Properties of Gluon and Quark Jets

Recent developments and results on the comparison of gluon to quark jets are discussed. A most important topic is the introduction of explicit energy scales of the jets. The scaling violation of the fragmentation function and the increase of the multiplicity with scale is shown to be directly proportional to the corresponding gluon or quark colour factor. The ratio of the hadron multiplicity in gluon to quark jets is understood to be smaller than the colour factor ratio due to differences in the fragmentation of the leading quark or gluon. Novel algorithms to reconstruct the colour portraits or the colour flow of an event are presented

Tätigkeit, Qualifikation und gesundheitliche Verfassung. Ein differenziertes Informationssystem über Berufe

"Die Untersuchung beschäftigt sich mit der Erfassung und Analyse von Belastungen von Arbeitnehmern. Insofern Belastungen auch zu Arbeitsmarktrisiken werden können, ist ein deutlicher Bezug zur Diskussion des Beschäftigungsrisikos gegeben. Vorrangiges Ziel ist das Auffinden von Arbeitnehmergruppen und deren Struktur, und zwar von Gruppen, die als besonders belastet gelten können. Es galt unter dem Begriff der Belastung nicht nur Verhältnisse am Arbeitsplatz mit einzubeziehen, sondern auch diejenigen auf dem Arbeitsmarkt, das gesundheitliche Befinden der Arbeitnehmer und schließlich ihre Situation in der Freizeitsphäre. Die Daten aus diesen vielfältigen Untersuchungskomplexen sind aus verschiedenen Studien zusammengetragen worden. Um eine möglichst hohe Vergleichbarkeit zu gewährleisten, wurden alle Informationen auf den nach Geschlecht getrennten zweistelligen Berufsgruppenschlüssel des Statistischen Bundesamtes von 1961 aggregiert. Die dadurch entstandene Matrix (58 Berufsgruppen und 96 Variablen) ist mittels clusteranalytischer Verfahren ausgewertet worden. Im Ergebnis sind 8 Cluster von Berufsgruppen - quasi Berufsbereiche - gebildet worden. Dabei kann deutlich zwischen geschlechtsspezifischen Berufsgruppenclustern im industriellen Bereich und Clustern im tertiären Bereich unterschieden werden. Im industriellen Sektor sind die weiblichen Berufstätigen schwer belastet als die männlichen Arbeitnehmer. Im tertiären Bereich zeigen sich die Berufsgruppen nur unterdurchschnittlich belastet. Innerhalb jedes einzelnen Clusters erweist sich, daß sich die Informationen in den einzelnen Variablenkomplexen kumulieren: schlechte Bedingungen am Arbeitsplatz sind verbunden mit hohen Beschäftigungsrisiken und schlechten Freizeitverhältnissen und umgekehrt. Diesem Sachverhalt kann auf der sozialpolitischen Ebene nur nurch komplexe Maßnahmepakete abgeholfen werden."Arbeitsbelastung, Freizeitverhalten, Clusteranalyse, Arbeitssituation, Arbeitsmarktchancen, Gesundheit, Arbeitsmarktchancen

Determination of the Michel Parameters rho, xi, and delta in tau-Lepton Decays with tau --> rho nu Tags

Using the ARGUS detector at the $e^+ e^-$ storage ring DORIS II, we have measured the Michel parameters $\rho$, $\xi$, and $\xi\delta$ for $\tau^{\pm}\to l^{\pm} \nu\bar\nu$ decays in $\tau$-pair events produced at center of mass energies in the region of the $\Upsilon$ resonances. Using $\tau^\mp \to \rho^\mp \nu$ as spin analyzing tags, we find $\rho_{e}=0.68\pm 0.04 \pm 0.08$, $\xi_{e}= 1.12 \pm 0.20 \pm 0.09$, $\xi\delta_{e}= 0.57 \pm 0.14 \pm 0.07$, $\rho_{\mu}= 0.69 \pm 0.06 \pm 0.08$, $\xi_{\mu}= 1.25 \pm 0.27 \pm 0.14$ and $\xi\delta_{\mu}= 0.72 \pm 0.18 \pm 0.10$. In addition, we report the combined ARGUS results on $\rho$, $\xi$, and $\xi\delta$ using this work und previous measurements.Comment: 10 pages, well formatted postscript can be found at http://pktw06.phy.tu-dresden.de/iktp/pub/desy97-194.p

Energy dependence of Cronin momentum in saturation model for p+Ap+A and A+AA+A collisions

We calculate $\sqrt{s}$ dependence of Cronin momentum for $p+A$ and $A+A$ collisions in saturation model. We show that this dependence is consistent with expectation from formula which was obtained using simple dimentional consideration. This can be used to test validity of saturation model (and distinguish among its variants) and measure $x$ dependence of saturation momentum from experimental data.Comment: LaTeX2e, 12 pages, 8 figure

CP asymmetry in B→ϕKSB \to \phi K_S in a general two-Higgs-doublet model with fourth-generation quarks

We discuss the time-dependent CP asymmetry of decay $B \to \phi K_S$ in an extension of the Standard Model with both two Higgs doublets and additional fourth-generation quarks. We show that although the Standard Model with two-Higgs-doublet and the Standard model with fourth generation quarks alone are not likely to largely change the effective $\sin 2 \beta$ from the decay of $B \to \phi K_S$, the model with both additional Higgs doublet and fourth-generation quarks can easily account for the possible large negative value of $\sin 2 \beta$ without conflicting with other experimental constraints. In this model, additional large CP violating effects may arise from the flavor changing Yukawa interactions between neutral Higgs bosons and the heavy fourth generation down type quark, which can modify the QCD penguin contributions. With the constraints obtained from $b \to s \bar{s} s$ processes such as $B \to X_s \gamma$ and $\Delta m_{B_s^0}$, this model can lead to the effective $\sin 2 \beta$ to be as large as $- 0.4$ in the CP asymmetry of $B \to \phi K_S$.Comment: 13 pages, 5 figures, references added, to appear in Eur.Phys.J.

A Precise Measurement of the Tau Lifetime

The tau lepton lifetime has been measured with the e+e- -> tau+tau- events collected by the DELPHI detector at LEP in the years 1991-1995. Three different methods have been exploited, using both one-prong and three-prong tau decay channels. Two measurements have been made using events in which both taus decay to a single charged particle. Combining these measurements gave tau_tau (1 prong) = 291.8 +/- 2.3 (stat) +/- 1.5 (sys) fs. A third measurement using taus which decayed to three charged particles yielded tau_tau (3 prong) = 288.6 +/- 2.4 (stat) +/- 1.3 (sys) fs. These were combined with previous DELPHI results to measure the tau lifetime, using the full LEP1 data sample, to be tau_tau = 290.9 +/- 1.4 (stat) +/- 1.0 (sys) fs.Comment: 27 pages, 7 figure

Search for composite and exotic fermions at LEP 2

A search for unstable heavy fermions with the DELPHI detector at LEP is reported. Sequential and non-canonical leptons, as well as excited leptons and quarks, are considered. The data analysed correspond to an integrated luminosity of about 48 pb^{-1} at an e^+e^- centre-of-mass energy of 183 GeV and about 20 pb^{-1} equally shared between the centre-of-mass energies of 172 GeV and 161 GeV. The search for pair-produced new leptons establishes 95% confidence level mass limits in the region between 70 GeV/c^2 and 90 GeV/c^2, depending on the channel. The search for singly produced excited leptons and quarks establishes upper limits on the ratio of the coupling of the excited fermio

Search for lightest neutralino and stau pair production in light gravitino scenarios with stau NLSP

Promptly decaying lightest neutralinos and long-lived staus are searched for in the context of light gravitino scenarios. It is assumed that the stau is the next to lightest supersymmetric particle (NLSP) and that the lightest neutralino is the next to NLSP (NNLSP). Data collected with the Delphi detector at centre-of-mass energies from 161 to 183 \GeV are analysed. No evidence of the production of these particles is found. Hence, lower mass limits for both kinds of particles are set at 95% C.L.. The mass of gaugino-like neutralinos is found to be greater than 71.5 GeV/c^2. In the search for long-lived stau, masses less than 70.0 to 77.5 \GeVcc are excluded for gravitino masses from 10 to 150 \eVcc . Combining this search with the searches for stable heavy leptons and Minimal Supersymmetric Standard Model staus a lower limit of 68.5 \GeVcc may be set for the stau mas