover and Klingman's method for the associated linear program within a depth-first search procedure. A heuristic is used to find a starting dual feasible solution to the associated linear program and a ‘pegging’ test is employed to reduce the size of the problem for the enumeration phase. Computational experience and comparisons with the code of Nauss and an algorithm of Armstrong et al. for the same problem are reported.     

Study of 170,171,173Ta isotopes at high spinṡ

High-spin data are presented for ¹⁷⁰Ta and ¹⁷¹Ta for the first time, and the known level scheme of ¹⁷³Ta is extended to higher spins. Anomalies found in the crossing frequencies for the alignment of a pair of neutrons are considered. At high spin a large and constant value of J⁽²⁾, with J⁽²⁾ > J⁽¹⁾, is found for two ¹⁷¹Ta bands and the implications of this are discussed. The πi_13/2 [660]1/2⁺, α = + 1/2 orbital is identified as it crosses the rotational band built on the [402]5/2⁺, α = + 1/2 orbital in ¹⁷¹Ta. Magnetic transition probabilities obtained from measured branching ratios show the effects of the aligning pair of neutrons and the spectator orbital. The data are interpreted using cranked shell-model calculations and a semiclassical vector-coupling scheme developed by Donau and Frauendorf.