Mats Bengtsson

The Lund Monte Carlo for jet fragmentation and e+ e- physics - jetset version 6.3 - an update

Abstract Title of program: JETSET 6.3 Catalogue number: AATJ Program obtainable from: CPC Program Library, Queens University of Belfast, N. Ireland (see application form in this issue) Computer for which the program is designed and others on which it is operable: ND, VAX, IBM, CDC and others with a FORTRAN 77 compiler Computer: ND-570; Installation: University of Lund, Lund, Sweden Operating system: SINTRAN III - VSX/500 Programming language used: FORTRAN 77 High speed storage required: 50 Kwords No. of bits in word: 32 Peripherals used: terminal for input, terminal or line printer for output No. of lines in combined program and test deck: 6173

Coherent Parton Showers Versus Matrix Elements: Implications of PETRA - PEP Data

Abstract Traditionally, matrix elements have been used to provide the probability for multijet configurations in e + e − annihilation events. Some serious discrepancies between PETRA/PEP data and event simulation programs based on this approach have been discovered by the JADE and Mark II Collaborations. Instead we develop here a new coherent parton shower algorithm, well matched on to the three-jet matrix element, which provides a better description of existing data, in line with the agreement previously obtained between data and the Marchesini-Webber coherent parton shower program. A very low cutoff for the patron shower evolution, in the order of 1 GeV, seems indicated. The conclusion is that events with many partons, more than are accessible with present-day matrix elements, play an important role already at CM energies of 30 GeV. For extrapolations to higher energies, like TRISTAN/SLC/LEP, parton showers therefore offer more reliable predictions.

A comparative study of coherent and non-coherent parton shower evolution

Abstract We present a new algorithm for the probalistic evolution of jet cascades, based on the leading log approximation to perturbative QCD, augmented by coherence studies. Compared to previous models, emphasis is put on expressing kinematical variables in terms of Lorentz invariants and on matching on to the three-jet matrix element in e + e − annihilation. A systematic study is made of various assumptions in the model, such as the implementation of kinematics, the choice of Q 2 scale and the inclusion of angular ordering. In particular, we address the issue of how to find experimental evidence for coherence effects.

On-line trace metal enrichment and matrix isolation in atomic absorption spectrometry by a column containing immobilized 8-quinolinol in a flow-injection system

Abstract Metal ions (Cu 2+ , Co 2+ , Cd 2+ , Ni 2+ , Pb 2+ , Zn 2+ ) were concentrated quantitatively and isolated from the sample matrix by a colum

Parton showers in leptoproduction events

We present a model that includes the production of arbitrarily many jets in lepton-hadron events, using the leading log formalism for parton shower evolution. The main problem encountered here, which has not previously been illuminated by studies ofe+e− annihilation or Drell-Yan/Z0/W± production, is the choice of kinematics in the space-like shower evolution. In our preferred solution, the standard definition of Bjorkenx is preserved during the construction of initial and final state showers—a nontrivial constraint. The resulting model is described in detail, including some first investigations of its properties.

Preconcentration and matrix isolation of heavy metals through a two-stage solvent extraction in a flow system

Abstract Metal ions (Cd, Cu, Pb, Co and Ni) in trace amounts were isolated from sample matrices and concentrated by extraction in a flow system. The sample flow was first mixed with buffer and reagent (carbamates) and the combined aqueous flow was next segmented with trichlorotrifluoroethane (Freon 113). The metal complexes were extracted into the organic phase in a 2-m long coil which was followed by a separator with a teflon membrane. The organic phase passed on to a second segmentor where an acidic, aqueous mercury(II) solution was added. Back-extraction to the aqueous solution took place in a 1-m long coil. The Freon was removed in a second membrane separator and the aqueous phase was collected and analyzed by graphite-furnace atomic absorption spectrometer. The enrichment factors were of the order of 15–20 and the recoveries were 90–100% from the sub-μg l −1 level up to 20–50 μg l −1 . The recoveries decrease at concentrations above 50 μg l −1 , presumably because of slow dissolution of precipitated complexes in the sample solutions. The observed recoveries for copper were generally somewhat lower, being in the range 80–90%.

Initial state radiation effects onW and jet production

A model for initial state parton showers, previously presented briefly, is here discussed in more detail. Experimentally, the transverse momentum spectrum ofW andZ, and the associated jet activity, are the most obvious signals for initial state radiation. We show that these effects are well described by our model, compare with analytic calculations, and discuss the uncertainty due to various open issues in the description of initial state radiation. Other subjects studied include radiation effects on jet cross sections and the transverse energy flow. Results are presented for a wide range of CM energies.

On-line dialysis of some metal ions and metal complexes

Abstract The effect of ionic strength, pH and complexing ligands on the dialysis of metal ions, particularly zinc(II), through cellulose acetate membranes, was studied under flow conditions. The dialysis factor, which depends on both the mass transfer and the membrane permeability, was found to be independence of ionic strength in the interaval 0.05–0.3 M and to increase only slightly with pH 4.6 and 7.0. Some common buffer constituents had no effect, but chloride and calcium ions affected the transfer rates. The rate of transfer of the ligands histidine, NTA and EDTA was of the same order of magnitude as that of the metal ions. The transfer rate of the Ni(II)-EDTA complex was the same as that of a mixture of Ni(II) and EDTA. Generally, addition of the chelating agents decreased the metal-ion transfer rates. Partition coefficients between the membrane polymer and the buffers were evaluated and compared with the dialysis factors and there were significant differences with regard to the range of variation, effect of concentration and pH-dependence. The time scale of uptake or release of metal ions by the polymer is much longer than that of a steady-state transfer in dialysis. Partition and dialysis may not be directly related to each other.

Trace metal ion preconcentration for Flame Atomic Absorption by an Immobilized N,N,N′-tri-(2-pyridyl-methyl)ethylene diamine (TriPEN) chelate ion exchanger in a flow injection system

SummaryTrace Metal Ion P reconcentration for Flame Atomic Absorption by an Immobilized N,N,N′-tri-(2-pyridylmetkyl)ethylene diamine (TriPEN) Chelate Ion Exchanger in a Flow Injection System Chelating groups of N,N,N′-tri-(2-pyridyl-methyl)ethyIene diamine (TriPEN) were synthesized on the surface of porous glass. A 100μl column of the chelate ion exchanger was incorporated into a flow injection manifold with a flame atomic absorption spectrometer. Metal ions from samples (<1 ml to>80 ml) were retained on the chelate ion exchanger until an injection of acid displaced them into the flame. A peak-shaped absorbance curve was recorded. The use of immobilized TriPEN for preconcentration of metals from dilute solution and for matrix modifications was demonstrated.

The effect of fragmentation models on the determination of αs from Hadron collider data

Abstract Recently, a number of α S determinations have been presented, based on the ratio of three-to two-jet events at ISR and the Sp p S Collider. The accuracy of these determinations is probably restricted more by uncertainties in the underlying theory than by experimental errors. It is shown that, as in e + e − annihilation, the use of different fragmentation models may lead to widely different α S values being reconstructed. For the analysis of ISR data, the spread may be up to a factor of two, which is reduced to roughly 20% at the higher Sp p S energies.