Pion broadening and low-mass dilepton production

We determine mass and transverse momentum spectra of dileptons produced in Pb+Au (158 GeV/u) collisions within a pion annihilation model. A fit to the data requires simultaneous mass reduction and broadening of the in-medium rho propagator. The introduction of a finite pion width, as required within self-consistent approaches to the interacting pion gas, further improves the agreement with the data.Comment: 11 pages, 5 figure

Ensuring sustainability in supply chains: A competence model for purchasing professionals

Implementing sustainability into global supply chains remains a challenge for companies. Purchasing and Supply Management (PSM) interacts closely with supply network actors, thus influencing how the firm’s value creation is delivered. While previous sustainable PSM (SPSM) research has shed light on how to manage sustainability on an organisational level, the role and impact of individual purchasing professionals on SPSM is less well understood. Their contribution to SPSM depends on both: they must be qualified, and they must be allowed to integrate sustainability in their daily work. Models from organisational psychology consider individual competence as one determinant for behaviour in organisations, together with motivational factors and enablers through the organisation. Transferred to the SPSM context, competences of purchasing professionals contribute to sustainable behaviour in the organisation. This thesis set out to understand individual SPSM competences, with the aim to foster their integration in the daily work of purchasing professionals, finally contributing to the implementation of sustainability in supply chains. It strived for an answer to the central research question: “Which individual competences of PSM professionals are required to implement SPSM?”, with the objectives to develop a SPSM competence model and to design a SPSM training module. A multi-method approach rarely applied so far in the PSM field was used to gather SPSM competences. First, a systematic literature review (SLR) determined the current research coverage of SPSM competences. Second, a Delphi study was conducted with 16 experts in the field of PSM and sustainability, applying the critical incident technique (CIT). A systematic qualitative data analysis led to a set of 26 SPSM competences. These were consolidated in a competence model, highlighting functional, cognition-oriented, social and meta-oriented competences. Familiar denominations of competences were corroborated with specific descriptions in terms of their application in the specific SPSM context. Third, the SPSM competences were transferred into a training module, which was tested in an action research approach with students and purchasing professionals. The findings of this research help companies to better cope with the implementation of sustainability in global supply chains, as individual SPSM competences, being one major determinant of SPSM behaviour, are now much more transparent. Firms may use the competence model and the training module as blueprints and adapt them to the individual organisational context. For Higher Education, the thesis offers inspiration how to integrate sustainability into PSM curricula by focusing on the most important competence areas. In addition, by applying models from educational sciences and organisational psychology in the PSM context, the research intends to foster an interdisciplinary debate on SPSM competences. Finally, future research might look for answers to the hypothesis that SPSM competences point towards a general competence profile for PSM professionals that is necessary to be able to cope with future challenges in the field

Optomechanics with molecules in a strongly pumped ring cavity

Cavity cooling of an atom works best on a cyclic optical transition in the strong coupling regime near resonance, where small cavity photon numbers suffice for trapping and cooling. Due to the absence of closed transitions a straightforward application to molecules fails: optical pumping can lead the particle into uncoupled states. An alternative operation in the far off-resonant regime generates only very slow cooling due to the reduced field-molecule coupling. We predict to overcome this by using a strongly driven ring-cavity operated in the sideband cooling regime. As in the optomechanical setups one takes advantage of a collectively enhanced field-molecule coupling strength using a large photon number. A linearized analytical treatment confirmed by full numerical quantum simulations predicts fast cooling despite the off-resonant small single molecule - single photon coupling. Even ground state cooling can be obtained by tuning the cavity field close to the Anti-stokes sideband for sufficiently high trapping frequency. Numerical simulations show quantum jumps of the molecules between the lowest two trapping levels, which can be be directly and continuously monitored via scattered light intensity detection

Strange hadronic stellar matter within the Brueckner-Bethe-Goldstone theory

In the framework of the non-relativistic Brueckner-Bethe-Goldstone theory, we derive a microscopic equation of state for asymmetric and $\beta$-stable matter containing $\Sigma^-$ and $\Lambda$ hyperons. We mainly study the effects of three-body forces (TBFs) among nucleons on the hyperon formation and the equation of state (EoS). We find that, when TBFs are included, the stellar core is almost equally populated by nucleons and hyperons. The resulting EoS, which turns out to be extremely soft, has been used in order to calculate the static structure of neutron stars. We obtain a value of the maximum mass of 1.26 solar masses (1 solar mass $M_o \simeq 1.99 \cdot 10^{33} g$). Stellar rotations increase this value by about 12%.Comment: 4 pages, Latex, 2 figures included. To appear in the Proceedings of '' Bologna 2000 - Structure of the Nucleus at the Dawn of the Century'', May 29- June 3, 2000, Bologna, Ital

Structure of the hadron-quark mixed phase in protoneutron stars

We study the hadron-quark phase transition in the interior of hot protoneutron stars, combining the Brueckner-Hartree-Fock approach for hadronic matter with the MIT bag model or the Dyson-Schwinger model for quark matter. We examine the structure of the mixed phase constructed according to different prescriptions for the phase transition, and the resulting consequences for stellar properties. We find important effects for the internal composition, but only very small influence on the global stellar properties.Comment: 6 pages, 4 figure