Search for Narrow NNpi Resonances in Exclusive p p -> p p pi+ pi- Measurements

Narrow structures in the range of a few MeV have been searched for in p p pi+ and p p pi- invariant mass spectra obtained from exclusive measurements of the p p -> p p pi+ pi- reaction at Tp = 725, 750 and 775 MeV using the PROMICE/WASA detector at CELSIUS. The selected reaction is particularily well suited for the search for NN and / or N Delta decoupled dibaryon resonances. Except for a possible fluctuation at 2087 MeV/c^2 in Mpppi- no narrow structures could be identified neither in Mpppi+ nor in Mpppi- on the 3 sigma level of statistical significance, giving an upper limit (95% C.L.) for dibaryon production in this reaction of sigma < 20 nb for 2020 MeV/c^2 < m(dibaryon) < 2085 MeV/c^2Comment: 3 pages, 4 figure

Magnets for the national spallation neutron source accumulator ring

The National Spallation Neutron Source Accumulator Ring will require large aperture dipole magnets, strong focusing quadrupole magnets, and smaller low field dipole, quadrupole, and sextupole correcting magnets. All of the magnets will provide a fixed magnetic field throughout the accumulator`s fill/storage/extraction cycle. Similar fixed field magnets will also be provided for the beam transport systems. Because of the high intensity in the accumulator, the magnets must be designed with high tolerances for optimum field quality and for the high radiation environment which may be present at the injection/extraction areas, near the collimators, and near the target area. Field specifications and field plots are presented as well as planned fabrication methods and procedures, cooling system design, support, and installation

Study of the p p -> p p pi+ pi- Reaction in the Low-Energy Tail of the Roper Resonance

Exclusive measurements of the p p -> p p pi+ pi- reaction have been carried out at Tp = 775 MeV at CELSIUS using the PROMICE/WASA setup. Together with data obtained at lower energy they point to a dominance of the Roper excitation in this process. From the observed interference of its decay routes N* -> N sigma and N* -> Delta pi -> N sigma their energy-dependent relative branching ratio is determined

Reallabore im Kontext transformativer Forschung : Ansatzpunkte zur Konzeption und Einbettung in den internationalen Forschungsstand

Reallabore sind derzeit ein populärer Forschungsansatz an der Schnittstelle zwischen Wissenschaft und Gesellschaft. Neben vermuteten Potentialen, wie der Erzeugung von Transformationswissen und einem Beitrag zu gesellschaftlichem Wandel, gibt es auch vielfältige offene Fragen, u. a. im Hinblick auf das Verhältnis zu transdisziplinärer Forschung, der Übertragbarkeit des erzeugten Wissens oder der Gestaltung von Experimenten in der "realen Welt". Auch eine breit getragene Definition von Reallaboren existiert derzeit nicht. Dieses Diskussionspapier möchte daher dreierlei leisten: Es beginnt mit dem Herausarbeiten von Reallabor-Merkmalen als a) Beitrag zu Transformationsprozessen, b) Experimenten als zentraler Forschungsmethode, c) Transdisziplinarität als Forschungsmodus, d) dem Ziel der Ausweitung und Übertragung der Ergebnisse und e) Reallaboren als Orten wissenschaftlichen und gesellschaftlichen Lernens. Im Nachgang werden diese Merkmale durch Rückbezug auf die einschlägige Literatur vertieft diskutiert. Abschließend werden mit Reallaboren vergleichbare Forschungsansätze (Sustainable Living Labs, Urban Transition Labs und Niche Experiments) im Hinblick auf ihre Ausgestaltung der fünf herausgearbeiteten Merkmale vorgestellt und Reallabore damit in den internationalen Forschungskontext eingebettet. Das Diskussionspapier will damit Forschenden und Praktiker_innen in Reallaboren eine Orientierung ermöglichen. Die vorgestellten konzeptionellen Überlegungen basieren auf einem thematischen Literatur-Review, ebenso wie Diskussionen mit Reallabor- und Transformationsforschenden in nationalen und internationalen Kontexten. Sie sind im Rahmen der Begleitforschung des Forschungsprojektes "ForReal" zu den Baden-Württembergischen Reallaboren entstanden. Dem Charakter eines Diskussionspapieres entsprechend sind die hier vorstellten Rahmungen zum Reallaboransatz als Angebot zur Diskussion, Erweiterung und Verbesserung zu verstehen

Shaping Real-World Laboratories by Comparing Them

Various experimental approaches of transformative research in real-world settings have emerged. Yet, similarities, differences, and specific contributions remain unclear. A characteristic-based comparison reveals complementarities and provides orientation. Real-world laboratories (RwLs, German Reallabore) belong to a family of increasingly popular experimental and transdisciplinary research approaches at the science-society interface. As these approaches in general, and RwLs in particular, often lack clear definitions of key characteristics and their operationalization, we make two contributions in this article. First, we identify five core characteristics of RwLs: contribution to transformation, experimental methods, transdisciplinary research mode, scalability and transferability of results, as well as scientific and societal learning and reflexivity. Second, we compare RwLs to similar research approaches according to the five characteristics. In this way, we provide an orientation on experimental and transdisciplinary research for societal transformations, and reveal the contributions of this type of research in supporting societal change. Our findings enable learning across the different approaches and highlight their complementarities, with a particular focus on RwLs

Design of the 26.7 MHz rf cavity for RHIC

The accelerating system for RHIC operates at 26.7 MHz (h = 342) and must capture the injected beam, accelerate it to top energy, and shorten the bunches prior to rebucketing into the storage (h = 2508) system. These different functions set the design parameters of the cavity. The frequency of 26.7 MHz has been chosen in order to provide large enough buckets to capture the injected beam from the AGS and a large linear region for debunching during a bunch rotation at top energy. Provision of the large linear region also dictates the voltage requirement of 400 kV per cavity. The cavity must be tuned {approximately}90 kHz to compensate for the change in speed of the gold beam

Observation of strong final-state effects in pi+ production in pp collisions at 400 MeV

Differential cross sections of the reactions $pp \to d\pi^+$ and $pp \to pn\pi^+$ have been measured at $T_p = 400$ MeV by detecting the charged ejectiles in the angular range $4^0 \leq \Theta_{Lab} \leq 21^\circ$. The deduced total cross sections agree well with those published previously for neighbouring energies. The invariant mass spectra are observed to be strongly affected by $\Delta$ production and $NN$ final-state interaction. The data are well described by Monte Carlo simulations including both these effects. The ratio of $pp \to pn\pi^+$ and $pp \to d\pi^+$ cross sections also compares favourably to a recent theoretical prediction which suggests a dominance of $np$-production in the relative $^3S_1$-state.Comment: 17 pages, 5 figure

d' dibaryon in a colored cluster model

The mass and wave function of a six-quark system with quantum numbers JP=0-, T=0, called d′, are calculated. We use a colored diquark-tetraquark cluster model for the six-quark wave function. A constituent quark model Hamiltonian with a two-body confinement potential, and residual one-gluon, one-pion, and one-σ exchange interactions is used. The complications due to the quark exchange interactions between tetraquark and diquark clusters (Pauli principle) are taken into account within the framework of the resonating group method. The calculated d′ mass is some 350 MeV above the empirical value if the same two-body confinement strength as in the nucleon and Δ is used. This paper also examines the validity of the usual assumption of a universal two-quark confinement strength. We propose that the effective two-body confinement strength in an exotic six-quark system, such as the d′, could be weaker than in a single baryon. The weaker confinement hypothesis leads to a d′ mass of Md′=2092 MeV and a d′ radius of rd′=1.53 fm.A. J. Buchmann, Georg Wagner, and Amand Faessle