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The study of hidden charm production is an important part of the heavy ion program. The standard approach to this problem [1] assumes that c¯c bound states are created only at the initial stage of the reaction and then partially destroyed at later stages due to interactions with the medium [2, 3, 4].
Charmonium production and suppression in heavy-ion collisions at relativistic energies is investigated within di erent models, i.e. the comover absorption model, the threshold suppression model, the statistical coalescence model and the HSD transport approach. In HSD the charmonium dissociation cross sections with mesons are described by a simple phase-space parametrization including an e ective coupling strength |Mi|2 for the charmonium states i =Xc,J/psi, psi'. This allows to include the backward channels for charmonium reproduction by DD channels which are missed in the comover absorption and threshold suppression model employing detailed balance without introducing any new parameters. It is found that all approaches yield a reasonable description of J/psi suppression in S+U and Pb+Pb collisions at SPS energies. However, they di er significantly in the psi'/J/psi ratio versus centrality at SPS and especially at RHIC energies. These pronounced differences can be exploited in future measurements at RHIC to distinguish the hadronic rescattering scenarios from quark coalescence close to the QGP phase boundary.
We study the phase diagram of dense, locally neutral three-flavor quark matter within the framework of the Nambu--Jona-Lasinio model. In the analysis, dynamically generated quark masses are taken into account self-consistently. The phase diagram in the plane of temperature and quark chemical potential is presented. The results for two qualitatively different regimes, intermediate and strong diquark coupling strength, are presented. It is shown that the role of gapless phases diminishes with increasing diquark coupling strength.
Chats spielen im eLearning eine kontroverse Rolle: einerseits werden sie oftmals als virtuelle Plauderecken gesehen und es wird ihnen keine wesentliche Rolle in netzbasierten Bildungsangeboten zugesprochen, andererseits stellen sie in einigen virtuellen Veranstaltungsangeboten ein wichtiges Kommunikationselement dar und tragen zum sozialen Zusammenhang der lernenden Gruppe bei. Ob Chats im Rahmen von eLearning erfolgreich eingesetzt werden können, hängt von den Zielsetzungen der Veranstaltung, dem jeweiligen Kontext und den eingesetzten didaktischen Methoden ab. Es muss gelingen, die besonderen medialen Eigenschaften des Chats gewinnbringend in den Bildungsangeboten einzusetzen – wobei mit Gewinn nicht ein monetärer, sondern ein didaktischer Mehrwert bezeichnet wird. Dieser Beitrag widmet sich den Einsatzmöglichkeiten des Chats im eLearning: auf der Basis von Beispielen und Erfahrungen zum Einsatz dieses Mediums in virtuellen Hochschulveranstaltungen werden Gestaltungsempfehlungen abgeleitet und Anwendungsszenarien in der Hochschullehre und der beruflichen Bildung beschrieben.
Results from various theoretical approaches and ideas presented at this exciting meeting (summary talk at the 5th International Conference on Physics and Astrophysics of Quark Gluon Plasma (ICPAQGP - 2005)) are reviewed. I also point towards future directions, in particular hydrodynamic behaviour induced by jets traveling through the quark-gluon plasma, which might be worth looking at in more detail.
We calculate thermal photon and neutral pion spectra in ultrarelativistic heavy-ion collisions in the framework of three-fluid hydrodynamics. Both spectra are quite sensitive to the equation of state used. In particular, within our model, recent data for S + Au at 200 AGeV can only be understood if a scenario with a phase transition (possibly to a quark-gluon plasma) is assumed. Results for Au+Au at 11 AGeV and Pb + Pb at 160 AGeV are also presented.
In this paper we derive a formula for the energy loss due to elastic N to N particle scattering in models with extra dimensions that are compactified on a radius R. In contrast to a previous derivation we also calculate additional terms that are suppressed by factors of frequency over compactification radius. In the limit of a large compactification radius R those terms vanish and the standard result for the non compactified case is recovered.
We present a detailed study of chemical freeze-out in p-p, C-C, Si-Si and Pb-Pb collisions at beam momenta of 158A GeV as well as Pb-Pb collisions at beam momenta of 20A, 30A, 40A and 80A GeV. By analyzing hadronic multiplicities within the statistical hadronization model, we have studied the parameters of the source as a function of the number of the participating nucleons and the beam energy. We observe a nice smooth behaviour of temperature, baryon chemical potential and strangeness under-saturation parameter as a function of energy and nucleus size. Interpolating formulas are provided which allow to predict the chemical freeze-out parameters in central collisions at centre-of-mass energies > 4.5 GeV and for any colliding ions. Specific discrepancies between data and model emerge in particle ratios in Pb-Pb collisions at SPS between 20A and 40A GeV of beam energy which cannot be accounted for in the considered model schemes.
System-size dependence of strangeness production in nucleus-nucleus collisions at √sNN = 17.3 GeV
(2005)
Emission of pi, K, phi and Lambda was measured in near-central C+C and Si+Si collisions at 158 AGeV beam energy. Together with earlier data for p+p, S+S and Pb+Pb, the system-size dependence of relative strangeness production in nucleus-nucleus collisions is obtained. Its fast rise and the saturation observed at about 60 participating nucleons can be understood as onset of the formation of coherent partonic subsystems of increasing size. PACS numbers: 25.75.-q
Results are presented on Omega production in central Pb+Pb collisions at 40 and 158 AGeV beam energy. Given are transverse-mass spectra, rapidity distributions, and total yields for the sum Omega+Antiomega at 40 AGeV and for Omega and Antiomega separately at 158 AGeV. The yields are strongly under-predicted by the string-hadronic UrQMD model and are in better agreement with predictions from a hadron gas models. PACS numbers: 25.75.Dw
The cumulant method is applied to study elliptic flow (v_2) in Au+Au collisions at sqrt s=200 AGeV, with the UrQMD model. In this approach, the true event plane is known and both the non-flow effects and event-by-event spatial (epsilon) and v_2 fluctuations exist. Qualitatively, the hierarchy of v_2 's from two, four and six-particle cumulants is consistent with the STAR data, however, the magnitude of v_2 in the UrQMD model is only 60% of the data. We find that the four and six-particle cumulants are good measures of the real elliptic flow over a wide range of centralities except for the most central and very peripheral events. There the cumulant method is affected by the v_2 fluctuations. In mid-central collisions, the four and six-particle cumulants are shown to give a good estimation of the true differential v_2, especially at large transverse momentum, where the two-particle cumulant method is heavily affected by the non-flow effects.
Transverse hadron spectra from proton-proton, proton-nucleus and nucleus-nucleus collisions from 2 AGeV to 21.3 ATeV are investigated within two independent transport approaches (HSD and UrQMD). For central Au+Au (Pb+Pb) collisions at energies above E lab ~ 5 AGeV, the measured K +- transverse mass spectra have a larger inverse slope parameter than expected from the default calculations. The additional pressure - as suggested by lattice QCD calculations at finite quark chemical potential mu q and temperature T - might be generated by strong interactions in the early pre-hadronic/partonic phase of central Au+Au (Pb+Pb) collisions. This is supported by a non-monotonic energy dependence of v2/pT in the present transport model.
Die Driften der Wörter in öffentlichen Räumen sind vielfältig. Neue Wortentwicklungen belegen unterschiedliche Interessen, "chillen" und "dissen" andere als das in der konservativen Züricher Zeitung zuerst erschienene "share-holder-value". Im Folgenden soll eine sinnbezoge Verallgemeinerung unternommen werden, die die Handlungen der Akteure mit der strukturellen Ebene verbindet. Die Veränderungen in den Verwendungen sollen zu strukturellen sozialen und sprachlichen Rahmenbedingungen in Bezug gesetzt werden. Wie werden Neuerungen und Änderungen der Anwendungsbedingungen von Wörtern vor dem Hintergrund des Wissens um die traditionelle Standardsprache und deren soziale Funktion wahrgenommen? Welche Funktionen haben Neologismen in Abgrenzung zu diesem Standard?
In this paper, we investigate the usefulness of a wide range of features for their usefulness in the resolution of nominal coreference, both as hard constraints (i.e. completely removing elements from the list of possible candidates) as well as soft constraints (where a cumulation of violations of soft constraints will make it less likely that a candidate is chosen as the antecedent). We present a state of the art system based on such constraints and weights estimated with a maximum entropy model, using lexical information to resolve cases of coreferent bridging.
The work presented here addresses the question of how to determine whether a grammar formalism is powerful enough to describe natural languages. The expressive power of a formalism can be characterized in terms of i) the string languages it generates (weak generative capacity (WGC)) or ii) the tree languages it generates (strong generative capacity (SGC)). The notion of WGC is not enough to determine whether a formalism is adequate for natural languages. We argue that even SGC is problematic since the sets of trees a grammar formalism for natural languages should be able to generate is difficult to determine. The concrete syntactic structures assumed for natural languages depend very much on theoretical stipulations and empirical evidence for syntactic structures is rather hard to obtain. Therefore, for lexicalized formalisms, we propose to consider the ability to generate certain strings together with specific predicate argument dependencies as a criterion for adequacy for natural languages.
The causative/anticausative alternation has been the topic of much typological and theoretical discussion in the linguistic literature. This alternation is characterized by verbs with transitive and intransitive uses, such that the transitive use of a verb V means roughly "cause to Vintransitive" (see Levin 1993). The discussion revolves around two issues: the first one concerns the similarities and differences between the anticausative and the passive, and the second one concerns the derivational relationship, if any, between the transitive and intransitive variant. With respect to the second issue, a number of approaches have been developed. Judging the approach conceptually unsatisfactory, according to which each variant is assigned an independent lexical entry, it was concluded that the two variants have to be derivationally related. The question then is which one of the two is basic and where this derivation takes place in the grammar. Our contribution to this discussion is to argue against derivational approaches to the causative / anticausative alternation. We focus on the distribution of PPs related to external arguments (agent, causer, instrument, causing event) in passives and anticausatives of English, German and Greek and the set of verbs undergoing the causative/anticausative alternation in these languages. We argue that the crosslinguistic differences in these two domains provide evidence against both causativization and detransitivization analyses of the causative / anticausative alternation. We offer an approach to this alternation which builds on a syntactic decomposition of change of state verbs into a Voice and a CAUS component. Crosslinguistic variation in passives and anticausatives depends on properties of Voice and its combinations with CAUS and various types of roots.
Von der welt louff vnd gestallt (3b) [Anm. 1] - vom Lauf der Welt und ihrem Zustand - handelt ein Werk, das im Zentrum der nachfolgenden Überlegungen stehen soll: die Reimchronik zum Schwaben- bzw. Schweizerkrieg des Hans Lenz vom Jahr 1499. In Form eines fiktiven Gesprächs, einer disputatz (62b) zwischen dem Autor und einem Waldbruder, werden die historische Zeitgeschichte und die damalige politisch-gesellschaftliche Situation gesichtet, geordnet, diskutiert, gedeutet und in größere, insbesondere heilsgeschichtliche Zusammenhänge gebracht. Text und Kontext stehen in diesem Beispiel (wie in der Historiographie ganz allgemein) in besonders offensichtlicher Beziehung zueinander - es leuchtet unmittelbar ein, daß ein solcher Text ohne den geschichtlichen Hintergrund nicht angemessen beurteilt werden kann. Dabei darf allerdings nicht allein danach gefragt werden, wie der Historiograph mit den geschichtlichen Fakten (soweit diese überhaupt objektiv rekonstruiert werden können!) umgeht, es muß auch dem Umfeld des Verfassers selbst und seiner Rezipienten sowie dem Zweck und der Funktion seiner Dichtung Rechnung getragen werden, den literarischen und außerliterarischen Einflüssen und Vorbildern, den Denk- und Argumentationsmustern, kurz: die "Lebenswelt" [Anm. 2] des Textes sollte zu seinem Verständnis im gesellschaftlich-kulturellen Kontext soweit als möglich erschlossen werden.
Eine Reihe von nicht in Kodifikationen des Standards aufgenommenen sprachlichen Mustern wird im Blick auf ihre Karrieren in verschiedenen mündlichen und schriftlichen Texten in einer Flut von Veröffentlichungen thematisiert, meist in der Hoffnung hier grammatische Entwicklungen und die Basis für eine Orientierung der Grammatikschreibung an der Pragmatik zu entdecken. Im Folgenden soll Sprache nicht „konzeptuell schriftlich“ gedacht und „sozusagen literal idealisiert“ werden. Es soll argumentiert werden für eine einheitliche, mit Sprachgeschichte, ontogenetischem Spracherwerb und Variantenbildung verträgliche Erklärung nicht-standardisierter sprachlicher Muster im Rahmen einer Grammatikalisierungstheorie.